Alcatel-Lucent B12 BSS Overview

Alcatel-Lucent BSS

Alcatel-Lucent BSS Components

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Legend:

GP

GPRS Processing Unit

External Components Overview

The Alcatel-Lucent BSS communicates with three external components: •

The NSS, on the A Interface

•

The mobile station, on the Air Interface

•

The OMC-R, on the BSS/OMC-R Interface.

The following figure shows the logical position of the external components.

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Alcatel-Lucent BSS

External Components

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Figure 2-2 Logical Position of External Components Associated with BSS

Legend:

GGSN

Gateway GPRS Support Node

HLR

Home Location Register

MFS

Multi-BSS Fast Packet Server

NMC

Network Management Center

PSDN

Packet Switched Data Network

PSTN

Public Switched Telephone Network

SGSN

Serving GPRS Support Node

Network Subsystem

The primary role of the NSS is managing communication within the PLMN and external networks. The NSS manages the subscriber administration databases. .................................................................................................................................................................................................................................... Alcatel-Lucent BSS 9YZ-03803-1802-TQZZA B12 Issue 4 October 2012

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External Components

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An NSS comprises: •

The Mobile Switching Center (MSC), which co-ordinates outgoing and incoming call set up for GSM subscribers for voice and other user traffic

•

The Home Location Register (HLR), which is the central database within a given network for mobile subscriber-specific data

•

The Visitor Location Register (VLR), which temporarily stores information about the mobile stations entering its coverage area

•

The Authentication Center (AUC), which manages the security data used for subscriber authentication

•

The Equipment Identity Register (EIR), which contains the lists of mobile station equipment identities.

To handle (E)GPRS data traffic, the NSS also includes: •

The Serving (E)GPRS Support Node (SGSN), which handles packet (i.e. data) traffic, including security functions, and the interface to the HLR

•

The Gateway (E)GPRS Support Node (GSGN), which provides interworking with external packet-switched networks.

The following figure shows the components of a typical NSS.

Legend:

AUC

Authentication Center

EIR

Equipment Identity Register

GGSN


HLR

Home Location Register

MSC

Mobile Switching Center

SGSN


VLR

Visitor Location Register

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External Components

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Outgoing inter-PLMN handovers allow operators to define handover adjacency links towards external cells belonging to foreign PLMNs (to which external OMC-R cells belong). The Multi-PLMN feature allows operators to define several PLMNs in order to support network sharing, inter-PLMN handovers and cell reselections between two different PLMNs. The BSC cannot be shared and therefore remains mono-PLMN (i.e. all BSC cells belong to the same PLMN). This feature defines several PLMNs, inter-PLMN handovers, and cell reselections between two different PLMNs. New BSC counters as well as Outgoing Inter-PLMN handovers monitor procedures involving all types of inter-PLMN handover. Mobile Stations

Mobile stations provide radio and processing functions which allow subscribers to access the mobile network via the Air Interface. Subscriber-related information is stored on a specific device called a SIM. Each mobile station has its own International Mobile Equipment Identity (IMEI). The IMEI is used by the Network Operator to prevent stolen or non-type approved mobile stations from accessing the network. There are three types of mobile station in GSM: •

Phase 1

•

Phase 1 extended

•

Phase 2.

For information about GPRS mobile stations, refer to “GPRS Elements” (p. 3-6). Mobile stations have different capabilities according to the class of mobile station and the purpose for which the mobile station was designed. These differences include power output and ciphering. Only phase 2 mobile stations can turn off ciphering, or change the ciphering mode, during a channel change procedure such as a handover. The ciphering capability of a mobile station is signalled to the BSS in the mobile station classmark. Ciphering is used to protect information transmitted on the Air Interface. This is performed between the BTS and the mobile station (i.e., Air Interface). Transmission ciphering does not depend on the type of data to be transmitted (i.e., speech, user data, signaling), but on normal transmission bursts. For more information about mobile station ciphering capabilities, refer to “Ciphering” (p. 5-51). Mobile Station Idle Mode

A mobile station is in idle mode when it is switched on but not communicating with the network on an SDCCH or a traffic channel. .................................................................................................................................................................................................................................... Alcatel-Lucent BSS 9YZ-03803-1802-TQZZA B12 Issue 4 October 2012

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Network Interworking

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Three scenarios are possible: •

without DTM

•

with DTM but without DTM HO support

•

with DTM HO support.

DTM is supported in ALU BSS while DTM HO is not. The third scenario is then not relevant for ALU BSS. This feature implements a mean for the BSS to reject LTEto GSM handovers, based upon the target cell load (similar to what has been already implemented for 3G to GSM handovers); this is the 'load based filtering' procedure. With the introduction of this feature, the BSC either accepts or rejects a handover from a LTE network, based on its own traffic load and the handover cause. If the load exceeds the threshold defined for the LTE network, only emergency handovers are allowed. The threshold is set from the OMC-R THR_CELL_LOAD_LTE_REJECT parameter. This must be set smaller than HIGH_TRAFFIC_LOAD parameter or equal to 100%. This feature is supported only on 9130 BSC Evolution and it is not optional. Interworking with LTE in Packet Domain

LTE (Long Term Evolution) is the evolution of 3G UMTS which targets very high throughputs. LTE means: •

No more CS plane, voice is carried through VoIP

•

A flat IP architecture

•

Use of enhanced radio techniques, including MIMO & OFDM

•

E-UTRAN the equivalent of GERAN (2G) or UTRAN (3G) is a set of eNodeBs connected to the same MME (Mobility Management Entity, part of the Core Network).

The purpose of the Inter-working with LTE in the Packet domain feature is to manage 2G versus LTE inter-working (in other words, the GERAN versus E-UTRAN inter-working), with the following requirements: •

Support of 2G to LTE-FDD reselection

•

GERAN CS User Plane is not managed (no CS Handover to be managed)

•

Inter-RAT NACC is managed for the E-UTRAN to GERAN direction only

•

Manage cell reselection in blind search mode.

The management of the reselection algorithm by the MS/UE takes into account additional parameters (the so-called priority parameters ) which are not only related to E-UARFCNs, but also to UARFCNs and 2G serving cells.

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Contents ....................................................................................................................................................................................................................................

Temporary Block Flow ......................................................................................................................................................... 3-18 3-18 Mobility Management

3-19 3-19 ..........................................................................................................................................................

Enhanced Packet Cell Reselection Paging

3-22 3-22 ...................................................................................................................................

3-25 3-25 .........................................................................................................................................................................................

Radio Power Control and Radio Link Measurement

33-26 -26 ................................................................................................3-26

Additional GRPS Network Functions

Resource Management Timeslott Allocation Timeslo

3-27 3-27 .........................................................................................................................................................

3-28 3-28 ...............................................................................................................................................................

Autonomous Packet Resource Allocation Packet Flow Context

3-29 .....................................................................................................................3-29

3-31 3-31 .............................................................................................................................................................

Dynamic Dyna mic Abis Allo Allocatio cation n

3-33 3-33 ....................................................................................................................................................

Enhanced Transmission Transmission Resource Management

33-36 -36 .........................................................................................................3-36

Frequency Hopping

3-36 3-36 ...............................................................................................................................................................

PCM Link Sharing

3-37 3-37 .................................................................................................................................................................

TBF Resource Re-allocation Dynamic Dyna mic Allo Allocatio cation n

3-37 3-37 ..............................................................................................................................................

3-39 3-39 ...............................................................................................................................................................

Extended Dynamic Allocation

3-39 3-39 ...........................................................................................................................................

Traffic Load Management

Overview of Traffic Load Management

3-40 ......................................................................................................................... 3-40

Smooth PDCH Traffic Adaption to Cell Load Variation Variation Congestion Control

33-40 -40 .........................................................................................3-40

3-41 3-41 ................................................................................................................................................................

M-EGCH Statistical Multiplexing GPRS Overload Control

3-41 3-41 ...................................................................................................................................

3-42 3-42 ......................................................................................................................................................

Data Transmission

Overview of Data Transmission GPRS Atta Attach ch

3-43 ........................................................................................................................................ 3-43

3-44 3-44 ............................................................................................................................................................................

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The feature targets the use of PC Data cards, this means pure PS data stream (VoIP stream is excluded). The GERAN/E-UTRAN inter-working feature is not relevant for an MS in DTM mode. Neighbouring information is broadcasted on the BCCH for MS in Dedicated Mode only and on the PACCH for MS in PTM mode only, as it is already the case for GERAN/UTRAN inter-working. Nothing is broadcasted for a MS in DTM mode. From B10 onwards, it is currently not possible to have UTRAN-FDD and UTRAN-TDD cell reselections enabled at the same time (as well as UTRAN-FDD HO and UTRAN-TDD cell reselection). A similar behaviour is kept with the introduction of E-UTRAN: to have either full FDD interoperability (UTRAN, E-UTRAN) or TDD interoperability. Neighbour E-UTRAN cells characteristics are broadcasted through the SI2 Quater message (same as for UTRAN cells). 3GPP introduced a new inter-RAT cell selection algorithm based upon priority information : •

The legacy algorithm is based upon cell ranking and already used for GERAN --> UTRAN inter-working. If for a given UTRAN cell all criteria are met during 5s then this cell is selected.

•

The priority algorithm allows to additionally prioritize RATs in order to favour for example E-UTRAN cells

•

The network provides priority information if E-UTRAN cells or frequencies are included within the neighbour cells list.

Therefore the BSS broadcast both legacy algorithm information and additional priority algorithm information. In the BSS, this mainly means new parameters to be sent to the MS (in SI2Quater or PMO), as this new algorithm is implemented on MS side. In SI2Quater message, all the parameters for the existing algorithm and the priority algorithm are sent. Then it is up to the MS to decide which algorithm to use in idle mode depending of its capabilities. For some cases in packet transfer mode, no Packet Measurement Order message is sent to a MS and in this case, the MS will use the parameters received in the SI2Quater message. Cell reselection towards 3G-FDD or towards 3G-TDD are mutually exclusive in B10 and B11 implementation. Both cannot be activated at the same time. The feature is supported only by 9130 MFS Evolution and 9130 BSC Evolution. The feature is optional and can be activated from OMC-R at cell level through EN_2G_TO_LTEFDD_CELL_RESELECTION parameter.

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The following rules apply when using this feature: •

The EN_2G_TO_3GTDD_CELL_RESELECTION and EN_2G_TO_LTEFDD_CELL_RESELECTION parameters cannot be enabled at the same time.

•

For a given BSS, we cannot have at the same time FDD_ARFCN_LIST defined at BSS level and, at least, one 2G cell where both EN_2G_TO_3G_CELL_RESELECTION and EN_2G_TO_LTEFDD_CELL_RESELECTION are enabled.

•

If both EN_2G_TO_3G_CELL_RESELECTION and EN_2G_TO_LTEFDD_CELL_RESELECTION are enabled, they must have the same value.

• EN_FAST_3G_CELL_RESELECTION cannot be set on 3 if any of EN_2G_TO_LTEFDD_CELL_RESELECTION or EN_2G_TO_3G_CELL_ RESELECTION is = 0 • EN_FAST_3G_CELL_RESELECTION cannot be set on 2 if EN_2G_TO_LTEFDD_CELL_RESELECTION = 0 •

MCC_LTE, MNC_LTE, CI_LTE uniquely identify an LTE cell inside the OMC. This represents the telecom/O&M LTE cell identification, also called ECGI (E-UTRAN Cell Global Identifier).

•

The allowed value ranges for ARFCN_LTE (FDD) are: [0..5379] U [5730..6599]. Note: For 2G-LTE interworking, Alcatel-Lucent recommends configuring ARFCN_LTE (FDD) value compliant with the values recommended by 3GPP release 9, where band 6 (2650 - 2749) is not applicable anymore and band 11 (4750 – 4999) is limited up to 4949.

For any given serving cell: •

No more than eight distinct values of ARFCN_LTE(FDD) are allowed in the neighbor LTE cells having RAT_LTE =FDD and targeted by 2g-LTE reselection links.

•

No more than 20 outgoing 2g-LTE adjacencies are allowed.

2G to LTE (TDD) Cell Re-selection

LTE (Long Term Evolution) is the evolution of 3G UMTS which targets very high throughputs. LTE means: •

No more CS plane, voice is carried through VoIP

•

A flat IP architecture

•

Use of enhanced radio techniques, including MIMO & OFDM

•

E-UTRAN the equivalent of GERAN (2G) or UTRAN (3G) is a set of eNodeBs connected to the same MME (Mobility Management Entity, part of the Core Network).


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The purpose of the 2G to LTE (TDD) Cell Re-selection feature is to manage 2G versus LTE inter-working (in other words, the GERAN versus E-UTRAN inter-working), with the following requirements: •

Support of 2G to LTE-TDD reselection

•

GERAN CS User Plane is not managed (no CS Handover to be managed)

•

Inter-RAT NACC is managed for the E-UTRAN to GERAN direction only

•

Manage cell reselection in blind search mode.

The management of the reselection algorithm by the MS/UE takes into account additional parameters (the so-called priority parameters ) which are not only related to E-UARFCNs, but also to UARFCNs and 2G serving cells. The feature targets the use of PC Data cards, this means pure PS data stream (VoIP stream is excluded). The GERAN/E-UTRAN inter-working feature is not relevant for an MS in DTM mode. Neighbouring information is broadcasted on the BCCH for MS in Dedicated Mode only and on the PACCH for MS in PTM mode only, as it is already the case for GERAN/UTRAN inter-working. Nothing is broadcasted for a MS in DTM mode. The following UTRAN/E-UTRAN FDD/TDD combinations are supported: Table 2-2

UTRAN/E-UTRAN FDD/TDD Supported Combinations 3G FDD

3G FDD

3G TDD

LTE FDD

LTE TDD

No

Yes

Yes

No

Yes

3G TDD

No

LTE FDD

Yes

No

LTE TDD

Yes

Yes

No No

Neighbour E-UTRAN cells characteristics are broadcasted through the SI2 Quater message (same as for UTRAN cells). 3GPP introduced a new inter-RAT cell selection algorithm based upon priority information : •

The legacy algorithm is based upon cell ranking and already used for GERAN --> UTRAN inter-working. If for a given UTRAN cell all criteria are met during 5s then this cell is selected.

•

The priority algorithm allows to additionally prioritize RATs in order to favour for example E-UTRAN cells

•

The network provides priority information if E-UTRAN cells or frequencies are included within the neighbour cells list.

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Therefore the BSS broadcast both legacy both legacy algorithm information algorithm information and additional priority additional priority algorithm information. algorithm information. In the BSS, this mainly means new parameters to be sent to the MS (in SI2Quater or PMO), as this new algorithm is implemented on MS side. In SI2Quater message, all the parameters for the existing algorithm and the priority the priority algorithm are algorithm are sent. Then it is up to the MS to decide which algorithm to use in idle mode depending of its capabilities. For some cases in packet transfer mode, no Packet Measurement Order message is sent to a MS and in this case, the MS will use the parameters received in the SI2Quater message. Cell reselection towards 3G-FDD or towards 3G-TDD are mutually exclusive in B10 and B11 implementation. Both cannot be activated at the same time. The feature is supported only by 9130 MFS Evolution and 9130 BSC Evolution. Evolution. The feature is optional and can be activated from OMC-R at cell level through through EN_2G_TO_LTETDD_CELL_RESELECTION EN_2G_TO_L TETDD_CELL_RESELECTION parameter parameter.. The following rules apply when using this feature: •

For a given BSS, we cannot have at the same same time TDD_ARFCN TDD_ARFCN_LIST _LIST defined defined at BSS level and, at least, one 2G cell where both EN_2G_TO_3GTDD_CELL_RESELECTION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled.

• EN_2G_TO_LTEFDD_CELL_RESELECTION and EN_2G_TO_LTETDD_CELL_RESELECTION cannot be enabled at the same time. •

If both EN_2G_TO_3G_ EN_2G_TO_3G_CELL_RESELECT CELL_RESELECTION ION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled, they must have the same value.

•

If both EN_2G_TO_3GT EN_2G_TO_3GTDD_CELL_RESEL DD_CELL_RESELECTION ECTION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled, they must have the same value.

• EN_FAST_3G_CELL_RESELECTION can be set on three, only if: – EN_2G_TO_3G_CELL_RESELECTION and EN_2G_TO_LTEFDD_CELL_RESELECTION are enabled or – EN_2G_TO_3G_CELL_RESELECTION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled or – EN_2G_TO_3GTDD_CELL_RESELECTION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled. • EN_FAST_3G_CELL_RESELECTION cannot be set on 2 if EN_2G_TO_LTEFDD_CELL_RESELECTION = 0 and EN_2G_TO_LTETDD_CELL_RESELECTION = 0. •

The allowed allowed value ranges for for ARFCN_ ARFCN_L LTE (TDD) are: are: [36000.. [36000.. 39649].


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•

•

For any given given serving serving cell, cell, no more more than n than n distinct distinct values of ARFCN_L ARFCN_LTE(TDD) TE(TDD) are allowed in the neighbor LTE cells having RAT_LTE =TDD and targeted by 2g-LTE reselection links, where n where n is: is: –

4, if EN_2G_TO_3GTD EN_2G_TO_3GTDD_CELL_RESEL D_CELL_RESELECTION ECTION and EN_2G_TO_LTETDD_CELL_RESELECTION are enabled on the aim serving cell and FAKE_FDD_MANA FAKE_FDD_MANAGEMENT GEMENT = 1 on the aim serving BSC

–

8, otherwise.

For any given serving cell, no more than 20 outgoing 2g-L 2g-LTE adjacencies are allowed.

GAN System

GANs extends extends the radio coverage coverage of 2G and 3G networks by allowing adapted dual mode (GSM/UMTS and GAN) mobiles to be connected to a 2G or 3G MSC through an unlicensed radio access (WIFI, Bluetooth). The GANC (GAN Controller) is connected to a legacy GSM/GPRS Core Network. In the GSM system, the GANC system interoperates with the 2G, through pseudo GAN cells. Each pseudo GAN cell allows the handover between the 2G and GANC (in charge of the real GAN system). system). A pseudo GAN GAN cell must be adjacent adjacent to the 2G cell. The MS decides when it is relevant to perform a handover and then the BSS executes the handover. There are no requirements on the packet side. Handover from a GAN cell to 2G has no impact on the BSS: •

Incoming External from GSM or from GAN The counters related to incoming external handovers take into account handovers coming from GAN and from GSM. No specific counters are provided for incoming handovers from GAN.

•

Outgoing External Outgoing External to to GSM or to GAN The counters related to outgoing external handovers take into account handovers to GAN in the same way as for GSM handove handovers. rs. No speci specific fic counters are provided for outgoing handover to GAN.

Iur-g Interface with Enhanced Control Plane

Iur is the interface defined by 3GPP between RNCs mainly to allow soft handover inside RNS (without involving CN) in the case of inter RNC handovers. The Iu interface with CN is kept unchanged after external handover and two RNCs (drift and serving) are involved in the call linked by Iur interface. The signaling protocol on Iur is named RNSAP (Radio (Radio Network Subsystem Application Part).

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A firs firstt step of simi similar lar interface interface named Iur-g between between BSCs and betwee between n RNC and BSC has been studied in 3GPP. Only some signalling information exchange between a BSS and a BSC/RNC has been standardized. The Iur-g interface is based on a subset of procedures and messages of the Iur interface of UTRAN, namely the RNSAP RNSAP.. Iur-g+ control plane is carried by SCCP/M3UA/SCTP/IP. Physical layer is IP only. With the current implementation, one BSC supports up to 16 neighbour RNCs. The new messages definition through an Iur-g like interface (Control plane) can optimize 3G to 2G Relocation/HO. Three procedures are defined on Iur-g+: •

Information Informatio n exchange procedure: procedure: in line line with 3GPP Iur-g Iur-g RNSAP RNSAP TS 25.423. The RNC obtains GSM cell capacity information from BSC.

•

Common Measurement Procedure: slightly modified procedure against against 3GPP Iur-g RNSAP TS 25.423 (more than one GSM cell per messages). messages). The RNC obtains GSM cell load indication from BSC. The availability of GSM target cell capacity and load allows the RNC to trigger a handover toward a GSM cell in which the handover will be probably successful.

•

Radio resource reserve handover procedure: specific procedure not defined in 3GPP, 3GPP, to reduce the handover preparation time and to trigger earlier the intersystem TD-SDCMA TD-SD CMA -> GSM handover in the UE. This procedure procedure allows the source RNC to request directly the BSC to allocate in advance the radio resource needed in the target BSS for a just triggered external TD -> GSM handover. This anticipation allows the RNC to trigger the handover command toward the UE earlier (before the receipt of RELOCATION COMMAND from CN). Consequently, the handover preparation time is reduced, and consequently the time critical intersystem handover has better probability to succeed.

The feature is optional, has one BSC-level activation parameter and is controlled per TRX quantity. The feature is activated from OMC-R, by setting the EN_IURG parameter on Enabled .


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3

3 GPRS in Alcatel-Lucent GPRS BSS

Overview Purpose

This section section provides an intr introducti oduction on to GPRS and describes how the Alcate Alcatel-Luc l-Lucent ent BSS implements: •

Packet Switching

•

GPRS Elements

•

GPRS Channels and Interfaces

•

GPRS Network Functions

•

GPRS Data Transmis Transmission. sion.

Contents Overview of GPRS in Alcatel-Lucent BSS

3-4

Packet Switching and GPRS Elements

3-4

Packet Switching

3-5

GPRS Elements

3-6

GPRS Channels and System Information Messages

3-10

Overview of GPRS Channels and System Information Messages

3-10

Logical Channels

3-10

Virtual Channels

3-11

System Information Messages

3-11

GPRS Interfaces

3-13

Overview of GPRS Interfaces

3-13

Gb Interface

3-13

BSCGP Interface

3-16

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3-1

GPRS in Alcatel-Lucent BSS

Overview

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GCH Interface

3-16

Specific LCS Interfaces

3-17

GPRS Network Functions

3-18

Overview of GPRS Network Functions

3-18

MAC and RLC Functions

3-18

Temporary Block Flow

3-18

Mobility Management

3-19

Enhanced Packet Cell Reselection

3-22

Paging

3-25

Radio Power Control and Radio Link Measurement

3-26

Additional GRPS Network Functions

3-27

Resource Management

3-27

Timeslot Allocation

3-28

Autonomous Packet Resource Allocation

3-29

Packet Flow Context

3-31

Dynamic Abis Allocation

3-33

Enhanced Transmission Resource Management

3-36

Frequency Hopping

3-36

PCM Link Sharing

3-37

TBF Resource Re-allocation

3-37

Dynamic Allocation

3-39

Extended Dynamic Allocation

3-39

Traffic Load Management

3-40


3-40

Smooth PDCH Traffic Ad A daption to Cell Load Variation

3-40

Congestion Control

3-41

M-EGCH Statistical Multiplexing

3-41

GPRS Overload Control

3-42

Data Transmission

3-43

Overview of Data Transmission

3-43

GPRS Attach

3-44

Packet Data Protocol Context Ac Activation

3-47

Data Transfer

3-51

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3-2


GPRS in Alcatel-Lucent BSS

Overview

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Packet Data Protocol Context De-activation

3-61

GPRS Suspend

3-66

GPRS Resume

3-68

GPRS Detach

3-71

Location Services

3-75

Overview of Location Services

3-75

Logical Architecture

3-76

LCS Positioning Methods

3-77

LCS Scenario in Circuit-Switched Domain

3-79

Physical Implementation

3-79

SMLC Functions

3-80

BSS and Cell Configuration

3-81

LCS O&M

3-81

High Speed Data Service

3-83

HSDS Description

3-83

GPRS CS3/CS4 and EGPRS Protocol

3-84

Transmission Handling

3-87

Cell/GP Mapping Modification

3-89

Gb over IP

3-90

Overview Gb over IP

3-90


3-3

Contents ....................................................................................................................................................................................................................................

Performance Management

Overview of Performance Management Traces

10-39 ......................................................................................................................10-39

10-40 10-40 .......................................................................................................................................................................................

Performance Monitoring

10-40 10-40 ...................................................................................................................................................

Radio Measurements Statistics

10-41 10-41 .......................................................................................................................................

Radio Measurements Statistics Improved Results Analysis

10-43 ................................................................................................................... 10-43

10-46 10-46 ...................................................................................................................................................................

Audits

Overview of Audits Audit Types

10-47 10-47 .............................................................................................................................................................

10-47 10-47 ............................................................................................................................................................................

Audit Flow .............................................................................................................................................................................. 10-49 10-49 Remote Inventory

Overview of Remote Inventory

10-50 10-50 ......................................................................................................................................

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GPRS in Alcatel-Lucent BSS Overview of GPRS in Alcatel-Lucent BSS

Packet Switching and GPRS Elements

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Overview of GPRS in Alcatel-Lucent BSS Packet Switching and GPRS Elements Overview

The success of GSM runs parallel to the explosion of interest in the Internet and related data services. Presently, Presently, data transmission over the Air Interface is limited to 9.6 kb/s, too slow for use of graphic-intensive services such as the World Wide Web and personal video conferences. In addition, the circuit-switched method used for data transmission makes inefficient use of radio resources, which are under increasing pressure from the growth in GSM subscribers and use. The solution solution chosen by the ETSI for the double challenge of increased demand for data service and pressure on radio resources is called General Packet Radio Service (GPRS). The ETSI recommendations establish a standard for inserting an alternative transmission method for data in the PLMN (packet switching instead of circuit switching). The Alcat Alcatel-Lu el-Lucent cent GPRS solut solution ion follows the ETSI GSM phase 2+ recom recommendat mendations ions closely.

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3-4



Packet Switching

....................................................................................................................................................................................................................................

Packet Switching Overview

In circuit switching, a connection is established and maintained during the entire length of the exchange, whether data is being transmitted or not. Resources are dedicated to a single end-to-end connection, and a radio channel in a cell, with its associated transmission channels, may be unavailable for use even when little or no information is passing across ac ross it at a given moment. In packet-switched systems, data is transmitted over virtual circuits, which exist only while data is actively being transmitted over them. This means that during idle time, timeslots can be used for carrying other data. Procedure

Packet-switching systems operate according to the following general procedures: ...................................................................................................................................................................................................

1

The PAD PAD function disassembles data into "packets" of a predefined size. ...................................................................................................................................................................................................

2

The PAD PAD encloses the packets in a data envelope (headers and footers). This data envelope includes information about origin and destination points, and the order in which the packet's contents are to be reassembled at the destination. The figure below shows a model of a GPRS Packet Data Unit at the LLC layer. ...................................................................................................................................................................................................

3

Packets move from origin to destination point by different routes and can arrive at the the destination in a different order than that in which they were sent. ...................................................................................................................................................................................................

4

At the destination, destination, another PAD PAD reads the envelope information, information, strips it off, off, and reassembles the data in the proper order. E................................................................................................................................................................................................... N D O F S T E P S


3-5


Packet Switching

....................................................................................................................................................................................................................................

Additional information Figure 3-1 Model LLC Packet Data Unit used in GPRS

Legend:

FCS

Frame Check Sequence

SAPI

Service Access Point Indicator

Examples of packet-switching protocols include X.25 and Internet Protocol. Since GPRS is compatible with these widely used protocols, it is suitable for access to public or custom packet data services, or to the Internet. Mobile telephones using packet data services must be connected to a portable computer or an electronic organizer.

GPRS Elements Overview

The different elements shown in the figure below represent a parallel system to the circuit-switched system used in GSM until now.

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3-6



GPRS Elements

....................................................................................................................................................................................................................................

Figure 3-2 The Alcatel-Lucent GPRS Solution in the PLMN

Legend:

BSCGP BSC GPRS Protocol FRDN

Frame Relay Data Network

GCH

GPRS Channel

GGSN


MFS


PSTN


SGSN


VLR

Visitor Location Register

In the Alcatel-Lucent solution, the MFS with its associated interfaces is the BSS element. All other components are external to the BSS. This section describes the following internal and external components: •

GPRS mobiles

•

The Serving GPRS Support Node

•

The Gateway GPRS Support Node

•

The Multi-BSS Fast packet Server.

This section describes the following internal and external components:


3-7


GPRS Elements

....................................................................................................................................................................................................................................

GPRS Mobiles

There are three classes of GPRS capable mobile stations: Class A, Class B, and Class C. Currently, only Class B and C mobile stations are supported: • Class A Class A mobile stations can handle circuit-switched voice and GPRS traffic simultaneously. •

•

Class B Class B mobile stations can be IMSI attached and GPRS attached at the same time, but use only one service (circuit switched or packet switched) at a time. A GPRS-attached Class B mobile station can initiate an IMSI connection and suspend its GPRS service in the following cases:

–

When the user is not engaged in any GPRS data transfer, and either: □ A mobile station-originated call is initiated □ The mobile station receives a mobile-termination call.

–

When the user is engaged in a GPRS session (e.g., an Internet session), and either: □ A mobile station-originated call is initiated □ The mobile station receives a mobile-termination call.

–

The mobile station performs a LAU procedure in network mode II or network mode III.

Class C Class C mobile stations can be either IMSI-attached or GPRS-attached, but not both, and can use circuit-switched or GPRS services alternately.


The SGSN is a GPRS network entity at the same hierarchical level as the MSC. It is external to the BSS and communicates with it via Frame Relay over the Gb Interface. The SGSN is involved in requesting specific network resources for GPRS traffic. It performs GPRS paging, authentication, and cipher setting procedures based on the same algorithms, keys and criteria as in circuit-switched GSM traffic. When a mobile station wants to access GPRS services, it makes its presence known to the network by performing a GPRS Attach procedure. This establishes a logical link between the mobile station and the SGSN. The mobile station is then available for SMS over GPRS, paging from the SGSN, and notification of incoming GPRS data. The SGSN also participates with other network elements in the routing and relaying of packets from one node to another. One SGSN can be connected to many MSCs and many MFSs.

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3-8



GPRS Elements

....................................................................................................................................................................................................................................


The GGSN is connected to SGSNs via an IP-based backbone. It provides interworking between the GPRS network and an d external packet-switched pack et-switched networks. It is external to the BSS. When the mobile station sends or receives GPRS data, it activates the Packet Data Protocol address that it wants to use. This has the effect of making the mobile station known to the GGSN. User data is transferred transparently from the mobile station and external data systems by the GGSN using encapsulation and tunnelling. This allows data packets equipped with GPRS-specific protocol information to be transferred between the mobile station and GGSN, in turn reducing the requirement for the GPRS system to interpret external data protocols. The GGSN also works with other network elements in the routing and relaying of packets from one node to another. Multi-BSS Fast Packet Server

For more information about the MFS, refer to the “Multi-BSS the “Multi-BSS Fast Packet Server” (p. 2-13). 2-13).


3-9

GPRS in Alcatel-Lucent BSS GPRS Channels and System Information Messages

Overview of GPRS Channels and System Information Messages

....................................................................................................................................................................................................................................

GPRS Channels and System Information Messages Overview of GPRS Channels and System Information Messages Overview

GPRS traffic uses the same radio resources as circuit-switched traffic, and is carried on the same type of physical channel. When a physical channel is allocated to carry packet logical channels (using TDMA frames, as does circuit-switched traffic), traffic), it is called a Packet Data Channel, or PDCH.

Logical Channels Overview

The types of logical channels which can be carried on a PDCH are the: •

Packet Traffic Channel

This channel is analogous to a circuit-switched traffic channel, and is used for user data transmission and its associated signaling. It has two sub-channels: –

Packet Data Traffic Channel which contains the user data traffic

–

Packet Associated Control Channel (bi-directional) which contains the signaling information. If multiple PDTCHs are assigned to one mobile station, the PACCH is always allocated alloca ted on one of the PDCHs on which PDTCHs are allocated. allocated. The function of these sub channels is analogous to their circuit-switched counterparts.

•

Packet Tim Timing ing Advanc Advancee Control Control Channe Channell. This bi-directional channel is used for maintaining a continuous timing advance update mechanism.

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3-10



Virtual Channels

....................................................................................................................................................................................................................................

Virtual Channels Overview

Packet switching is a mode of operation adapted to transmission of "bursty" data - that is, data which comes in intense "bursts" separated by periods of inactivity. The network establishes a connection during the transmission of such a "burst" of data. If there is no activity on this connection, the connection is taken down. When the original user needs to send or recei receive ve another burst of data, a new temporary temporary connection is set up. This can be on another channel in the same cell, or in another cell if the mobile station is in motio motion. n. The routi routing ng of one burst of data may be dif different ferent from the routing of another. The establishment and disestablishment of temporary connections is transparent to the user. The user sees an exchange of data that seems to be a continuous flow, unless the network is over congested. This semblance of continuous flow is a Virtual Channel. A virtu virtual al channel can be repre represented sented as the flow of data between two terminals terminals during a user session. The user has the impression of a single continuous connection, but in the network, networ k, this is not the case. A singl singlee data transfer, transfer, either in the uplin uplink k or in the downlink direction, direction, can pass between the MFS and the mobile mobile station via via one or more PDCH. A PDCH is shared shared between multiple mobile stations and the network. It contains asymmetric and independent uplink and downlink channels.

System Information Messages Overview

GPRS system information messages, like their GSM counterparts, transmit information about the cell to the mobile station. GSM BCCH messages, shown in Table in Table 2-1, “System Information Messages” (p. 2-44), 2-44), are also used in GPRS. In addition, GPRS also uses the messages shown in the following tables. Message

Channel

Information

SI 13

BCCH

The SI 13 message is sent on the BCCH and contains all the necessary information required for GPRS. It also indicates the presence and the location of the PBCCH in the serving cell. The SI 13 message is broadcast only if GPRS is supported in the cell.


3-11



....................................................................................................................................................................................................................................

Message

Channel

Information

SI 2quater

BCCH

The SI 2quater message is sent on the BCCH during 2G to 3G cell reselection and contains information about: •

3G cells

•

3G measurement parameters

•

GPRS 3G measurement parameters, parameters, when there is no PBCCH.

....................................................................................................................................................................................................................................

3-12


GPRS in Alcatel-Lucent BSS GPRS Interfaces

Overview of GPRS Interfaces

....................................................................................................................................................................................................................................

GPRS Interfaces Overview of GPRS Interfaces Overview

This section describes the GPRS interfaces, and in particular, the new interfaces introduced intro duced for GPRS needs needs.. These interfaces interfaces link the MFS and the SGSN, the BTS, and the BSC.

Gb Interface Overview

The Gb Interface uses frame relay techniques to link the PCU function of the MFS and the SGSN. Physically, it can be routed in a variety of ways: •

A direc directt connection connection betwee between n the MFS and and the SGSN

•

Via a public Frame Relay Data Network

•

Via the MSC

•

Via the Ater Mux Interfac Interfacee through the Transc Transcoder oder to the MSC. In this case, case, it carries carries a combination of packet-switched and circuit-switched traffic and signaling

•

Via the IP Network.

Combinations of these methods are also possible. See Figure See Figure 3-2, “The Alcat Alcatel-Lu el-Lucent cent GPRS Solution Solution in the PLMN” (p. 3-7) 3-7) for for the position of the Gb Interface in the system. The Gb Interface provides end-to-end signaling between the MFS and the SGSN, and serves as the BSS-GPRS backbone. Its principal functions are shown in the following table. Function

Description

Network services

Transfer of BSSGP-PDUs between the BSS and the SGSN Allocation and load sharing of PDUs among Virtual Channels Access to intermediate Frame Relay Data Network


3-13


Gb Interface

....................................................................................................................................................................................................................................

Function

Description

BSS-GPRS Protocol services

Radio resource information Quality of Service Information Routing information Transfer of LLC-PDUs between the BSS and the SGSN Suspend and Resume procedures for Class B mobile stations

Gb over IP With the introduction of GBoIP, the telecom traffic, towards/from the SGSN, goes through the router from/in the MFS. For a 9130 Evolution MFS the following rules apply: •

O&M one LAN: O&M/Telecom flows are using the same IP interface. This is the default topology. O&M/Telecom flows use a different IP interface.

•

O&M two LAN: The case of a same IP interface used for O&M/Telecom flows is not supported. The case of different IP interfaces used for O&M/Telecom flows is not recommended.

Gb Flex •

Gb Flex feature feature allows allows a BSS to be connected connected to more than one one SGSN.

• Terminology. The terminology is as follows: –

IP Endpoint An endpoint is defined defined by its IP address and UDP port. port. An IP endpoint endpoint can be a data endpoint, endpoint, a signa signalling lling endpoint endpoint or a pre-configured pre-configured endpoint. endpoint. An IP endpoint may be concomitently data and signaling endpoint. □ Data IP Endpoint An IP endpoint used for Data traffic. (Data traffic for an IP Sub-Network is defined as NS SDUs for PTP functional entities). □ Signalling IP endpoint An IP endpoint used for signalling traffic. (Signalling traffic for an IP Sub-Network is defined as NS SDUs for Signalling functional entities (BVCI = 0), PTM functional entities (BVCI = 1) and all PDUs for IP Sub-Network Service Control). Pre-configured IP endpoint An IP endpoint used to exchang exchangee the configuration configuration between between the BSS and the SGSN. Only IP V4 endpoints endpoints are supported. supported.

–

NS-VC

....................................................................................................................................................................................................................................

3-14


Introduction to GSM

GSM Background

....................................................................................................................................................................................................................................

2G is short for second-generation wireless telephone technology. The main difference to previous mobile telephone systems, retrospectively dubbed 1G, is that the radio signals that 1G networks use are analog, while 2G networks are digital. 3G is the generation of mobile phone standards and technology after 2G. It is based on the International Telecommunication Union (ITU) family of standards under the International Mobile Telecommunications programme, "IMT-2000". 3G technologies enable Network Operators to offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. 3G networks are wide area cellular telephone networks which evolved to incorporate high-speed internet access and video telephony. Both 2G and 3G systems use digital signaling to connect radio transmission towers to the rest of the telephone system. 2G technology encompasses: •

GSM

• GPRS •

EDGE ((E)GPRS)

•

EDGE Evolution.

3G technology includes the Universal Mobile Telecommunications System (UMTS), which is sometimes know as 3GSM, in order to emphasize the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed. The GSM working group based their system on digital transmission technology because digital transmission provides greater reliability, higher traffic density, and better quality than earlier analog methods. The original GSM recommendation specified a common frequency band around 900 MHz for mobile communication. Systems using this band are referred to as GSM 900 systems. To provide additional coverage in densely populated urban areas, a second band around 1800 MHz/1900 MHz was reserved. This is referred to as GSM 1800/1900 and uses the same GSM standards operating at the higher frequency range. The GSM 900 systems have been extended into the 900 MHz primary band (P-GSM band) and the 900 MHz extension band (G1 band). The GSM 850 MHz band was introduced in Release 1999 of the 3GPP Standard in 1999, but is supported by all mobile station releases since 1997, to allow operators to progressively replace the D-AMPS and CDMA technologies that were using these frequencies. For more information about GSM frequency ranges, refer to: •

“Channels” (p. 1-11)

•

“Frequency Band Configurations” (p. 2-3).

....................................................................................................................................................................................................................................

1-2



Gb Interface

....................................................................................................................................................................................................................................

The NS-VC (Network Service Virtual Connection) is given by a pair of IP endpoints endpoi nts at the MFS and SGSN.

•

–

Network Service Entity Identifier (NSEI) NSEI is an identifier of an NS Entity having end-to-end significance across the Gb interface, i.e. the peer NSEs on the BSS side and the SGSN side are identified by the same NSEI value.

–

BVC entity A BVC is a virtual virtual end-to-end end-to-end path path between between BSSGP peer peer entities entities.. A BVC is identified by a BVCI which is unique in one NSE and has an end-to-end significance across the Gb interface. There are two types of BVCs: Point-To-Point (PTP) BVC devoted to the GPRS traffic of one cell (BVCI>1) Signalling BVC, which is the signalling circuit of all the BVC-PTPs of one NSE (BVCI=0).

–

Pool area A pool area is an area within which a MS may roam without need to change the serving servi ng CN node. A pool area is is served by one or more more CN nodes in in parallel. parallel. All the cells controlled by a BSC belong to the same one (or more) pool area(s). One pool area can be served by one or several SGSNs. One BSS can belong to several pool areas. The granularity in a pool area is the BSS.

–

Pool-Area and Network Resource Identification An MS is served by one dedicated CN node of a pool-area as long as it is in radio coverage of the pool-area.

–

Null-NRI A 'null 'null-NRI -NRI'' indicates to the MFS that the NAS Node Selection Selection Function shall be used for selecting selecting a SGSN to recei receive ve a mess message. age. There is one unique 'null-NRI' 'null-NRI' in a PLMN supporting pool functionality.

–

NAS Node Selection Function In the BSS, the function selects the specific CN node (i.e. SGSN) to which initial NAS signalling messages or LLC frames are routed.

–

Off-loaded There are situations where a network operator will wish to remove load from one CN node in an orderly manner (e.g. to perform scheduled maintenance, or, to perform load re-distribution to avoid overload) with minimal impact to end users and/or additional load on other entities.

When Gb Flex is applied, applied, one or more SGSN serve serve a pool-area, pool-area, but only one out of these SGSN serves each individual MS.


3-15


BSCGP Interface

....................................................................................................................................................................................................................................

BSCGP Interface Overview

The BSCGP Interface provides communication between the BSC and the MFS (see Figuree 3-2, “The Alcate Figur Alcatel-Luc l-Lucent ent GPRS Solution Solution in the PLMN” (p. 3-7)). 3-7)). The BSC GPRS Protocol controls two LAPD connections (for redundancy) using 64 kb/s timeslots. The BSCGP Interface carrier following information. Function

Description

Common Commo n radio sign signaling aling

Circuit-sw Circu it-switch itched ed and packe packet-swi t-switched tched pagi paging ng (MFS to BSC) Channel Requests from BSC to MFS Uplink and downlink channel assignment (MFS to BSC)

GPRS radio resource management

Allocation/de-allocation of resources (MFS to BSC) Release indication (BSC to MFS) Load indication: this limits the allocation for GPRS traffic (BSC to MFS)

Note: The common radio signaling signaling funct functions ions of the BSCGP are handled on the GPRS Signaling Signal ing Link, which is carri carried ed inside the Ater Interface. Interface.

GCH Interface Overview

The GCH Interface provides a synchronous connection between the MFS and the BTS, using one to five 16 kb/s timeslots. The GCH links pass transparently through the BSC (see Figure (see Figure 3-2, “The Alcat Alcatel-Lu el-Lucent cent GPRS Solution Solution in the PLMN” (p. 3-7)). 3-7)). Its functions are as follows: •

Transfer of PDUs between the MFS MFS and the BTS. (Therefore, (Therefore, packet data is not directly handled by the BSC but passes transparently through it on the GCH interface.)

•

Synchronization with the the radio interface interface at GCH link establishment

•

Correction Corre ction of clock drifts drifts between between Abis and and BTS clocks. clocks.

The protocol for the GCH Interface uses the two layers described below: •

L1-GCH Layer

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3-16



GCH Interface

....................................................................................................................................................................................................................................

L1-GCH is the physical layer based on ITU-T recommendations G.703. The L1-GCH layer uses digital transmission at a rate of 2048 kbit/s with a frame of 32 x 64 kbit/s timeslots. times lots. An L1-GCH channel has a trans transmiss mission ion rate of 16 kbit/s. •

L2-GCH Layer L2-GCH L2-GC H is the data link layer which is an Alcat Alcatel-Lu el-Lucent cent proprietary proprietary protocol. protocol. This layer is in charge of the data transfer of the GCH frames between the MFS and the BTS. The L2-GCH layer offers a service of data transport for the RLC/MAC layers located in the MFS. Its main functions are:

–

GCH link establishment and release

–

Synchronization with the radio interface

–

RLC/MAC PDUs transfer transfer..

For more information about GSM transmission, refer to Chapter to Chapter 5, “Call Set Up”. Up”. The M-EGCH (Multiplexed-EGCH) link is available. The M-EGCH is a link established between the MFS and the BTS and is defined per TRX. An M-EGCH is made up of one to 36 GCHs. The M-EGCH link of a TRX carri carries: es: •

TBF traffic when TBFs are established established on the PDCHs of the TRX

•

TBF signaling messages messages on the TBF PACCH PACCH

•

MFS-BTS control messages

•

Uplink signaling messages messages after one-block allocation (in UL two-phase access).

Specific LCS Interfaces Overview

For LCS, the following specific interfaces are used: • SAGI Supports the exchange of messages between SMLC and the external GPS server following an Assisted GPS positioning request request in the circuit-switched domain • RRLP(BSCLP) Supports Suppor ts the exchang exchangee of mess messages ages between BSC and the SMLC (i.e., MFS) in the circuit-switched domain.


3-17

GPRS in Alcatel-Lucent BSS GPRS Network Functions

Overview of GPRS Network Functions

....................................................................................................................................................................................................................................

GPRS Network Functions Overview of GPRS Network Functions Overview

This section describes various GPRS-specific network functions necessary for successful packet data transfer. This includes paging, cell reselection, error checking and re-establishment, as well as radio power control and link measurement.

MAC and RLC Functions Overview

Since multiple mobile stations can be competing for the same physical resource(s), an arbitration procedure is necessary. This is provided by the Medium Access Control (MAC) function. The MAC function operates between the MFS and the mobile station, and works in conjunction with the Radio Link Control (RCL) function. RCL defines the procedures for retransmission of unsuccessfully delivered data blocks (error correction) and for the disassembly and reassembly of PDUs.

Temporary Block Flow Overview

When PDUs need to be transferred between the MFS and the mobile station, a temporary point-to-point physical connection is set up to support the unidirectional transfer of PDUs on one or more PDCHs. This connection is called a Temporary Block Flow (TBF). A TBF is maintained only for the duration of the data transfer. The TBF is allocated radio resources on one or more PDCHs and comprises a number of RLC/MAC blocks carrying one or more PDUs. A typical user session, in which data is exchanged bi-directionally, requires the establishment of one TBF in each direction. The path of each TBF can be different.

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3-18



Mobility Management

....................................................................................................................................................................................................................................

Mobility Management Overview

The GPRS Mobility Management (GMM) activities related to a GPRS subscriber are characterized by the following states: State

Description

Idle

In idle mode, the subscriber is not attached to the GPRS MM and therefore not known to the different GMM entities. The GMM context holds no valid location or routing information for the subscriber.

GMM Ready

When the mobile station starts the GPRS attach procedure, the mobile station enters the GMM Ready state to request access to the network.

GMM Standby

When the GMM Ready timer expires or is de-activated by the network, the mobile station returns to GMM Standby state.

Cell Reselection Modes

Network-controlled reselection modes are defined below. Mode

Description

NC0

A GPRS mobile station performs autonomous cell reselection without sending measurement reports to the network.

NC1

A GPRS mobile station performs autonomous cell reselection. Additionally, when it is in the GMM Ready state, it periodically sends measurement reports to the network.

NC2

A GPRS mobile station in GMM Ready state does not perform autonomous cell reselection. When in GMM Ready state, it sends measurement reports to the network that controls the cell reselection. NC2 is used only from R'4 MS.

Error Checking

Since the integrity of the data transmitted is crucial, packet-switched networks employ a method of error checking. This confirms that the data received corresponds exactly to the data transmitted. In GPRS, an LLC-PDU includes a Frame Check Sequence used to detect errors in the header and information fields of the PDU (see Figure 3-1, “Model LLC Packet Data Unit used in GPRS” (p. 3-6)). The Frame Check Sequence uses the Cyclic Redundancy Check method of error checking. .................................................................................................................................................................................................................................... Alcatel-Lucent BSS 9YZ-03803-1802-TQZZA B12 Issue 4 October 2012

3-19


Mobility Management

....................................................................................................................................................................................................................................

Most of the mobile stations use non-acknowledged LLC transmission (which can be incompatible with TCP). Error detection is done at the RLC level. In the case of cell reselection, the Alcatel-Lucent BSS retransmits the last LLC-PDU if all its RLC blocks were not acknowledged. Mobility Management Process

Mobility Management in GPRS can be accomplished by the combination of autonomous cell reselection by the mobile station and packet error correction. The process is as follows: ...................................................................................................................................................................................................

1

The mobile station performs an autonomous cell reselection. The process is based on average measurements of received signal strength on the BCCH frequencies of the serving cell and the neighbor cells as indicated in the GPRS neighbor cell list. This refers to NC0. The cell reselection procedure is the same as for circuit-switched traffic, but based on GPRS reselection parameters that can be configured by the operator. If the cell does not have a PBCCH, the mobile station applies existing circuit switching parameters using the BCCH. ...................................................................................................................................................................................................

2

Once the mobile station is camped on the new cell, the data transfer is resumed. If an LLC-PDU has not been correctly received, it is re-emitted. E................................................................................................................................................................................................... N D O F S T E P S

Overview

This process produces a slight overhead on throughput but has the advantage of greatly simplifying the cell change process. Link Re-establishment

If the mobile station detects a radio link failure, it will re-establish the link with the SGSN. The BSS transmits the reselection configuration parameters to be used by the mobile station. Mobile-controlled reselection is equivalent to circuit-switched call re-establishment. Refer to “Overview of Call Re-establishment by Mobile Station” (p. 6-54) for more information.

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3-20



Mobility Management

....................................................................................................................................................................................................................................

Full Intra-RA LLC-PDU Rerouting

This feature is implemented for a cell handled by another GP when there is an absence of information about the target cell to which the mobile station moves. The BSS links the old and new cells, using the information they have in common for that mobile station, namely the TLLI and the RAI. Once this link is set up, the BSS reroutes data from the old cell to the new cell. The BSS autonomously decides to perform LLC-PDU rerouting on a cell change when the SGSN does not support the Inter-NSE Rerouting (INR) R4 option. If the SGSN supports this option, then autonomous rerouting does not occur. NC2 for Mobile Stations in Packet Transfer Mode

To reduce the number of cell reselections, the mobile station in packet transfer mode does not make autonomous reselections. It sends measurement reports to the network, therefore NC2 mode is selected.


3-21



....................................................................................................................................................................................................................................

Enhanced Packet Cell Reselection Overview

In addition to enhanced cell reselection for R97-onwards MS, packet cell reselection is further improved with the following new features: •

Network Assisted Cell Change

•

Packet SI Status and Packet PSI Status procedures

•

NC2 Cell ranking with load criteria.

Enhanced Cell Reselections for R97 Onwards Mobile Stations

NC2 mode is activated when the mobile station enters the packet transfer mode and NC2 mode is de-activated either at the end of the packet transfer mode or at GMM Ready timer expiry (O&M parameter) This reduces the number of cell reselections triggered during GPRS sessions. When this feature is activated, the BSS prevents multi-RAT mobile stations from monitoring 3G cells while in packet transfer mode. This allows network control of mobile station cell reselection in packet transfer mode. NC2 for mobile stations in packet transfer mode is activated by O&M. When activated, the network controls cell reselection of each mobile station in a packet data transfer. Each of these mobile stations periodically reports its measurements to the serving cell and on the six strongest neighbor cells. This enables the network to decide whether or not an NC cell reselection is performed and which neighbor cell is the best candidate for reselection. This feature reduces the number of cell reselections triggered when the mobile station is in packet transfer mode. Network Assisted Cell Change

Network Assisted Cell Change (NACC) is a one of the new features implemented to reduce the duration of packet cell reselection. With NACC, control of cell reselection can be managed by the either the MS or the network, if NC2 mode is not being used. NC2 has priority over NACC. With the introduction of RIM-NACC, GPRS service outage during Inter-BSS or Inter-RAT PS cell reselection can also be improved. NACC takes place in the serving cell and consists of the following independent procedures: •

Cell Change Notification

•

Cell System Information Distribution.

NACC is enabled/disabled by the EN_NACC parameter.

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3-22




....................................................................................................................................................................................................................................

An MS supports Cell Change Notification (CCN) under the following conditions: •

CCN is activated in the (P)SI

•

The MS is not in Dedicated Mode or Dual Transfer Mode

•

The MS is in NC0 mode

•

The MS is in packet transfer mode.

Procedure

If the MS fulfills these conditions, when it detects a best new cell, using CCN: ...................................................................................................................................................................................................

1

The MS informs the BSS it wants to move from serving cell A to target cell B. ...................................................................................................................................................................................................

2

The BSS sends the required system information for the target cell on the PACCH. For a target cell without PBCCH, the SI13, SI1 and SI3 messages contain the required information. For a target cell with PBCCH, system information is contained in PSI14, PSI1 and PSI2. ...................................................................................................................................................................................................

3

The BSS also returns either a Packet Cell Change Continue or a Packet Cell Change Order message to the MS. ...................................................................................................................................................................................................

4

If the MS receives a Packet Cell Change Continue message, it switches to the previously selected target cell B. If the MS receives a Packet Cell Change Order message, the CCN procedure ends and the BSS (in NC2 mode) takes control of cell reselection using the Cell System Information Distribution procedure. The Packet Cell Change Order message is sent to the MS when the MS-selected target cell does not correspond to the target cell selected by the BSS. ...................................................................................................................................................................................................

5

Upon receipt of the Packet Cell Change Order message, the MS starts a timer and sends a Channel_Request message to the network-selected target cell. ...................................................................................................................................................................................................

6

When the MS receives a successful response to its Channel_Request message, along with the necessary system information, the MS switches to the new target cell. E................................................................................................................................................................................................... N D O F S T E P S


3-23

Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

The Alcatel-Lucent BSS supports the E-GSM band: •

The 900 MHz primary band (P-GSM band, 890-915 MHz in uplink, 935-960 MHz in downlink), and

•

The 900 MHz extension band (G1 band, 880-890 MHz in uplink, 925-935 MHz in downlink).

The following table shows all the supported frequency bands and the number of channels for each band. Table 1-2

GSM Channel Characteristics

Parameter

GSM 850

GSM 900

GSM 1800

GSM 1900

Transmit band

869 - 894 MHz

925 - 960 MHz

1805 - 1880 MHz

1930 - 1990 MHz

Receive band

824 - 849 MHz

880 - 915 MHz

1710 - 1785 MHz

1850 - 1910 MHz

Number of channels

124

174

374

299

The radio carriers are separated by 200 kHz. Each radio carrier is divided over time to give an eight timeslot frame. This is a Time Division Multiple Access (TDMA) frame. In TDMA, the callers are assigned timeslots as they are needed, and their signals are interleaved within the one channel as the sequence is transmitted. A channel uses a particular timeslot at each occurrence of a frame. (E)GPRS traffic uses the same radio resources as circuit-switched traffic, and is carried on the same type of physical channel. There are two types of GSM radio channels: •

Traffic Channels (TCH)

•

Control Channels (CCH).

Traffic Channels

TCHs are used as speech traffic channels (for ciphered speech) or as data traffic channels. Speech traffic channels are defined as: •

Half-rate traffic channels which use half a timeslot, at a rate of 6.5 kbits/s

•

Full-rate traffic channels which use a full timeslot, at a rate of 13 kbits/s

•

Enhanced full-rate traffic channels which use a full timeslot, at a rate of 13 kbits/s, but offer better speech quality.

For more information, refer to “Traffic Channels” (p. 2-40). Control Channels

A CCH carries signaling information and channel control information. Control channels have individual functions and operate at different rates. ....................................................................................................................................................................................................................................

1-12




....................................................................................................................................................................................................................................

Packet PSI Status and Packet SI Status Messages

The Packet PSI and Packet SI Status feature is implemented to reduce the amount of time required for GPRS cell reselection. This feature allows an MS to access a new cell without first receiving the full set of (P)SI messages sent on the BCCH (for SI messages) or the PBCCH (for PSI messages). The MS only has to read the information needed for GPRS operations in the target cell. The necessary GPRS information is contained in the following (P)SI messages: • SI13 •

SI3

•

SI1 (for SI, only if present; for PSI only if the PBCCH is hopping)

• PSI1 • PSI2 After receiving the necessary information, the MS sends the appropriate status message (PACKET PSI STATUS or PACKET SI STATUS) to the BSS. This status message tells the BSS what information the MS received in the earlier (P)SI messages. The BSS then sends the remaining SI messages needed by the MS on the PACCH if the MS has not returned to the packet idle state. If the MS has returned to the packet idle state, the MS can read the missing SI messages itself. The new EN_PSI_STATUS parameter is used to enable/disable: •

Packet SI Status in cells without BCCH

•

Packet PSI Status in cells with PBCCH.

Cell Ranking with Load Criteria

In NC2, cell ranking with load criteria avoids directing mobile stations towards high loaded cells. This reduces the possibility of an MS being served with non-optimum resources or being rejected due to congestion. The following two parameters control cell ranking with load criteria. This parameter...

Is used to...

EN_NC2_LOAD_RANKING

Enable/disable ranking the load of the target cell during NC2 cell ranking.

THR_NC2_LOAD_ RANKING

Set the threshold above which a cell is considered to be in a PS high load situation for NC2 cell reselection.

....................................................................................................................................................................................................................................

3-24



Paging

....................................................................................................................................................................................................................................

Paging Overview

Paging is the procedure by which the network contacts a mobile station. The network can co-ordinate circuit-switched and packet-switched paging if there is a Gs Interface between the MSC and the SGSN. This means that circuit-switched paging messages can be sent on the channels used for packet-switched paging messages, and vice-versa. Three modes are defined. Table 3-1

Network Operation Modes

Mode

Description

Network Operation Mode 1

Circuit-switched paging messages are sent via the SGSN and MFS. The circuit-switched paging message for the GPRS-attached mobile station is sent on the PPCH or CCCH paging channel, or on the PACCH. This means that the mobile station only needs to monitor one paging channel. It receives circuit-switched paging messages on the PACCH when the mobile station is in packet transfer mode.


Circuit-switched paging messages are sent via the MSC and BSC, but not the MFS. The circuit-switched paging message for the GPRS-attached mobile station is sent on the CCCH paging channel. The channel is also used for packet-switched paging messages. This means that the mobile station only needs to monitor the PCH. Circuit-switched paging continues on the PCH even if the mobile station is assigned a PDCH.


Circuit-switched paging messages are sent via the MSC and BSC, but not the MFS. The circuit-switched paging message for the GPRS-attached mobile station is sent on the CCCH paging channel. The packet-switched paging message is sent on either the PPCH (if allocated) or on the CCCH paging channel.

Packet-switched paging does not use the Local Area for paging, but a GPRS Routing Area (RA). The RA is smaller, and fewer cells are involved. For VGCS, Notification messages are broadcast periodically in the cell, on NCH, and optionally on FACCH, for ongoing point-to-point calls, to notify the VGCS mobile station of a new VGCS call being established.


3-25


Paging

....................................................................................................................................................................................................................................

This process is similar to the Paging procedure used for standard calls. Different notification procedures are applied, depending on the mode of the mobile station to be notified: •

Idle Mode Notification messages are broadcast on the NCH of the cell for new or ongoing VGCS calls

•

Group Receive Mode or Group Transmit Mode Notification messages are broadcast on the FACCH of other ongoing VGCS calls to notify the new VGCS calls that are being setup in the cell

•

Dedicated Group Transmit Mode Notification messages are broadcast on the FACCH of the dedicated TCH allocated to the talker

•

Dedicated Mode Notification messages are broadcast on the FACCH of all ongoing point-to-point calls in the cell to notify the new VGCS calls that are being setup in the cell.

Radio Power Control and Radio Link Measurement Overview

In order to decrease the level of interference in a network, the uplink and downlink transmissions are constantly measured and a balance is maintained between transmission power and the actual quality of the link. In GPRS, power control is implemented in an open loop on the uplink path. This maintains speech quality in the network and keeps a low bit error rate for data transmission. The BSS broadcasts the configuration parameters necessary for the mobile station. When it first accesses a cell, the mobile station sets its output power as defined in the system information. It then resets its power output according to the parameters broadcast, and to an evaluation of the uplink path loss.

....................................................................................................................................................................................................................................

3-26


GPRS in Alcatel-Lucent BSS Additional GRPS Network Functions

Resource Management

....................................................................................................................................................................................................................................

Additional GRPS Network Functions Resource Management Overview

In order to provide flexibility to the operator in managing the use of resources by circuit-switched and packet-switched traffic, resources are shared between the MFS and the BSC. Use of these resources by one system or the other can be controlled by a variety of parameters to meet operators' needs. The MFS and BSC co-ordinate resource management over the BSCGP Interface. In GPRS, resource management refers principally to the allocation of Packet Data Channels. PDCHs are dynamically allocated according to criteria that can be defined by the user. Procedure

When a TBF request is made, resources are allocated on one or more PDCH for the transfer of PDUs. The allocation process takes place as follows: ...................................................................................................................................................................................................

1

A TBF establishment request is received through a Packet Channel request for the uplink, or through a downlink LLC-PDU for the downlink. ...................................................................................................................................................................................................

2

The number of PDCHs is determined by the: •

Mobile station multislot class. This is not always known in the uplink case

•

O&M parameter ( MAX_PDCH_PER_TBF). This defines the maximum number of allocatable PDCHs per TBF.

...................................................................................................................................................................................................

3

If the requested number of PDCHs is not available, a request to establish a TBF is sent to the BSC. ...................................................................................................................................................................................................

4

PDCHs are allocated to the TBF. E................................................................................................................................................................................................... N D O F S T E P S


3-27


Timeslot Allocation

....................................................................................................................................................................................................................................

Timeslot Allocation Overview

GPRS allows bandwidth to be shared between several mobiles. On a radio timeslot, bandwidth can be shared between up to nine users on the downlink path and six on the uplink path, or up to 16 GPRS requests within one timeslot. Circuit-switched data services require at least one timeslot per user. The radio blocks on each timeslot are equally distributed among the users assigned to the channel. For example, on the uplink path when coding scheme 2 is used, the minimum raw bit rate per user is 1.9 kbit/s (13.4/7) instead of 13.4 kbit/s. The following table describes the parameters for timeslot allocation. This parameter:

Is used to:

MAX_UL_TBF_SPDCH

Define the maximum number of users (between one and six) that share a PDCH in the uplink direction.

MAX_DL_TBF_SPDCH

Define the maximum number of users (between one and nine) that share a PDCH in the downlink direction.

N_TBF_PER_SPDCH

Define the optimum number of shared users per direction and per PDCH. This ensures a good bit rate as long as the GPRS load is normal.

However, setting the N_TBF_PER_PDCH parameter ensures a compromise between resource efficiency and quality of service. For example, if N_TBF_PER_PDCH = 2 and coding scheme 2 is used, the preferred raw bit rate per user will be 6.7 kbit/s/s (13.4/2). When the number of users on the PDCH reaches the N_TBF_PER_PDCH value (2), the PDCH is declared "busy" and will preferably not accept a third user. But if the GPRS load is such that all PDCHs are busy, the BSS will override the number of users set in N_TBF_PER_PDCH and increase the number of shared resources to the maximum, using the MAL_XL_TBF_SPDCH value. For VGCS, a timeslot configured as a TCH timeslot is considered by the BSC to be a TCH timeslot reserved for VGCS and normal traffic when it is identified as TCH/SPDCH. When there are VGCS only timeslots available (configured but currently free) in the cell, these timeslots are used for VGCS. If there are no VGCS only timeslots available, the other free VGCS capable timeslots are used. Otherwise, VGCS calls are handled as normal calls and are managed using the same timeslot allocation strategy as for standard calls.

....................................................................................................................................................................................................................................

3-28




....................................................................................................................................................................................................................................

Autonomous Packet Resource Allocation Overview

Autonomous Packet Resource Allocation introduces a new way of sharing radio resources between the MFS and the BSC. With this feature, the MFS no longer needs to request radio timeslots from the BSC. Instead, the MFS is always aware of all the available timeslots. This speeds up PDCH establishment and decreases the BSC and MFS CPU loads. Because the MFS is aware of all available timeslots, the choice of the best allocation to serve the TBFs in the MFS is simplified. The SPDCHs are ordered by the BSC to ensure consistent circuit-switched and packet-switched allocation. The BSC ranks the PS TRXs and sends this ranking to the MFS on the BSCGP interface at cell creation and if the cell is modified during an O&M operation. The BSC defines the number of SPDCHs allocated to the MFS by computing the MAX_SPDCH_LIMIT. The resulting SPDCH allocation is based on the whole BSS load (CS plus PS load), with the PS load being provided periodically by the MFS. The BSC informs the MFS of the number of PS timeslots with the highest priority for PS traffic in the Radio Resource Allocation Indication message. Procedure

Autonomous Packet Resource Allocation works as follows: ...................................................................................................................................................................................................

1

The MFS periodically sends the BSC a Radio Resource Indication Usage message. This message contains the number of SPDCHs in the MFS and their use. ...................................................................................................................................................................................................

2

Upon receipt of this message, the BSC estimates the PS traffic load. Then, the BSC sends a Radio Resource Allocation Indication message providing the number of radio resources allocated to the MFS. ...................................................................................................................................................................................................

3

The MFS updates its SPDCH allocation table. If necessary, the MFS pre-empts a few SPDCHs in order to release them to the BSC. ...................................................................................................................................................................................................

4

The MFS sends a new Radio Resource Indication Usage message to the BSC acknowledging the new SPDCHs and indicating the de-allocated SPDCHs (if any). E................................................................................................................................................................................................... N D O F S T E P S


3-29



....................................................................................................................................................................................................................................

Autonomous Packet Resource Allocation Process

The following table shows the how the Autonomous Packet Resource Allocation uses a CS/PS resource-sharing concept with radio resources. A Timeslot Defined as....

Is...

Reserved for PS

Reserved for PS traffic only. The number of Reserved for PS timeslots is defined by the MIN_SPDCH parameter.

Priority for PS

Used for either CS or PS traffic, but PS traffic has priority. The number of Priority for PS timeslots is defined by the MAX_SPDCH_HIGH_LOAD and MIN_SPDCH parameters.

Priority for CS

Used for either CS or PS traffic, but CS traffic has priority. The number of Priority for CS timeslots available is the difference between the MAX_SPDCH and MAX_SPDCH_HIGH_LOAD parameters.

Reserved for CS

Reserved for CS traffic only. The number of Reserved for CS timeslots is defined by the MAX_SPDCH parameter.

This feature introduces a new parameter, MAX_SPDCH_LIMIT. It defines the number of SPDCHs that can be granted by the BSC to the MFS, and replaces the MAX-SPDCH_DYN parameter.

....................................................................................................................................................................................................................................

3-30



Packet Flow Context

....................................................................................................................................................................................................................................

Packet Flow Context Overview

The Packet Flow Context (PFC) provides end-to-end QoS management. It allows the BSS to differentiate between different types of traffic on the radio interface, by reading the QoS profiles listed in each PDP context defined by the subscriber. A PFC describes the QoS characteristics of ongoing data transmission. The BSS recognizes three QoS classes: •

The streaming class This class is a real-time stream and enforces jitter constraints. Video streaming and Push over Cellular (PoC) are typical applications.

•

The interactive class This class corresponds mainly to traditional Internet applications like web browsing.

•

The background class This class corresponds to Best Effort services such as e-mail downloading, SMS and ftp downloading.

When the PFC is activated, the BSS can reject or negotiate the QoS parameters in order to provide an optimum level of service by: •

Favouring conversational and streaming traffic over interactive and background traffic by reserving resources for these types of traffic This is particularly useful for subscribers who request a specific quality of service (QoS) profile for each PDP context, according to their requirements (for example, contexts associated with e-mail can tolerate lengthy response times, while other applications such as interactive real-time applications require a very high level of throughput).

•

Defining a flow aggregate based on the lifetime of the flows, in order to determine admission control and QoS based resource allocation in the BSS.

Procedure

In a basic case of mobile station initiated PDP context, PFC works as follows: ...................................................................................................................................................................................................

1

The mobile station defines the required QoS parameters and sends an Activate_PDP_Context_Request or a Modify_PDP_Context_Request message to the SGSN.


3-31


Packet Flow Context

.................................................................................................................................................................................................................................... ...................................................................................................................................................................................................

2

The SGSN determines the QoS it wants, based on: •

The QoS requested by the mobile station

•

The subscribed QoS stored in the HLR

•

Network QoS constraints.

The SGSN then performs internal call admission control and resource allocation. ...................................................................................................................................................................................................

3

The SGSN asks the GSGN to create the PDP context. ...................................................................................................................................................................................................

4

The GSGN performs internal call admission control and can eventually downgrade the QoS requested by the SGSN. ...................................................................................................................................................................................................

5

The SGSN uses the PFC feature to read and, if necessary, manage the QoS (for example, to downgrade resources when there is a cell change to a congested cell). ...................................................................................................................................................................................................

6

The SGSN informs the GSGN of any changes and informs the mobile station of the PDP context creation or modification, including the final QoS established in the network. E................................................................................................................................................................................................... N D O F S T E P S

Additional information Note: PFC can only be used if both the BSS and the SGSN support the feature.

For more information about PDP context management, refer to “Packet Data Protocol Context Activation” (p. 3-47).

....................................................................................................................................................................................................................................

3-32


Alcatel-Lucent BSS


....................................................................................................................................................................................................................................

In the 9130 BSC, the transmission equipment is replaced by virtual transmission processes, to ensure the same functions as in the 9120 BSC. For a more detailed description of the 9130 BSC, refer to the Alcatel-Lucent 9130 BSC Evolution Functional Description. Base Transceiver Station

The BTS provides the radio transmission, control and baseband functions for a cell. The BTS also supports the Air Interface with the mobile stations. Alcatel-Lucent provides the following families of BTSs: BTS 9110, BTS 9100 (G3, G4, G5 TRE, MC TRX, MC TRDU) and distributed BTS (MC RRH TRX). Where TRX is the HW TRE Function. The BTS performs the following functions under the control of the BSC: The BTS performs the following functions under the control of the BSC: •

Transmit and receive functions

•

Antenna diversity

•

Frequency hopping

•

Radio channel measurements

•

Radio frequency testing

•

Antenna Hopping.

The BTS also includes BIEs which enable it to communicate with the BSC over the Abis Interface. In the BTS 9100 and BTS 9110, the BIE is integrated into the SUM. For a more detailed description of the BTS and its use, refer to the: •

Alcatel-Lucent 9100 / 9110 Base Station / Micro Base Station - 9100 BTS/9110 Micro BTS Functional Description

•

Alcatel-Lucent 9153 Operation & Maintenance Center Radio - O&M Parameters Dictionary.

Antenna Diversity

Antenna Diversity is a BTS feature that protects against multipath fading. This is achieved by duplicating the receive antenna and receive path up to the Frame Unit (FU) of the BTS (or the TRE for a BTS 9100 or BTS 9110). The Frame Unit (or TRE) uses the data burst which has the fewest errors. This increases the low-power mobile station range, thereby allowing larger cells. BTS 9100/9110 Antenna Diversity

Antenna diversity on the BTS 9100 or BTS 9110 duplicates the receive antenna and receive path up to the Frame Unit. The Frame Unit uses the data burst which has the fewest errors. This increases low-power mobile station range, therefore allowing larger cells and lowering infrastructure investment.

....................................................................................................................................................................................................................................

2-8




....................................................................................................................................................................................................................................

Dynamic Abis Allocation Overview

This feature dynamically allocates Abis nibbles among the different TREs used for PS traffic in a given BTS. That is, the telecom mapping of the Abis nibbles to the TREs in the BTS is done dynamically. This means that unused Abis nibbles on one timeslot can be switched to another timeslot as needed. Dynamic Abis allocation reduces the average number of Abis nibbles used for PS traffic. It allows a higher average Abis bandwidth per PDCH and increased BSC capacity in terms of TREs. With dynamic Abis allocation, some BTS configurations do not need a second Abis link. This feature simplifies the dimensioning of the Abis interface since TRX-level dimensioning is no longer needed. Dynamic Abis allocation works with M-EGCH statistical multiplexing (see “M-EGCH Statistical Multiplexing” (p. 3-41)). As a reminder, a GCH channel in an M-EGCH link corresponds to a 16k link between the MFS and the BTS and uses one Abis nibble plus one Ater nibble switched together in the BSC. When needed for PS traffic, the GCH channel is activated. When no longer in use, the GCH channel is de-activated. In order to activate GCH channels at the BTS, TREs must listen to the Abis nibbles to detect the GCH activation messages. With dynamic Abis allocation, the BSC, when requested by the MFS, performs Abis-Ater switching / de-switching. Abis-Ater switching allows the BSC to switch N 16k Abis nibbles to N 16k Ater nibbles (n > 1). Abis-Ater de-switching does the reverse, i.e., N 16k Ater nibbles are switched for N 16k Abis nibbles. In conjunction with dynamic Abis allocation, the process also uses “Abis Nibble Pools” (p. 3-33) and a new “Abis Resource Manager” (p. 3-34). Abis Nibble Pools

Dynamic Abis allocation uses logical pools of Abis nibbles. An Abis nibble pool is a set of basic and extra Abis nibbles which can be dynamically allocated among TREs. The nibbles of a given pool can only be used by a fixed set of TREs. That is, there is a one-to-one logical association between a pool of Abis nibbles and a set of TREs. The basic and extra Abis nibbles in the pool are not shared among TREs in the same way. The different types of Abis nibbles in a pool are shared as follows: •

Extra Abis nibbles are shared at BTS level (e.g., among all TREs of the BTS)

•

Bonus basic Abis nibbles are also shared at BTS level

•

Basic Abis nibbles are shared at cell level (among all the TREs of the same sector in a shared cell). Note that in a cell shared over two BTS, only one BTS sector supports PS traffic.


3-33



....................................................................................................................................................................................................................................

To build Abis nibble pools, each basic Abis nibble is statically mapped on an Abis timeslot. There are two 64k Abis timeslots reserved per TRE. This is important for CS traffic because a TCH always uses the basic Abis nibble that was initially mapped on its timeslot. For the extra Abis nibbles, a number of 64k Extra timeslots (EXTS) are defined for each BTS. Abis Resource Manager

The Abis resource manager handles the pools of basic and extra Abis nibbles associated with a given BTS. There is one Abis resource manager per BTS. The manager acts upon requested received from a higher-level transmission resource manager at GCH level. The Abis resource manager is located in the MFS since the MFS must manage the Abis nibbles in order to manage pre-emption due to CS traffic. Because there is a manager for each BTS, the Abis resource manager for a given BTS is located on one unique GP in the MFS. Abis nibbles are allocated to a TRE using the GSL-RSL interfaces. Abis nibbles are identified in the BSS by a physical identifier. The Abis resource manager must be able to address an Abis nibble at both the BSC and BTS sides. A physical identifier for the nibble means that no BSC Abis nibble id-to-BTS Abis nibble id conversion is necessary. This avoids complexity and BSC load-related problems. Abis Nibble Pool Management

The Abis resource manager uses the following input messages to manage the Abis nibble pools: •

Cell State Response / Cell State Change messages (the contents of the two messages are the same)

•

Extra Abis Pool Configuration messages, indicating the list of extra Abis timeslots available for PS traffic in a BTS

•

RR Allocation Indication messages, indicating which radio timeslots are available for PS traffic (i.e., which radio timeslots whose basic Abis nibbles can be used / can no longer be used for PS traffic)

•

Cell Deletion messages.

Depending on the message and its contents, the Abis resource manager acts as described below. For a Cell State Change message: •

When a PS capable TRE is removed, the corresponding basic Abis nibbles are immediately removed from the Abis pool. The Abis resource manager triggers the release of the current GCHs of the TRE and the release of the GCHs currently using the basic Abis nibbles initially mapped to the TRE (if any). All the basic nibbles associated with the TRE are de-allocated from the TREs using them. The Abis and Ater nibbles of the concerned GCHs are then de-switched in the BSC.

•

When a PS capable TRE is added, the resource manager does nothing.

....................................................................................................................................................................................................................................

3-34




....................................................................................................................................................................................................................................

•

If the basic Abis nibble-to-timeslot mapping for a TRE has changed, the old basic Abis nibbles are immediately removed from the pool. The manager triggers the release of the current GCHs of the TRE and of the GCHs currently using the old basic Abis nibbles of the TRE (if any). The Abis and Ater nibbles of the impacted GCHs are then de-switched in the BSC.

•

If some basic Abis nibbles used for the BCCH or the static SDCCH are no longer present in the Cell State Change message, the corresponding basic Abis nibbles are immediately removed from the Abis pool. The corresponding GCH links (if any) are released.

•

If there are new basic Abis nibbles available for PS traffic due to BCCH / static SDCCH channels in the Cell State Change message, these basic nibbles are added to the Abis nibble pool.

Upon receipt of an Extra Abis Pool Configuration message, the resource manager: •

Deletes from the Abis pool any EXTSs indicated as removed from the list of available EXTSs. The corresponding GCHs are released and the Abis and Ater nibbles are then de-switched in the BSC.

•

Adds new EXTSs to the Abis pool. From that moment on, the new EXTSs are available to any M-EGCH in the BTS.

Upon receipt of an RR Allocation Indication message, the Abis resource manager: •

Pre-empts any basic Abis nibbles whose timeslots are no longer available for PS traffic. The corresponding GCHs (if any) are released and Abis-Ater de-switching is done in the BSC.

•

Adds any basic Abis nibbles whose timeslots are newly available for PS traffic to the Abis pool.

When a Cell Deletion message is received by the MFS, the Abis resource manager immediately removes all the basic nibbles of the cell (TREs BCCH, static SDCCH) from the pool. All the GCHs using these nibbles are released (but they can be used in another cell). Then Abis-Ater de-switching is done in the BSC.


3-35


Enhanced Transmission Resource Management

....................................................................................................................................................................................................................................

Enhanced Transmission Resource Management Overview

With the M-EGCH Statistical Multiplexing and the Dynamic Abis Allocation features, better management of transmission resources (Ater and Abis nibbles) is possible. This reduces the consumption and waste of transmission resources. A dedicated transmission resource manager operating at MFS / GP level is also added. This resource manager handles both Abis and Ater resources at the GCH level. The transmission resource manager is in charge of: •

Creating and removing the M-EGCH links

•

Selecting, adding, removing and redistributing GCHs over the M-EGCH links

•

Managing transmission resource pre-emptions

•

Managing Abis and / or Ater congestion states

•

Optionally, monitoring M-EGCH link use, according to the (M)CS of their supported TBFs (UL and DL).

Frequency Hopping Overview

Frequency hopping improves the bit error rate and therefore contributes to overall network quality. Frequency hopping, already provided for circuit-switched channels, is extended to the packet-switched channels for GPRS implementation. The BSS sends the hopping law when setting up a connection. All GPRS channels then use the same hopping law in a synchronized scheme. For more information about frequency hopping, refer to Chapter 5, “Call Set Up”.

....................................................................................................................................................................................................................................

3-36



PCM Link Sharing

....................................................................................................................................................................................................................................

PCM Link Sharing Overview

Resource allocation is made easier by the use of a shared 2048 kb/s PCM link. GPRS signaling and traffic channels can be multiplexed with circuit-switched traffic channels on this link between the MFS and the BSC. Traffic on the Ater Mux Interface between the MFS and the Transcoder is either processed by the MFS as GPRS traffic, or passed transparently through the cross-connect in the MFS to the BSC as circuit-switched traffic.

TBF Resource Re-allocation Overview

Resource re-allocation is enabled using the EN_RES_REALLOCATION parameter. The feature provides radio and transmission resources for a TBF following an uplink request received from the mobile station, or following one or more downlink LLC-PDUs received from the SGSN, when there is no established TBF for the mobile station. More than one TRX can be allocated to GPRS services in any given cell. Resource allocation must be prioritized, so priority is set on PDCH groups. The allocation is granted to the PDCH group with the highest priority. This avoids PDCH groups in a congested state and PDCH groups that are dual-rate capable. The requested throughput is served by the: •

Maximum number of slots allowed by the mobile station multislot class

•

GPRS service constraints (the operator gives the maximum number of allowed slots for one GPRS connection)

•

Network constraints (resource availability).

The allocation strategy consists of maximizing the allocated PDCH(s) use and, if necessary, requesting additional PDCH(s) from the BSC. EGPRS traffic has priority over GPRS traffic. For example, TRXs with high throughput are used for EGPRS traffic. Although GPRS throughput is optimized using TRXs with high throughput, this occurs only when there is no conflict with EGPRS traffic. The following table describes the four types of TBF re-allocations. This type of re-allocation...

Is used to...

T1

Maintain a TBF alive despite a pre-emption.


3-37


TBF Resource Re-allocation

....................................................................................................................................................................................................................................

This type of re-allocation...

Is used to...

T2

Re-allocate an ongoing TBF when establishing a concurrent TBF when:

T3

T4

•

A downlink TBF is established concurrent with an existing uplink TBF, which is allocated with the maximum number of timeslots supported in the direction of the bias, re-allocation cannot be given to the mobile station

•

An uplink TBF is established concurrent with a downlink TBF.

Offer better throughput to ongoing TBFs when: •

A TBF cannot be served with the maximum number of PDCHs it supports, because: – Of lack of resources at the time of the request – The EGPRS class is used to establish a GPRS TBF, where the GPRS mobile station class allows a greater number of allocated PDCHs with better PDCH allocation available to serve the TBF.

•

"Signaling traffic" becomes "data traffic"

•

An EGPRS TBF is served on a TRX which offers a higher throughput (i.e., a better TRX class). In this case, "Signaling traffic" becomes "data traffic", and an EGPRS TBF is served on a TRX which offers a higher throughput (i.e., a better TRX class).

Move an uplink GPRS TBF sharing one PDCH with a downlink EGPRS TBF onto PDCHs which do not support a downlink EGPRS TBF. When one PDCH is shared between an uplink GPRS TBF and a downlink EGPRS TBF, the downlink EGPRS TBF is limited to GMSK (i.e., MCS4). Consequently, after a T4 re-allocation the downlink EGPRS TBF is able to use 8-PSK (i.e., up to MCS9). T4 re-allocation is not used with dual transfer mode mobile stations.

....................................................................................................................................................................................................................................

3-38



Dynamic Allocation

....................................................................................................................................................................................................................................

Dynamic Allocation Overview

When an uplink TBF is established for a mobile station, the network provides to the mobile station the list of the uplink PDCHs assigned for that TBF and the list of the USF identifiers of this TBF. One unique USF is assigned per TBF per assigned PDCH. During the lifetime of the TBF, the mobile listens to the downlink PDCHs corresponding to its uplink assigned PDCHs. On one assigned PDCH, whenever the mobile station detects its USF (note that in this example, there is only one TBF established per mobile station per direction, i.e. that there is no "multiple TBF" feature), which means that it is allowed to transmit on the same uplink PDCH in the next Block Period.

Extended Dynamic Allocation Overview

The Extended Dynamic Allocation (EDA) is an extension of the basic Dynamic Allocation (E)GPRS MAC mode to allow higher throughput in uplink for type 1 mobile stations (supporting the feature) through the support of more than two radio transmission timeslots. With EDA mode, the mobile station detects an assigned USF value for any assigned uplink PDCH and allows the mobile station to transmit on that PDCH and all higher numbered assigned PDCHs. The mobile station does not need to monitor all the downlink PDCH corresponding to its uplink PDCH allocated, which allows the type 1 mobile station to support configurations with more uplink timeslots (and therefore with less downlink timeslots). The feature is mainly used only whenever the mobile station relies on its own resources.


3-39

GPRS in Alcatel-Lucent BSS Traffic Load Management


....................................................................................................................................................................................................................................

Traffic Load Management Overview of Traffic Load Management Overview

Traffic load conditions affect PDCH allocation, as described in “Congestion Control” (p. 3-41). A PDCH can have one of four possible states, as shown in the following table. State

Explanation

Empty

No established TBFs.

Active

At least one established TBF and the total number of established TBFs is smaller than a defined threshold (O&M parameter N_TBF_PER_SPDCH).

Busy

The number of established TBFs is greater than or equal to O&M parameter N_TBF_PER_SPDCH but smaller than the maximum allowed (O&M parameter MAX_UL/DL_TBF_SPDCH).

Full

The number of established TBFs is equal to the maximum set by O&M parameter MAX_UL/DL_TBF_SPDCH.

Smooth PDCH Traffic Adaption to Cell Load Variation Overview

To avoid wasting GPRS traffic resources when entering a high load situation (with the ability to allocate GPRS traffic on multiple TRXs, the gap between MAX_PDCH and MAX_PDCH_HIGH_LOAD can be much bigger than in release B6.2), the BSC evaluates the total (circuit and packet-switched) traffic per cell and indicates the number of PDCHs that can be granted for GPRS traffic to the MFS. The BSC notifies the MFS about any change in the number of available GPRS resources. Therefore, the GPRS traffic is constantly adapted to the actual traffic situation in the cell. The Load_EV_Period_GPRS parameter controls smooth PDCH traffic adaptation. It calculates the number of load samples (calculated every TCH_INFO_PERIOD) for the PDCH traffic adaptation load averaging algorithm.

....................................................................................................................................................................................................................................

3-40


GPRS in Alcatel-Lucent BSS Traffic Load Management

Congestion Control

....................................................................................................................................................................................................................................

Congestion Control Overview

Capacity on demand allows operators to both reserve a number of PDCH for GPRS traffic and reserve other PDCH for shared traffic, according to the real traffic load in the cell at any given moment. The actual GPRS traffic load is dynamically matched by allocating or de-allocating PDCH after negotiation between the MFS and the BSC. The BSC is the master in the negotiation process, which means if circuit-switched traffic is heavy in a cell, there is no guarantee a GPRS mobile station can establish a call. To ensure GPRS calls are possible at any time, the MIN_PDCH parameter can be set at the OMC-R to define the number of PDCH permanently allocated to GPRS in a cell. Using this parameter to set the minimum number of PDCH allocated to GPRS traffic also sets the maximum number of radio timeslots allocated to circuit-switched traffic. For GPRS calls, it is also necessary to get an Ater resource. The function "fast GPRS access" (at least one PDCH always established in a cell) fulfills this requirement.

M-EGCH Statistical Multiplexing Overview

M-EGCH Statistical Multiplexing provides a means of sharing Ater and Abis nibbles between the radio timeslots of a TRX. With this feature, transmission resources left available by a PDCH can be re-used by other PDCHs belonging to the same TRX. This avoids wasting transmission bandwidth on both the Ater and Abis interfaces. The feature reduces the amount of GCH resources used, especially on the Ater. It multiplexes the blocks of all the PDCHs of a TRX on a single transmission link, the M-EGCH (Multiplexed-EGCH) link. This link is established between the MFS and the BTS. M-EGCH links are defined per TRX (instead of as a single EGCH link per PDCH). This allows the (M)CS variations of the TBFs mapped on a TRX to compensate each other without requiring more transmission resources. With M-EGCH statistical multiplexing, in the downlink, the TBF is selected first and then the PDCH. For more information about the M-EGCH link, see “GCH Interface” (p. 3-16).


3-41

Contents About this document Purpose

xxiii xxiii ........................................................................................................................................................................................

Reason for reissue

xxiv xxiv ...................................................................................................................................................................

New in this release

xxiv xxiv ..................................................................................................................................................................

Intended audience

xxiv xxiv ....................................................................................................................................................................

Supported systems

xxv xxv ....................................................................................................................................................................

How to use this document Prerequisites

xxv xxv ................................................................................................................................................................................

Conventions used

xxv xxv ......................................................................................................................................................................

Related information

xxvi xxvi ...................................................................................................................................................................

Technical support

xxvi xxvi .....................................................................................................................................................................

xxvi xxvi ..............................................................................................................................................................................

How to comment

xxvi xxvi ......................................................................................................................................................................

Introduction to GSM Overview

1-1 1-1 ......................................................................................................................................................................................

GSM Background

1-1 1-1 .....................................................................................................................................................................

GSM Archi Architectu tecture re

1-3 1-3 .....................................................................................................................................................................

GSM Functions

2

xxvi xxvi ................................................................................................................................................................

Document support

How to order

1

xxv xxv ......................................................................................................................................................

1-8 1-8 ..........................................................................................................................................................................

Alcatel-Lucent BSS Overview

2-1 2-1 ......................................................................................................................................................................................

BSS Overview

2-1 2-1 ............................................................................................................................................................................


2-6 2-6 .......................................................................................................................................


iii

Contents ....................................................................................................................................................................................................................................

Packet Data Protocol Protocol Context Activation Data Transfer

3-47 ......................................................................................................................3-47

3-51 3-51 ............................................................................................................................................................................

Packet Data Protocol Context De-activation

3-61 ................................................................................................................3-61

GPRS Suspend

3-66 3-66 ........................................................................................................................................................................

GPRS Resume

3-68 3-68 .........................................................................................................................................................................

GPRS Detach

3-71 3-71 ...........................................................................................................................................................................

Location Services

Overview of Location Services Logical Logi cal Archi Architectu tecture re

3-75 3-75 .........................................................................................................................................

3-76 3-76 ..............................................................................................................................................................

LCS Positioning Methods

3-77 3-77 ...................................................................................................................................................

LCS Scenario in Circuit-Switched Domain Physical Implementation

3-79 ..................................................................................................................3-79

3-79 3-79 .....................................................................................................................................................

SMLC Functions ..................................................................................................................................................................... 3-80 3-80 BSS and Cell Configuration LCS O&M

3-81 3-81 ...............................................................................................................................................

3-81 3-81 .................................................................................................................................................................................

High Speed Data Service

HSDS Description

3-83 3-83 ..................................................................................................................................................................

GPRS CS3/CS4 and EGPRS Protocol ............................................................................................................................ 3-84 3-84 Transmission Transmiss ion Handling ......................................................................................................................................................... 3-87 3-87 Cell/GP Mapping Modification

3-89 3-89 .........................................................................................................................................

Gb over IP

Overview Gb over IP

4

3-90 3-90 ............................................................................................................................................................

Voice services over over Adaptive Multi-user channels on One Slot (V (VAMOS) AMOS) Overview

4-1 4-1 ......................................................................................................................................................................................

VAMOS

VAMOS Overview

4-2 4-2 ...................................................................................................................................................................

....................................................................................................................................................................................................................................

vi


Contents ....................................................................................................................................................................................................................................

Downlink

Orthogonal SubChannels Concept ...................................................................................................................................... 4-3 4-3 VAMOS Adaptive Symbol Constellation ......................................................................................................................... 4-4 4-4 Training Trainin g Sequences Used in VAMOS VAMOS VAMOS Operation in DTX Power Control in VAMOS VAMOS

4-5 ...............................................................................................................................4-5

4-6 4-6 .................................................................................................................................................. 4-7 4-7 .....................................................................................................................................................

Associated Control Channels

4-8 4-8 ...............................................................................................................................................

Uplink

Burst Structure and Training Sequence Codes Associated Control Channels

44-10 -10 ............................................................................................................4-10

4-10 4-10 .............................................................................................................................................

Reception of VAMOS SubChannels at the BTS

44-10 -10 .........................................................................................................4-10

Mobile Station Types Types for VAMOS

Overview of Mobile Station Types for VAMOS

44-11 -11 .........................................................................................................4-11

VAMOS Possible Multiplexing Combinations

Overview of VAMOS Possible Multiplexing Combinations

5

44-12 -12 .................................................................................4-12

Call Set Up Overview

5-1 5-1 ......................................................................................................................................................................................

Call Set Up

Overview of Call Set Up Call Types

5-3 5-3 ........................................................................................................................................................

5-3 5-3 ....................................................................................................................................................................................

Call Set Up Phases

5-4 5-4 ...................................................................................................................................................................

Mobile-Originated Call

Overview of Mobile-Originated Call

5-5 5-5 ................................................................................................................................

Radio and Link Establishment

5-5 5-5 .............................................................................................................................................

Authentication and Ciphering

5-15 5-15 ............................................................................................................................................

Normal Assignment

5-16 5-16 ...............................................................................................................................................................


vii

Contents ....................................................................................................................................................................................................................................

Mobile-Terminated Call

Overview of Mobile-Terminated Call

5-24 ............................................................................................................................. 5-24

Radio and Link Establishment

5-25 ........................................................................................................................................... 5-25

Authentication and Ciphering

5-26 5-26 ............................................................................................................................................

Normal Assignment

5-26 5-26 ...............................................................................................................................................................

Off Air Call Call Set Up

5-28 5-28 ................................................................................................................................................................

IMSI Atta Attach-De ch-Detach tach

5-28 5-28 ..............................................................................................................................................................

Paging

Overview of Paging Paging Control

5-29 5-29 ...............................................................................................................................................................

5-31 5-31 .........................................................................................................................................................................

Discontinuouss Reception Discontinuou

5-34 5-34 .....................................................................................................................................................

Congestion

Overview of Congestion

5-35 5-35 ......................................................................................................................................................

Queueing .................................................................................................................................................................................... 5-35 5-35 In-queue

5-36 5-36 .....................................................................................................................................................................................

Pre-emption

5-38 5-38 ..............................................................................................................................................................................

Classmark Handling

Overview of Classmark Handling Classmark IE

5-40 5-40 ....................................................................................................................................

5-41 5-41 ............................................................................................................................................................................

Classmark Updating

5-43 5-43 ..............................................................................................................................................................

Location Updating with Classmark Procedure

55-44 -44 ............................................................................................................5-44

Authentication

Overview of Authenticatio Authentication n IMSI/TMSI

5-47 5-47 ...............................................................................................................................................

5-47 5-47 ...............................................................................................................................................................................

Authentication Procedure

5-49 5-49 ....................................................................................................................................................

....................................................................................................................................................................................................................................

viii


Contents ....................................................................................................................................................................................................................................

Ciphering

Overview of Ciphering

5-51 5-51 .........................................................................................................................................................

Mobile Station Ciphering Capability BSS Ciphering Capability

5-52 ..............................................................................................................................5-52

5-52 5-52 ...................................................................................................................................................

Ciphering Keys ........................................................................................................................................................................ 5-53 5-53 Ciphering Process ................................................................................................................................................................... 5-54 5-54 Ciphering in DTM Mode

5-57 5-57 .....................................................................................................................................................

Tandem Free Operation

Overview of Tandem Free Operation TFO Process

5-58 ..............................................................................................................................5-58

5-59 5-59 .............................................................................................................................................................................

TFO Functional Architecture

5-60 5-60 .............................................................................................................................................

TFO Optimization and Management ............................................................................................................................... 5-62 5-62

6

Call Handling Overview

6-1 6-1 ......................................................................................................................................................................................

Overview of Call Handling

Overview

6-4 6-4 ......................................................................................................................................................................................

In-Call Modification

Overview of In-Call Modification In-Call Modification Procedure

6-5 6-5 ......................................................................................................................................

6-6 6-6 ...........................................................................................................................................

Circuit-Switched Group 3 Fax Data Rate Change Error Handling

66-7 -7 ........................................................................................................6-7

6-8 6-8 ...........................................................................................................................................................................

Frequency Hopping

Overview of Frequency Hopping Baseband Frequency Hopping

6-9 ........................................................................................................................................ 6-9

6-10 6-10 ...........................................................................................................................................

Synthesized Frequency Hopping

6-12 6-12 ......................................................................................................................................


ix

Contents ....................................................................................................................................................................................................................................

Speech Transmission

Overview of Speech Transmission Continuous Transmission

6-13 6-13 ....................................................................................................................................................

Discontinuous Transmission Voice Activity Detection

6-13 ................................................................................................................................... 6-13

6-13 6-13 ..............................................................................................................................................

6-14 6-14 ......................................................................................................................................................

BSS Discontinuous Transmission Towards Mobile Station Mobile Station Discontinuous Transmission Towards BSS

-15 ...................................................................................66-15

-16 ...................................................................................66-16

Radio Power Control

Overview of Radio Power Control BTS Radio Power Control

6-19 6-19 ..................................................................................................................................

6-19 6-19 ..................................................................................................................................................

Mobile Station Radio Power Control Radio Link Measurements

6-20 ..............................................................................................................................6-20

6-20 6-20 ..................................................................................................................................................

Power Control Decision and Handover Change Power Levels

6-21 ..........................................................................................................................6-21

6-23 6-23 ...........................................................................................................................................................

Packet Downlink Power Control

6-25 6-25 ......................................................................................................................................

Handover

Overview of Handover

6-26 6-26 .........................................................................................................................................................

Principal Handover Types

6-27 6-27 ...................................................................................................................................................

Radio Measurements

6-29 6-29 .............................................................................................................................................................

Handover Detection

6-31 6-31 ...............................................................................................................................................................

Handover Detection Overview

6-31 6-31 ..........................................................................................................................................

Handover Detection Quality and Level Handover

-32 .....................................................................................................66-32

Handover Detection Level Intercell Handover ............................................................................................................ 6-34 6-34 Handover Detection Quality Intercell Handover

-34 ........................................................................................................66-34

Handover Detection Quality Intracell Handover

-34 ........................................................................................................66-34

Handover Detection Better Zone Handover

6-35 .................................................................................................................6-35

Handover Detection Better Cell Handover

6-36 ...................................................................................................................6-36

....................................................................................................................................................................................................................................

x


Contents ....................................................................................................................................................................................................................................

Handover Detection Distance Handover

6-38 .......................................................................................................................6-38

Handover Detection Mobile Velocity Dependent Handover Handover Detection Multiband Handover Target Cell Evaluation

-40 ..................................................................................66-40

6-41 ....................................................................................................................6-41

6-42 6-42 ..........................................................................................................................................................

Synchronous and Asynchronous Handover Circuit-Switched Telecom Handovers

6-45 ..................................................................................................................6-45

6-49 ............................................................................................................................6-49

Overload Control

Overview of Overload Control

6-51 6-51 ..........................................................................................................................................

BTS Overload

6-51 6-51 ..........................................................................................................................................................................

BSC Overload

6-52 6-52 ..........................................................................................................................................................................

Call Re-establishment by Mobile Station

Overview of Call Re-establishment by Mobile Station

6-54 ............................................................................................ 6-54

User Prioritized Action Based on SIM (SIM Card Access Control)

Overview of User Prioritized Action Based on SIM (SIM Card Access Control) ......................................... 6-55 6-55 Interference Reduction

Interference Reduction Using IRC & EIRC

7

6-58 .................................................................................................................6-58

Call Release Overview

7-1 7-1 ......................................................................................................................................................................................

Call Release

Overview of Call Release

7-3 7-3 ......................................................................................................................................................

Call Release Procedures in Normal Service

Overview of Call Release Procedures in Normal Service

-5 .........................................................................................77-5

Normal Release .......................................................................................................................................................................... 7-6 7-6 Calls Terminated Following a Channel Change

-15 ..........................................................................................................77-15

Call Release - Special Cases

Overview of Call Release - Special Cases

7-17 ....................................................................................................................7-17


xi

Contents ....................................................................................................................................................................................................................................

Call Release Following Reset

7-17 7-17 ............................................................................................................................................

BSC-Initiated Release ........................................................................................................................................................... 7-20 7-20 BSC-Initiated SCCP Release BTS-Initiated Call Release

7-22 7-22 .............................................................................................................................................

7-23 7-23 .................................................................................................................................................

Mobile Station-Initiated Call Release

7-25 .............................................................................................................................7-25

Remote Transcoder Alarms ................................................................................................................................................. 7-27 7-27 Preserve Call Feature

Overview of Preserve Call Feature Normal Release

7-29 7-29 .......................................................................................................................................................................

Abnormal Release

8

7-29 7-29 ..................................................................................................................................

7-30 7-30 ..................................................................................................................................................................

Handling User Traffic Across the Alcatel-Lucent BSS Overview

8-1 8-1 ......................................................................................................................................................................................

User Traffic Across the Alcatel-Lucent BSS

Overview of Handling User Traffic Across the Alcatel-Lucent BSS

8-3 ..................................................................... 8-3

Speech

Overview of Speech Analog

8-4 8-4 .................................................................................................................................................................

8-5 8-5 ...........................................................................................................................................................................................

Interleaving and Forward Error Correction Speech Data Bursts Digital Speech

8-6 8-6 ..................................................................................................................................................................

8-6 8-6 ............................................................................................................................................................................

Digital 64 kbit/s A-law Encoded Speech Enhanced Full-Rate Half-Rate

8-5 .....................................................................................................................8-5

8-7 .......................................................................................................................... 8-7

8-8 8-8 ..................................................................................................................................................................

8-9 8-9 ......................................................................................................................................................................................

Adaptive Multiple Rate

8-10 8-10 ........................................................................................................................................................

Channel Mode Adaptation

8-14 8-14 ..................................................................................................................................................

VGCS .......................................................................................................................................................................................... 8-14 8-14

....................................................................................................................................................................................................................................

xii


Contents ....................................................................................................................................................................................................................................

Circuit-Switched Data Modes

Overview of Circuit-Switched Data Modes Transparent Mode

8-16 .................................................................................................................8-16

8-17 8-17 ..................................................................................................................................................................

Non-Transparent Mode

8-18 8-18 ........................................................................................................................................................

Short Message Service - Cell Broadcast

Overview of Short Message Service - Cell Broadcast

-20 ..............................................................................................88-20

SMS-CB Operation ................................................................................................................................................................ 8-21 8-21 Phase 2+ Enhancements ....................................................................................................................................................... 8-21 8-21 Support of Localized Service Area

Overview of Support of Localized Service Area

-22 ........................................................................................................88-22

PLMN Interworking

Overview of PLMN Interworking

9

8-23 8-23 ....................................................................................................................................

Cell Environments Overview

9-1 9-1 ......................................................................................................................................................................................

Cell Environments

Overview of Cell Environments

9-3 9-3 ..........................................................................................................................................

Rural and Coastal Coverage .................................................................................................................................................. 9-5 9-5 Urban Coverage

9-5 9-5 .........................................................................................................................................................................

Concentric Cell

Overview of Concentric Cell

9-6 9-6 ................................................................................................................................................

Sectored Site

Overview of Sectored Site

9-7 9-7 .....................................................................................................................................................

Extended Cell

Overview of Extended Cell

9-9 9-9 ...................................................................................................................................................

Standard Extended Cell

9-10 9-10 ........................................................................................................................................................

Enlarged Extended Cell

9-11 9-11 ........................................................................................................................................................


xiii

Contents ....................................................................................................................................................................................................................................

PS in Extended Cell

9-11 9-11 ...............................................................................................................................................................

Umbrella Cell

Overview of Umbrella Cell Mini Cell

9-12 9-12 ................................................................................................................................................

9-12 9-12 ....................................................................................................................................................................................

Microcell .................................................................................................................................................................................... 9-13 9-13 Indoor Cell

9-16 9-16 ................................................................................................................................................................................

Cell Shared by Two BTS

Overview of Cell Shared by Two BTS

9-18 ...........................................................................................................................9-18

Logical Cell

Overview of Logical Cell

9-19 9-19 ....................................................................................................................................................

Unbalancing TRX Output Power per BTS Sector

Overview of Unbalancing TRX Output Power per BTS Sector

9-20 ...........................................................................9-20

TRX Dynamic Power Saving

Overview of TRX Dynamic Power Saving

10

9-21 ..................................................................................................................9-21

Operations & Maintenance Overview

10-1 10-1 ...................................................................................................................................................................................

Operations and Maintenance

Overview of Operations and Maintenance Subsystem O&M Functions System O&M Functions

10-3 .................................................................................................................... 10-3

10-3 10-3 ...............................................................................................................................................

10-4 10-4 ......................................................................................................................................................

O&M Control - Subsystems

Overview of O&M Control - Subsystems LMTs and IMT

10-6 10-6 ........................................................................................................................................................................

OML Auto-Detection Managed Objects Security Blocks

10-6 .....................................................................................................................10-6

10-7 10-7 ............................................................................................................................................................

10-7 10-7 .................................................................................................................................................................... 10-8 10-8 .......................................................................................................................................................................

....................................................................................................................................................................................................................................

xiv


Contents ....................................................................................................................................................................................................................................

O&M Control via OMC-R

Overview of O&M Control via OMC-R ........................................................................................................................ 10-9 10-9 Multiple Human-Machine Interface ACO

10-9 10-9 ................................................................................................................................

10-11 10-11 ..........................................................................................................................................................................................

Connection from BSC to OMC-R Electronic Documentation

10-13 10-13 .................................................................................................................................

10-15 10-15 ................................................................................................................................................

Configuration Management

Overview of Configuration Management Hardware Configuration Logical Configuration

10-17 10-17 ....................................................................................................................................................

10-17 10-17 ........................................................................................................................................................

Default Parameter Customization Software Configuration Auto-Identification

10-16 ...................................................................................................................10-16

10-18 10-18 ..................................................................................................................................

10-18 10-18 .....................................................................................................................................................

10-19 10-19 ..............................................................................................................................................................

OML Auto-Detection

10-20 10-20 ..........................................................................................................................................................

Network Element Provisioning

10-21 ....................................................................................................................................... 10-21

Fault Management - Alarms

Overview of Fault Management - Alarms Alarm Generation Alarm Functions

10-23 ..................................................................................................................10-23

10-24 10-24 ................................................................................................................................................................ 10-25 10-25 ...................................................................................................................................................................

BSC Alarms

10-27 10-27 ...........................................................................................................................................................................

BTS Alarms

10-31 10-31 ............................................................................................................................................................................

Alarms Detected by the TSC MFS Alarms

10-32 10-32 ...........................................................................................................................................

10-33 10-33 ...........................................................................................................................................................................

Recovery Example: Carrier Unit Failures with BCCH Automatic Power-Down BSC Alerter

0-34 ..........................................................................................110-34

10-37 10-37 ....................................................................................................................................................

10-38 10-38 ............................................................................................................................................................................


xv

List of tables 1-1

Basic Teleservices

1-9 1-9 .....................................................................................................................................................

1-2

GSM Channel Characteristics

1-3

Control Channel Types

2-1


2-2

UTRAN/E-UTRAN FDD/TDD Supported Combinations

3-1

Network Operation Modes

4-1

TSC Set 1 & 2

5-1

Cell List Identifier and Paging Performed

5-31 5-31 .....................................................................................................

5-2

Cell List Identifier and Paging Performed

5-32 5-32 .....................................................................................................

6-1

Operator Discontinuous Transmission Options

6-2

Mobile Station Maximum and Minimum Power Ranges

8-1

Software Version versus Hardware Board/Feature

8-2

Circuit-Switched Data Rate Conversions Across the Air Interface

1-12 1-12 ............................................................................................................................

1-13 1-13 .......................................................................................................................................... 2-44 2-44 ........................................................................................................................... ...................................................................... 2-58

3-25 3-25 ..................................................................................................................................

4-5 4-5 .............................................................................................................................................................

6-16 ........................................................................................... 6-16 6-24 ......................................................................... 6-24

8-11 ..................................................................................... 8-11 ...................................................... 8-18


xvii

List of tables ....................................................................................................................................................................................................................................

....................................................................................................................................................................................................................................

xviii


List of figures 1-1

Base Station Subsystem

1-7 1-7 ..........................................................................................................................................

2-1

Synchronous Transport Mode level 1 (STM1)

2-2

Logical Position of External Components Associated with BSS

2-3

Location Updating

2-21 2-21 ..................................................................................................................................................

2-4

Location Updating

2-23 2-23 ..................................................................................................................................................

2-5

Timeslot 4 of a TDMA Frame Supporting Access Grant Channels

2-6

TMN System Hierarchy

3-1

Model LLC Packet Data Unit used in GPRS

3-2

The Alcatel-Lucent GPRS Solution in the PLMN

3-3

Mobile Station-Originating Packet Data Protocol Context Activation

3-4

GGSN-Originating Packet Data Protocol Context Activation

3-5

Mobile-Originating Packet Data Protocol Context De-activation

3-6

Network-Originating Packet Data Protocol Context De-activation Processes

4-1

OSC baseband transmitter

4-2

VAMOS baseband transmitter

4-3

Power control in VAMOS

4-4

FACCH soft stealing for two users sharing the same radio resource: TCH for both users A and B, FACCH for user B, FACCH for user A. ......................................................................................................... 4-9 4-9

4-5

VAMOS Multiplexing Combinations per timeslot

5-1

Radio and Link Establishment for Mobile-Originated Call

5-2

Connection for Mobile-Originated Call

5-3

Channel Request

5-4

Radio and Link Establishment for Mobile-Terminated Call

5-5

CCCH with Three Blocks Reserved for AGCH

2-5 2-5 ............................................................................................... .......................................................... 2-17

...................................................... 2-40

2-49 2-49 ........................................................................................................................................ 3-6 3-6 .................................................................................................. 3-7 ......................................................................................... 3-7 ............................................... 3-47

................................................................ 3-49 ........................................................ 3-61

3-64 ................................. 3-64

4-3 4-3 ...................................................................................................................................... 4-4 4-4 ..............................................................................................................................

4-8 4-8 .......................................................................................................................................

4-13 ..................................................................................... 4-13 ....................................................................... 5-7

5-13 5-13 ..........................................................................................................

5-18 5-18 ...................................................................................................................................................... ................................................................... 5-24

5-29 ........................................................................................... 5-29


xix

List of figures ....................................................................................................................................................................................................................................

5-6

Four TDMA Frame Cycles Providing 24 Paging Sub-channels

............................................................ 5-30

5-7

Location Update with Mobile Station Sending Location Area Identity of Previous VLR ........... 5-48 5-48

5-8

Example of TFO Establishment

6-1

Different Forms of Discontinuous Transmission

6-2

Power Output Balancing Based on Received Quality and Signal Levels

.......................................... 6-22

6-3

Power Output Balancing Based on Received Quality and Signal Levels

.......................................... 6-23

6-4

Umbrella Cell Load in Mobile Velocity Dependent Handover

6-5

Example of the New Round Robin Algorithm Applied for an ACC Configuration

7-1

Mobile Station Disconnecting a Call

7-2

Normal Call Release

7-3

Initiation of Normal Release by MSC

7-4

BSC/BTS/Mobile Station Interactions in Normal Call Release

7-5

Normal Release Final Steps

7-6

Call Release Following Reset

7-7

BSC-initiated Call Release Toward the MSC

7-8

BTS-initiated Call Release following LAPD Failure

7-9

Call Release due to Mobile Station-Initiated Radio Link Failure

7-10

Call Release Due to Communication Failure Detected by Transcoder

8-1

Encoded Speech Transmission Across the BSS with 9120 BSC

8-2

Multiplexed Ater Interface

8-3

Data Transmission Across the BSS

9-1

Example: Cell Configurations

9-2

Sectored Site Configuration

9-3

Example of Extended Cell Topology

9-4

Umbrella Cell with Mini Cells

9-5

Indoor Cell Example Network Hierarchy with Three Layers and Two Bands ................................. 9-17 9-17

10-1

Multiple HMI Access to OMC-Rs

5-59 5-59 ......................................................................................................................... 6-18 ......................................................................................... 6-18

.............................................................. 6-41

6-56 ....................... 6-56

7-6 7-6 ..................................................................................................................

7-8 7-8 ................................................................................................................................................. 7-9 7-9 ................................................................................................................ ............................................................ 7-12

7-13 7-13 ................................................................................................................................ 7-19 7-19 ............................................................................................................................. 7-21 7-21 ............................................................................................... 7-24 ................................................................................ 7-24 ......................................................... 7-26 ............................................... 7-28

............................................................. 8-4

8-7 8-7 ..................................................................................................................................... 8-16 8-16 ..................................................................................................................

9-4 9-4 ...............................................................................................................................

9-8 9-8 ................................................................................................................................... 9-9 9-9 .................................................................................................................

9-13 9-13 ...........................................................................................................................

10-10 10-10 ..................................................................................................................

....................................................................................................................................................................................................................................

xx


List of figures ....................................................................................................................................................................................................................................

10-2

ACO Links

10-12 10-12 ..............................................................................................................................................................

10-3

X.25 Without Redundancy

10-4

X.25 With Redundancy

10-5

RSL Correlation on the Abis Interface

10-6

Example Alarm Report

10-7

Example: Loss of Carrier Unit Holding BCCH.

10-8

RMS OMC-R Implementation.

10-43 10-43 .......................................................................................................................

10-9

RMSI OMC-R Implementation

10-45 10-45 .......................................................................................................................

10-13 10-13 ................................................................................................................................

10-14 10-14 ...................................................................................................................................... 10-28 10-28 ..........................................................................................................

10-30 10-30 ....................................................................................................................................... 10-36 ....................................................................................... 10-36


xxi

List of figures ....................................................................................................................................................................................................................................

....................................................................................................................................................................................................................................

xxii


About this document About this document

Purpose

This document provides a detailed overview of the Alcatel-Lucent Base Station Subsystem (BSS) and its functions and features, as well as an introduction to GSM operation and (E)GPRS. The first part of the document provides an overview of GSM functions and architecture, as well as a high level introduction to: •

The principle role and tasks of the Alcatel-Lucent BSS

•

Network organization, functions and network management

•

General BSS operations and maintenance (O&M).

The document then provides more specific technical information about: •

GPRS in the Alcatel-Lucent BSS This section provides an overview of GPRS functionality and processes as applied within the Alcatel-Lucent BSS.

•

Call set up, handling and release These sections provide detailed information about how the three major stages of call transmission and management are implemented in the Alcatel-Lucent BSS. Specific sections focus on how user traffic is handled across the BSS and how different cell environments impact call handling.

•

Operations and Maintenance (O&M). These sections describe the local and distributed O&M functions as they are applied in the Alcatel-Lucent BSS.

Note that some of the functions and features may not be available on the system installed at your location. The following convention applies for a 9125 TC equipped with a TC STM1 - IP subrack: •

TC STM1 interface board is also referred as TCIF

•

TC STM1 IP interface board is also referred as TCIFI.

................................................................................................................................................................................................................................... Alcatel-Lucent BSS 9YZ-03803-1802-TQZZA B12 Issue 4 October 2012

xxiii

About this document ....................................................................................................................................................................................................................................

Reason for reissue Issue number

Reason for reissue

4

Section “Radio Measurements Statistics Improved” (p. 10-43) was updated.

3

The following sections were updated:

2

•

Information about IRC & Enhanced IRC has been added in “Interference Reduction” (p. 6-58) .

•

Information about Flexible RMSI Report Content has been added in “Radio Measurements Statistics Improved” (p. 10-43)

•

Information about Packet Downlink Power Control and Reduction of Transmitted PDDCB has been added in “Radio Power Control” (p. 6-19)

Improvements performed in

1

•

“RMSI in OMC-R” (p. 10-43).

•

“Alcatel-Lucent Radio Solutions” (p. 2-2)

•

“Base Transceiver Station” (p. 2-8)

First official release of the document for B12 Release.

New in this release

This section contains information about changes to the current document. New features

IRC & Enhanced IRC Packet Downlink Power Control Reduction of Transmitted PDDCB Other changes

None. Intended audience

This document is for people requiring an in-depth understanding of Alcatel-Lucent BSS functions: •

Network decision makers who require an understanding of the underlying functions of the system

....................................................................................................................................................................................................................................

xxiv



Including:

•

–

Network planners

–

Technical design staff

–

Trainers.

Operations and support staff who need to know how the system operates in normal conditions Including: –

Operators

–

Support engineers

–

Maintenance staff

–

Client Help Desk personnel.

Supported systems

This document applies to Release B12 of the BSS. This document contains IP transport in the BSS related information. This feature is available commercially from Release B12. How to use this document

No specific recommendation applies regarding the way readers should read this document. Prerequisites

You must have a good understanding of: •

BSS

•

GSM

• GPRS •

Mobile telecommunications

•

Network Management concepts and terminology.

Conventions used

This section gives information on conventions. Vocabulary conventions

None.


xxv


Typographical conventions

The following typographical convention is used in this document: Appearance

Description

Italicized text

Emphasized information.

graphical user interface text

Text that is displayed in a graphical user interface or in a hardware label.

Document reference, reference number

Related document that is referenced in the document.

Related information

None. Document support

For support in using this or any other Alcatel-Lucent document, contact Alcatel-Lucent at one of the following telephone numbers: •

1-888-582-3688 (for the United States)

•

1-317-377-8618 (for all other countries)

Technical support

For technical support, contact your local Alcatel-Lucent customer support team. See the Alcatel-Lucent Support web site (http://www.alcatel-lucent.com/support/) for contact information. How to order

To order Alcatel-Lucent documents, contact your local sales representative or use Online Customer Support (OLCS) (http://support.alcatel-lucent.com) How to comment

To comment on this document, go to the Online Comment Form (http://infodoc.alcatellucent.com/comments/) or e-mail your comments to the Comments Hotline ([email protected]).

....................................................................................................................................................................................................................................

xxvi


1

1 Introduction to GSM

Overview Purpose

This section reviews basic mobile communications concepts and provides an overview of GSM architecture and functions, including its evolution to (E)GPRS. Contents GSM Background

1-1

GSM Architecture

1-3

GSM Functions

1-8

GSM Background Overview

The Group Special Mobile was originally part of the European Conference of Posts and Telecommunications (CEPT) group. This organization was responsible for developing the first mobile telecommunication standards. It produced recommendations for mobile services, radio transmission, network architecture and interfaces between subsystems. The resulting cellular radio telephone system is known as the Global System for Mobile Communications, or GSM. GSM standardization was later taken over by the global European standards organization, the ETSI, and in 1998 a collaboration agreement was established between a number of telecommunications standards bodies, resulting in the 3rd Generation Partnership Project Agreement (3GPP). 3GPP is responsible for defining recommendations for the advanced use of cellular radio telephone systems. The recommendations are defined by technological generations.


1-1

Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

GSM Architecture Overview

The GSM architecture is a functional structure defined to ensure compatibility between the different subsystems, their components and the communication interfaces. The definition is based on the GSM recommendations. Standard GSM PLMN

A public land mobile network (PLMN) is a network that is established and operated by an administration or by a recognized operating agency for the specific purpose of providing land mobile telecommunications services to the public. Access to PLMN services is achieved by means of an air interface involving radio communications between mobile phones or other wireless enabled user equipment and land based radio transmitters or radio base stations PLMNs interconnect with other PLMNs and public switched telephone networks (PSTNs) for telephone communications or with internet service providers for data and internet access. The standard GSM PLMN, shown in the figure below, consists of: •

Mobile stations, to transmit and receive calls

•

At least one BSS, to act as the radio part that connects the mobile station to the switching part of the PLMN

•

The Network Subsystem (NSS), to manage switching, interconnection and subscriber data.


1-3

Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

GSM/(E)GPRS PLMN

Enhanced GPRS (EGPRS) is a digital mobile phone technology that allows increased data transmission rates and improved data transmission reliability.

....................................................................................................................................................................................................................................

1-4


Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

A GSM/(E)GPRS PLMN, shown in the figure below, consists of: •

Mobile stations, to transmit and receive calls

•

At least one BSS, to act as the radio part that connects the mobile station to the switching part of the PLMN

•

At least one MFS (see “Multi-BSS Fast Packet Server” (p. 2-13)).


1-5

Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

Legend:

MFS


Mobile Stations

Mobile stations (MS) are the only items of mobile telecommunications equipment the subscriber physically uses. They can be vehicle mounted or portable kits, but the most popular models are hand-held stations. Mobile stations provide generic radio and processing functions, allowing subscribers to access the mobile network via a radio interface called the Air Interface. Modern MS and their associated service providers propose many features, including Short Message Services (SMS), Multimedia Services (MMS), the ability to transfer data to and from computers and faxes, television and radio streaming, and the possibility of creating and manipulating photos and video imaging. For more detailed information about MS, refer to “Mobile Stations” (p. 2-19). Base Station Subsystem

The Base Station Subsystem (BSS) is the section of a traditional cellular telephone network which is responsible for handling traffic and signaling between a mobile phone and the NSS. The BSS carries out transcoding of speech channels, allocation of radio channels to mobile phones, paging, quality management of transmission and reception over the Air interface and many other tasks related to the radio network. In summary, the BSS connects the mobile stations to the switching part of the GSM PLMN, as shown in the figure below: Figure 1-1 Base Station Subsystem

....................................................................................................................................................................................................................................

1-6


Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

Legend:

MFS


A BSS comprises: •

At least one Base Transceiver Station (BTS), which provides the radio links between the mobile stations and the Base Station Controller (BSC)

•

A BSC, which controls several BTSs

•

A Transcoder (TC), located between the BSC and the NSS.

The BSS can include additional transmission equipment to perform multiplexing and monitoring functions. With (E)GPRS data traffic, the BSS also includes a Multi-BSS Fast Packet Server (MFS) to manage data packets and perform Location Services (LCS) through Serving Mobile Location Center (SMLC) functions within the MFS. For detailed information about the Alcatel-Lucent BSS, refer to “BSS Overview” (p. 2-1). Network Subsystem

The main role of the NSS is to manage communication within the PLMN and with the public telephone network. The NSS manages the subscriber administration databases. It is sometimes referred to as the Core Network (CN). For more information, refer to “Network Subsystem” (p. 2-17). BSS Telecommunications Layers

The telecommunications functions of a GSM network are split into two basic layers: •

•

The Application layer, split into sub-layers These sub-layers control: –

Call management

–

Mobility management

–

Radio resource management.

The Transmission layers, which provide transmission to various components.

For a detailed description of the BSS telecommunications layers, refer to “Telecommunications Layers in the Alcatel-Lucent BSS” (p. 2-30).


1-7

Introduction to GSM

GSM Architecture

....................................................................................................................................................................................................................................

Network Management

In GSM, the PLMN is managed according to a network management concept referred to as the Telecommunication Management Network (TMN). The TMN defines a set of network management functions according to the ISO systems management rules. For more information, see “Telecommunications Management Network” (p. 2-48). Operations and Maintenance (O&M) describes the set of actions that monitor, control, and record how the system is functioning. O&M activities are divided into three functional groups: •

Configuration Management

•

Fault Management

•

Performance Management.

The exact implementation of these functional groups for network management is not strictly defined within GSM. Therefore, Alcatel-Lucent has developed its O&M concept to ensure high performance. For further information on O&M, refer to: •

Chapter 10, “Operations & Maintenance”

•

Alcatel-Lucent GSM 2G - OAM - Operations & Maintenance Principles

•

Alcatel-Lucent 9153 Operation & Maintenance Center Radio - Getting Started.

GSM Functions Overview

The primary function of a GSM network is to provide a consistent mobile telecommunication service. To do so, GSM supports a number of standardized services, some of which guarantee basic telephony services and others which provide an extra level of service for the user and service provider. Mobile Network Services

Network operators can implement three types of mobile network services: • Teleservices •

Bearer services

•

Supplementary services.

....................................................................................................................................................................................................................................

1-8


Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

Teleservices Table 1-1

Basic Teleservices

Service

Description

Telephony

GSM supports telephony with the ability to send or receive calls anywhere in the world where there is GSM or fixed network coverage.

Emergency call

GSM allows calls to be routed to an emergency service. Emergency calls have priority. If there are insufficient radio resources, the call request is queued at the highest priority.

Data Calls

GSM supports the transmission of a wide range of data and offers a variety of transmission types. (E)GPRS increases the throughput of data traffic.

Fax

High speed telefax messages can be sent to or received from a standard fax machine anywhere in the world.

Videotex

GSM supports the transmission of videotex information such as is used in the Minitel.

SMS

SMS allows the transmission of messages containing up to 160 alphanumeric characters to be sent to a subscriber. The SMS center interfaces with other network services such as paging, message handling and voice messaging.

MMS

MMS allows the transmission of messages containing test, voice and images to be sent to a subscriber. The MMS center interfaces with other network services such as paging, message handling and voice messaging.

Cell Broadcast

Cell broadcast is a short message service which allows short messages to be sent to all phones in a geographical area.

Bearer Services

Bearer services provide basic transmission functions. GSM uses a variety of bearer services to provide the different speeds and communications types required to run a range of service applications, including data transmission. Supplementary Services

In addition to the teleservices provided by a mobile network, the network supports the following supplementary services that are provided by the NSS, with input from other elements. These are administered by the Network Operator and offered to the mobile subscriber as options: •

Call forwarding (unconditional, mobile subscriber busy, no reply, mobile not reachable)

•

Call barring (outgoing, outgoing international, outgoing international except to home country, incoming, incoming when roaming abroad)

•

Call waiting, call hold, and multi-party service such as the Voice Group Call Service (VGCS)


1-9

Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

•

Call prioritization, using features such as Enhanced Multi Level Priority and Pre-emption (eMLPP)

•

Billing advice.

GSM defines a comprehensive set of recommendations concerning the management and implementation of these services, in conjunction with 3GPP and other standardization groups. Call Management

Communication to or from a mobile station must be: • Initiated • Authenticated • Established • Maintained • Analyzed • Terminated. For more information about call management, refer to: •

“Alcatel-Lucent BSS Functions” (p. 2-25)

•

Chapter 5, “Call Set Up”

•

Chapter 6, “Call Handling”

•

Chapter 7, “Call Release”.

Location Services (LCS)

LCS are optional, end-user services that provide the geographical location (longitude, latitude, and, optionally, altitude) of mobile stations. For more information, refer to “Location Services” (p. 3-75). Location Updating

Location updating allows the network to know the location of a mobile station at any given time. It lets the mobile station identify a change in cell location and initiate automatic updating procedures. For more information, refer to “Location Updating” (p. 2-21). Network Security

This section describes the security functions available to the Network Operator to minimize the risk of fraudulent use of the network.

....................................................................................................................................................................................................................................

1-10


Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

Subscriber Identity Confidentiality

Each subscriber has a personal Subscriber Identity Module (SIM) card. The SIM is part of a removable smart Integrated Circuit Card (ICC) which stores all the information a subscriber requires to use a GSM mobile telephone, and which can be transferred to any mobile cellular telephony device such as mobile computers and mobile phones. The SIM is protected against unauthorized access by a PIN code. SIM cards conform to internationally recognized standards and securely store the service-subscriber key, the International Mobile Subscriber Identity (IMSI), which is used to identify a subscriber in the network, to provide security and protection against misuse, and to acquire other details of the mobile in the HLR or in the VLR. The network must identify the mobile subscriber at the beginning of each transaction between a mobile station and the network. The mobile station sends its related IMSI, stored on the SIM, to the network. The IMSI must be protected when sent over the Air Interface. Therefore, the VLR assigns the IMSI a TMSI. The TMSI is ciphered when transmitted to the mobile station, where it is stored. For more information, refer to “Authentication and Ciphering” (p. 5-15). Keys and Triplets

A secret identification key is associated with each IMSI. One copy of this data is stored on the SIM. A second copy of the data is stored in the AUC, which verifies security data for each subscriber attached to it. For more information, refer to “Authentication and Ciphering” (p. 5-15). Authentication

For authentication purposes, the VLR chooses a triplet and sends the value of the random number to the mobile station. The mobile station calculates the value of the signed response and returns it to the VLR, where it is compared with the value in the selected triplet. If the signed response value is the same, then the mobile station is ready for use. If not, no calls are permitted for the mobile station. A mobile station which is unknown to the PLMN and which enters a VLR's territory is authenticated if there is a roaming agreement with the mobile station's home network. If not, no calls are permitted for the mobile station. For more information, refer to “Authentication and Ciphering” (p. 5-15). Channels

The following table shows the used frequency channels between the mobile station and the BTS.


1-11

Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

Table 1-3

Control Channel Types

This control channel...

Is used to...

Slow Associated Control CHannel (SACCH)

Control and supervise the associated TCHs.

Fast Associated Control CHannel (FACCH)

Handle irregular control requirements, for example, handovers.

Dedicated Control CHannel (DCCH)

Manage location updating, authentication, call set up, and SMS.

Broadcast Control CHannel (BCCH)

Provide general network information such as the cell in which the mobile station is located.

Paging CHannel (PCH)

Call mobile stations when there is an incoming call.

Random Access CHannel (RACH)

Inform the network that there is a mobile station-originated call.

Access Grant CHannel (AGCH)

Assign a dedicated control channel to the mobile station.

Cell Broadcast CHannel (CBCH)

Transmit cell broadcast information.

For more information, refer to “Control Channels” (p. 2-42).


1-13

Introduction to GSM

GSM Functions

....................................................................................................................................................................................................................................

....................................................................................................................................................................................................................................

1-14


2

2 Alcatel-Lucent BSS

Overview Purpose

This section provides an overview of the Alcatel-Lucent BSS, its functions and features. Contents BSS Overview

2-1


2-6

External Components

2-16

Alcatel-Lucent BSS Functions

2-25

Extended GSM in the Alcatel-Lucent BSS

2-27

Telecommunications Layers in the Alcatel-Lucent BSS

2-30

Network Management and the Alcatel-Lucent BSS

2-48


2-50

BSS Overview Overview

The Alcatel-Lucent BSS is responsible for handling traffic and signaling between a mobile phone and the NSS. The BSS carries out transcoding of speech channels, allocation of radio channels to mobile phones, paging, quality management of transmission and reception over the Air interface and many other tasks related to the radio network. The following figure shows the Alcatel-Lucent BSS within the PLMN, and its links to the PSTN and the PSDN in a fixed network.


2-1

Alcatel-Lucent BSS

BSS Overview

....................................................................................................................................................................................................................................

Legend:

MFS


NMC

Network Management Center

PSDN

Packet Switched Data Network

PSTN


SGSN


Alcatel-Lucent Radio Solutions

To respond to the swiftly evolving needs in the BSS, Alcatel-Lucent offers specific Radio Solutions. The Alcatel-Lucent Radio Solutions include the following BSS equipment: •

9120 BSC

•

9130 BSC

•

G2 Transcoder

....................................................................................................................................................................................................................................

2-2


Alcatel-Lucent BSS

BSS Overview

....................................................................................................................................................................................................................................

•

9125 Transcoder

•

BTS 9100

•

BTS 9110

•

Distributed BTS

•

Macro BTS

•

9130 MFS.

For more information, refer to “Alcatel-Lucent BSS Components” (p. 2-6). Frequency Band Configurations

The Alcatel-Lucent BSS supports the following multiband network configurations: •

BSS with a mix of GSM 850 and GSM 1900 cells

•


•


•

BSS with a mix of GSM 900 and GSM 1900 cells.

Extended GSM Band (E-GSM)

The Alcatel-Lucent BSS supports the E-GSM band. E-GSM consists of: •

The 900 MHz primary band, called the P-GSM band. This uses 890-915 MHz for uplink, and 935-960 MHz for downlink

•

The 900 MHz extended band, called the G1 band. This uses 880-890 MHz for uplink, and 925-935 MHz for downlink.

This corresponds to a total number of 174 addressable frequencies. GPRS

The Alcatel-Lucent BSS supports GPRS, the solution chosen by the ETSI in response to the demand for increased data transmission rates. This means there are now two parallel systems in the PLMN: •

Circuit-switched transmission for voice

•

Packet-switched transmission for data.

For an overview of the different PLMNs, refer to: •

“Standard GSM PLMN” (p. 1-3)

•

“GSM/(E)GPRS PLMN” (p. 1-4).

For information about how GPRS functions in the BSS, see Chapter 3, “GPRS in Alcatel-Lucent BSS”.


2-3

Alcatel-Lucent BSS

BSS Overview

....................................................................................................................................................................................................................................

IP Transport Mode

The IP transport in GSM project replaces the existing TDM based transport with an IP based transport. There are two modes: •

Mixed mode BSS contains both TDM BTS and/or IPoEth BTS. It needs an IP backbone on Ater.

•

Full IP BSS no longer contains TDM BTS and/or IPoEth.

There are three modes: •

Mixed mode BSS contains both TDM BTS and/or IPoEth BTS. It needs an IP backbone on Ater.

•

Full IP BSS no longer contains TDM BTS and/or IPoEth

•

Full IPoEth BSS only uses IPoEth (there are no more Abis links that use IPoE1).

There are two stages: •

IPoE1 (Abis on E1, Ater on Eth)

•

IPoEth (Abis on Eth, Ater on Eth).

The stage is : IPoEth (Abis on Eth, Ater on Eth). There are two types of network access: •

Layer2 Transport Network Using a Layer 2 transport network means that, despite the BSS, NEs (BTS, BSC, TC, MFS) will still exchange IP packets, and the underlying functional architecture of the transport network is seen as a single LAN.

•

Layer Transport Network.

The IP transport mode is supported only in 9130 MFS, 9130 BSC, Alcatel-Lucent BTS (with SUM-X board) and 9125 TC (with TCIF IP board). IP external routers management in: •

BSC The BSC performs a leachability test an –

OEM address (REACHABILITY_TEST_ADDR_O&M)

–

several telecom addresses (REACHABILITY_TEST_ADDR_BSS, REACHABILITY_TEST_ADDR_ASIG) They are supplied by the operator (on POLO or BSC Terminal). The reachability test is performed by the active OMCP on both the active and standby switch sides for the two (O&M and telecom) reachability test addresses.

•

TC The TC operates along the same principles as the BSC.

•

MFS

....................................................................................................................................................................................................................................

2-4


Alcatel-Lucent BSS

BSS Overview

....................................................................................................................................................................................................................................

The MFS has two reachability addresses for O&M (REACHABILITY_TEST_ADDR_O&M) and telecom (REACHABILITY_TEST_ADDR_TELECOM). They are supplied by the operator. The telecom address is tested by the GP on its active side so that the GP can swap to the standby side if required. The O&M address is used by the Control Station for both switch side management and supervision purposes. STM1 Topology

In order to decrease the cost of transport in the BSS, Alcatel-Lucent provides an alternative solution to TDM transport, STM1 (Synchronous Transport Mode level 1) in the Synchronous Digital Hierarchy (SDH) network. STM1 permits the transportation of larger amounts of telephone calls and data traffic over the same fiber wire without synchronization problems, using lasers or light-emitting diodes (LED). Figure 2-1 Synchronous Transport Mode level 1 (STM1)


2-5

Alcatel-Lucent BSS

BSS Overview

....................................................................................................................................................................................................................................

This feature is currently only available for the 9130 BSC Evolution, and four STM1s can be connected on the front plate of the new TPGSMv3 board. The basic unit of framing in SDH is a STM1 (Synchronous Transport Module level 1), which operates at 155.52 Mbit/s, and is used in GSM solely for transporting E1 links. The SDH is used in the canalized mode. Each E1 link is transported transparently (using asynchronous mapping) in one VC12 container. One STM1 link can contain up to 63 VC12 containers. Therefore, one STM1 can carry 63 Abis and/or Ater, and each E1 of 2048 kbps is transported separately on one VC12 container. A VC12 container is also called a VC12 tributary, and performs the mapping between E1 and VC12. The VC12 (TU12) tributaries are numbered according to G.707: (K, L, M) with: • K=1..3 • L=1..7 • M=1..3 The numbers go from (1,1,1) to (3,7,3). In total, there are 63 tributaries. A tributary on TPGSMv3 is therefore identified by: X, K, L, M; with x=1..4 as the STM1 link number. This feature provides the following benefits. It: •

Reduces the cabling effort

•

Reduces the space needed for cables and distribution frames

•

Simplifies cabling/assignment changes

•

Reduces the cost of transmission equipment

•

Increases the reliability and availability.

Alcatel-Lucent BSS Components Overview

There are three main units in the Alcatel-Lucent BSS: •

The BSC, which acts as the controller of the BSS. The BSC provides control of the BTS and their resources, and performs switching functions within the BSS.

•

The BTS, which provides the radio transmission and reception functions for a cell

•

The Transcoder, which performs rate adaptation and encoding/decoding of speech and data between the MSC and the BSC.

Refer to Figure 1-1, “Base Station Subsystem” (p. 1-7).

....................................................................................................................................................................................................................................

2-6


Alcatel-Lucent BSS


....................................................................................................................................................................................................................................

The BSS is supervised by the OMC-R. In a large network, one or more high-level supervisors, such as NMCs, can exist to centralize network management activities. The NMC has the authority to send directives to the OMC-R. For more information about the NMC, refer to documentation supplied with the NMC. For more information about the OMC-R, refer to “Operations and Maintenance Center-Radio” (p. 2-24). Base Station Controller

The BSC provides control of the BTS and manages radio resources and radio parameters. From a transmission point of view, the BSC also performs a concentration function if more radio traffic channels than terrestrial channels are connected to the MSC. A single BSC can control a large number of BTS. The exact number is a function of the BSC equipment and the configurations used. The BSC provides: •

Resource management

•

Database management

•

Radio measurement processing

•

Channel management

•

Operations and maintenance functions within the BSS

•

Communication with the OMC-R

•

Switching between the Air Interface channels (and their associated Abis channels), and the A Interface channels. For more information about these interfaces, refer to: – “A Interface” (p. 2-33) – “Abis Interface” (p. 2-37) – “Air Interface” (p. 2-39).

The 9120 BSC also incorporates the following transmission equipment: •

The Base Station Interface Equipment (BSIE), which performs signaling and submultiplexing on the Abis Interface

•

The Transcoder Submultiplexer Controller (TSC), which collects and processes transmission data. It also provides an operator interface to certain transmission functions via a Local Maintenance Terminal.

For a more detailed description of the 9120 BSC, refer to the Alcatel-Lucent BSC / TC Overall Description.


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The antennae transmit and receive, and the receive path is duplicated up to the TRE, providing the same gain in efficiency and low-power mobile station range. The following figure shows the antenna diversity path through the BTS 9100.

Legend:

ANT

Antenna

ANx

Antenna Network Type x

ANy

Antenna Network Type y

SUM

Station Unit Module

TRE

Transmitter/Receiver Equipment


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Note: The configuration shown above (1 Sector, 3X4 Transceivers) is one example only. Other combinations of Antennae and TREs are possible. There is no ANy in the BTS 9110, and ANy is not needed if the sector has two TREs. Antenna Hopping

Antenna hopping means that the sequence of bursts comprising a radio block are transmitted over more than one antenna. The purpose is to get diversity of the radio path to the mobile. In conjunction with frequency hopping, the number of paths provided by frequency hopping can be multiplied with the number of antennas involved in the antenna hopping. The feature is intended to be provided by the twin module. Antenna hopping can be used if: •

The two TRE of a twin module are connected to different antennas of the same sector (cell)

•

The mate TRE of a twin module is in traffic

•

TxDiv feature is not used

•

The number of antennas for antenna hopping is two.

To avoid the loss of a complete sector in the case of Twin module failure, it is recommended for small BTS configuration to configure each TRE of a Twin in different sector.

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A TRE is antenna hopping capable if: •

TxDiv capability is true

•

TxDiv usage is false

Antenna hopping is activated only on BTS configured with all TRE full rate or all TRE dual rate Transcoder And Transmission Functions

The Transcoder is the key component for the transmission function, which provides efficient use of the terrestrial links between the equipment of the BSS. In addition to the Transcoder, Submultiplexers are also used for transmission functions. The Transcoder provides: •

Conversion between A-law and Radio Test Equipment-Long Term Prediction encoded traffic (speech)

•

Conversion between A-law and Algebraic Code Excited Linear Prediction encoded traffic (speech)

•

Rate adaptation (data)

•

O&M control of the transmission function.

The Transcoder is normally located next to the MSC. The Submultiplexer performs submultiplexing on the Ater Interface, between the MSC and the BSC. When submultiplexing is used, a Submultiplexer is located at each end of the link. The following figure shows how transmission components are distributed in the BSS with a 9120 BSC.


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Legend:

Base Station Interface Equipment

BIE

SM

Submultiplexer Transcoder Submultiplexer Controller

TSC

TC

Transcoder

A BSS with the 9130 BSC differs from BSS with the 9120 BSC, in that the transmission components are replaced by virtual transmission processors. There are two types of transcoders: •

G2 There are 2 types of G2 TC: –

G2 TC equipped with ASMC and TRCU

–

G2 TC equipped with ASMC/TRCU + MT120 boards (in the case of an extension).

• 9125 ....................................................................................................................................................................................................................................

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The 9125 TC can be equipped with up to 48 sub-units (referred to as MT120 boards). Each MT120 offers an Atermux connection to a BSC and up to 4 Atrunk connections to the MSC. The 9125 Compact TC can have 2 9125 TC STM1 boards, active and standby. They are inserted in a dedicated 9125 TC STM1 subrack, which is located in the bottom part of the TC rack. Each TC MT120 board is connected to both TC 9125 STM1 boards (dual star). Multi-BSS Fast Packet Server

The MFS is preferably located at the Transcoder/MSC site. It is internal to the BSS and provides the following functions: •

•

PCU (Packet Control Unit) functions Comprising: –

PAD (packet assembly/disassembly) function

–

Scheduling of packet data channels

–

Automatic Retransmission Request functions

–

Channel access control functions

–

Radio channel management functions.

The Gb Interface protocol stack.

The MFS converts GPRS frames, carried on multiple 16 kb/s links from multiple BTS, to one or more frame relay channels connected to the SGSN on the Gb Interface. For more information, refer to “Gb Interface” (p. 3-13). The set up of Packet Data Channels is controlled by the MFS. It also negotiates resources with the BSC and routes GPRS packets. When an additional channel is required on a BTS, the MFS asks the BSC to allocate a channel and to connect it to an Ater channel which the MFS controls. The Alcatel-Lucent solution also supplies two dedicated GPRS interfaces between the MFS and the BSS: •

The BSCGP Interface supplies routing of GPRS messages and resource negotiation between the BSC and the MFS

•

The GCH Interface routes user data traffic and signaling between the MFS and the BTS transparently (to the BSC).

The MFS provides a terminal interface, the IMT, for local O&M of the MFS. GPRS Processing Units

The MFS is divided into GPRS Processing Units (GP) which are interconnected via an Ethernet bus and controlled by a control station. The GP handles the O&M and telecom functions of several cells, but a cell cannot be shared between several GPs.


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A GP cannot be connected to more than one BSC, which means that each GP cannot manage several BSSs simultaneously. Even so, the use of several GPs per BSS is required for traffic capacity reasons. The MFS is in charge of associating each cell with a GP. This is referred to as GP cell mapping. The GP is in charge of: •

•

O&M functions Comprising: –

Initialization of the MFS

–

Software download

–

Software configuration

–

Performance monitoring.

Telecom functions Comprising: –

Radio and transmission resource control

–

Radio link control of packet connections

–

Common control channel management

–

MS radio resource control

–

Logical Link Control (LLC)

–

Protocol Data Unit (PDU) transfer

–

Multiframe management

–

Congestion control

–

Gb Interface management

–

Signaling management on the GSL interface.

In IP transport mode, the BSS bases the IPGSL, TCSL and the IPGCH control link on a TCP connection: •

Between the 9130 MFS GP and the 9130 BSC CCP for the IPGSL As follows: –

In the case of IP BSS, there is one IPGSL per GP

–

The IPGSL IP addresses and port numbers are fixed (OAM) on both GP and CCP sides

–

In IP mode, the IP GSL uses a (unique) TCP connection between the GP and the BSC (CCP board).

•

Between the 9130 MFS GP and the BTS TRE for IPGCH

•

Between the 9130 BSC OMCP and the TC TCIF for the TCSL.

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GP Protocol Management

The GP is split into two sub-units: •

The Packet Management Unit (PMU), and

•

The Packet Traffic Unit (PTU).

The protocols handled by a GP are split in the following manner: •

Protocols handled by the PTU: Including: –

Radio interface protocols (RLC and MAC)

– GCH interface protocols (L2-GCH and L1-GCH). The PTU manages the corresponding GCH Interface; for more information, refer to “GCH Interface” (p. 3-16). •

Protocols handled by the PMU: Including: –

Gb interface protocols (BSSGP, Network Service, and Full Rate)

–

BSC interface protocols (BSCGP, L2-GSL, and L1-GSL)

– The RRM protocol. The PMU manages the corresponding Gb and GSL interfaces. Multi-GP per BSS

To increase the GPRS capacity of the BSS in terms of the number of PDCH, several GP boards can be connected to the BSC to support the PCU function. This feature is applied regardless of the BTS type. For one BSC, in the case of a multi GP configuration, if the last GSL of any GP is lost, all GPs assigned to the BSS will be reset ( reset_data) and PS outage occurs. The only exceptions are the following: •

GSL loss on GP which have all cells locked

•

GSL loss on GP and the other GP have also their GSL down.

Cell Mapping

Mapping a cell means that a cell is associated with a GP. Remapping a cell means that a cell, already linked to a GP, is moved to another GP. The mapping of cells onto GPs is performed by the MFS, which actually defines the mapping of cells onto LXPUs (logical GP). An LXPU is either the primary GP, or the spare GP in the case of switchover. All the GPRS traffic of one cell is handled by only one GP. The following figure shows an example of cell mapping.


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Legal notice Legal notice

Alcatel, Lucent, Alcatel-Lucent and the Alcatel-Lucent logo are trademarks of Alcatel-Lucent. All other trademarks are the property property of their respective respective owners. The information presented is subject to change without notice. Alcatel-Lucent assumes no responsibility for inaccuracies contained herein. Copyright Copyr ight © 2012Alcatel-Luc 2012Alcatel-Lucent. ent. All rights reser reserved. ved. Note:

Not to be used or disclosed except in accordance with applicable agreements.

Alcatel-Lucent B12 BSS Overview

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