Nokia Bss Transmission

BSC3119 Nokia BSC/TCSM, Rel. S12, Product Documentation, v.1

Nokia BSS Transmission Configuration

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The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia's customers only for the purposes of the agreement under which the document is submitted, and no part of it may be reproduced or transmitted in any form or means without the prior written permission of Nokia. The document has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia welcomes customer comments as part of the process of continuous development and improvement of the documentation. The information or statements given in this document concerning the suitability, capacity, or performance of the mentioned hardware or software products cannot be considered binding but shall be defined in the agreement made between Nokia and the customer. However, Nokia has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia will, if necessary, explain issues which may not be covered by the document. Nokia's liability for any errors in the document is limited to the documentary correction of errors. NOKIA WILL NOT BE RESPONSIBLE IN ANY EVENT FOR ERRORS IN THIS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of this document or the information in it. This document and the product it describes are considered protected by copyright according to the applicable laws. NOKIA logo is a registered trademark of Nokia Corporation. Other product names mentioned in this document may be trademarks of their respective companies, and they are mentioned for identification purposes only. Copyright © Nokia Corporation 2007. All rights reserved.

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Contents

Contents Cont Conten ents ts 3 List List of tabl tables es 5 List List of figu figure res s

6

Summa Summary ry of chan change ges s

9

1

BSS transmission

2 2.1 2.2 2.3 2.4 2.5

BSC configuration 19 BSC location 19 BSC capacity limits 19 A and Ater BSC interface 22 Int Interface to the the OMC dire irection LAN interfaces 22

3 3.1 3.2 3.3 3.3 3.4

TC configuration 25 Installations with TCSM 25 TCSM3i versus TCSM2 28 TCSM3 TCSM3ii vers versus us TCSM3 TCSM3ii for for comb combin ined ed BSC3i BSC3i/TC /TCSM3 SM3ii inst instal alla lati tion on TCS TCSM versus tra transcoder in MGW 29

4 4.1 4.1 4.1. 4.1.1 1 4.1. 4.1.2 2 4.2 4.3

BTS configuration 31 TRU TRU tran transm smis issi sion on unit unit des descrip cripti tion ons s 33 O & M arran rrang gemen ementt of tran trans smis mission sion 34 Opti Optio ons for for tran transm smis iss sion ion 35 FC and FXC units 36 FIEA, FIPA and FIFA units 38

5 5.1 5.2 5.3

GPRS and the Gb interface Gb over Frame Relay 41 Gb over IP 44 GPRS capacity 44

6

BSS redundancy configurations

7 7.1 7.2 7.3

Ope Operati ration on and main mainte tena nanc nce e of tran transm smis issi sion on equi equipm pmen entt Supervisory channels 49 Local O & M 50 Remote O & M 52

8 8.1 8.2 8.3 8.3 8.4 8.4 8.5

Requirements on transmission network 53 2 Mbit/s transmission paths 53 Syn Synchronisatio tion of BSS netwo twork 55 Trans ransmi miss ssio ion n dela delay y of BSS BSS netw networ ork k 57 Erro Errorr rate rate perf perfor orma manc nce e of BSS BSS netw networ ork k 57 Slips in transmission 58

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29

41

47 47 49

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8.6 8.7

Echo control in BSS 59 Jitter and wander prevention in BSS

9 9.1 9.2

Digital cross-connect nodes 61 Digital node equipment DN2 62 MetroHub transmission node 63

10 10.1 10.2 10.3 10.4 10.5 10.6 10.7

BSC-BTS transmission examples 67 Overview of transmission network 67 Point-to-point transmission 68 Multidrop chain transmission 68 Loop transmission 69 Radio transmission 70 DN2 in the MSC-BSC path 70 Nokia UltraSite network example 71

11 11.1 11.2 11.3 11.4 11.5 11.6

Time slot allocations in BSS 73 Time slot allocation in combined BSC3i/TCSM3i installation (ANSI) Compressed Abis time slot allocation 82 Allocation of Abis time slots 86 TRU TSL allocation, FR, 16 kbit/s signalling 87 TRU TSL allocation, FR/HR, 64 kbit/s signalling 90 TRU TSL allocation, FR/HR, 32 kbit/s signalling 90

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List of tables

List of tables Table 1.

BSC configurations

20

Table 2.

Number of BCSUs in combined BSC3i/TCSM3i installation

Table 3.

Circuit types of TCSM2 and TCSM3i

Table 4.

Matching of circuit type and circuit pools

Table 5.

The transmission units in the Nokia Talk-family and Nokia PrimeSite BTSs 33

Table 6.

SAPI values and priorities

Table 7.

Connectivity of logical PCUs

Table 8.

Compressed Abis time slot allocation

Table 9.

Compressed Abis time slot allocation in the case of multi-TRX base stations 83

20

25 26

38 45 83

Table 10. Compressed Abis time slot allocation that supports five 3 x 1 TRX sites 83 Table 11. Compressed Abis time slot allocation with the TRX signalling speed 32 kbit/s 84 Table 12. 16 kbit/s signalling rate

86

Table 13. 64 kbit/s signalling rate

87

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List of figures Figure 1.

General BSS/RAN topology: access through multiservice network

Figure 2.

Through-connected channels configured in the transcoders and in the MSC switching matrix 42

Figure 3.

GPRS traffic multiplexed on the same physical connection as used for the GSM traffic on the Ater interface 42

Figure 4.

GPRS traffic concentrated and carried over the Gb interface in a packet data network 43

Figure 5.

GPRS traffic carried over dedicated 2 Mbit/s PCM links

Figure 6.

GPRS traffic carried over the Gb interface with IP

Figure 7.

Radio link hop protection

Figure 8.

Interconnection of different networks

Figure 9.

Multiplexing of the BSS and external channels with the DN2

Figure 10. Network principle

43

44

48 61 63

64

Figure 11. BSS network using leased lines

67

Figure 12. Point-to-point connection between BSC and BTS Figure 13. Multidrop chain

13

68

69

Figure 14. Duplicated point-to-point and multidrop loop Figure 15. Loop, radio relay transmission network Figure 16. Example use of the DN2

69

70

71

Figure 17. Example of a Nokia UltraSite network

72

Figure 18. Time slot allocation for 16 kbit/s bit rate channels (typically full rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface with the TCSM2/TCSM3i 75 Figure 19. Time slot allocation for half rate traffic with 8 kbit/s TRAU frames on the Ater 2 Mbit/s interface with the TCSM2 76 Figure 20. Ater time slot allocation example for the HSCSD application: a combination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/s channels (HS4) 78 Figure 21. Time slot allocation of 2 x 16 kbit/s channels of Figure A-PCM1 on A interface 79 Figure 22. Time slot allocation of 4 x 16 kbit/s channels of Figure A-PCM2 on A interface 79

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List of figures

Figure 23. Submultiplexing on Ater PCM in ANSI environment (16 kbit/s)

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81


81

Figure 26. Submultiplexing on Ater PCM in ANSI environment (mixed 32 and 64 kbit/ s) 82 Figure 27. Compressed allocation enabling up to 15 TRXs per 2 Mbit/s circuit Figure 28. Allocation example for a three-TRX BTS

85

86

Figure 29. TRU chain allocation in the case of 16 kbit/s LAPD

89

Figure 30. An example of four-BTS TRU chain (highway) allocation when 32 kbit/s TRX signalling is used 91

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Summary of changes

Summary of changes

Changes between document issues are cumulative. Therefore, the latest document issue contains all changes made to previous issues.

Changes made between issues 12 and 11 –1 Chapter BSS transmission

Information on SDH/SONET optical interface and TCSM3i for combined BSC3i/ TCSM3i installation added. Chapter BSC configuration

Sections BSC capacity limits and A and Abis BSC interface have been updated with information on new BSC3i variants and TCSM3i. Chapter TC configuration

Information on TCSM3i added. Chapter BTS configuration

Information on Nokia Flexi EDGE base station added. Information on ISDN Abis and TRUC/D transmission units has been removed. Chapter BSS redundancy configurations

Information on Abis chain protection has been removed. Chapter Operation and maintenance of transmission equipment

The number of Q1 supervisory channels supported by the BSC has been changed from 28 to 56. Information on V.11 has been removed.

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Chapter Requirements on transmission network

Section Error rate performance of BSS network has been updated. Chapter Digital cross-connect nodes

Hardware details in section Digital node equipment DN2 have been updated. Information on SXC T has been removed. Chapter BSC-BTS transmission examples

Sections Radio transmission and DN2 in the MSC-BSC path have been updated. Information on SXC T has been removed. Chapter Time slot allocations in BSS

Section Time slot allocation in combined BSC3i/TCSM3i installation (ANSI) has been added.

Changes made between issues 11 –1 and 11 Chapter TC configuration

Information on Multimedia Gateway added.

Changes made between issues 11 and 10 Chapter BSC configuration

Table BSC capacity limits replaced with new table BSC configurations. Sections AMR Half Rate, A and Abis BSC interface and LAN interfaces updated. Section 2 Mbit/s Abis PCM maximum capacity moved from chapter BTS configuration. Chapter TC configuration

Section Installations with TCSM removed. Chapter BTS configuration

Sections Nokia MetroSite, Nokia 2nd generation, Nokia Talk-Family, BIE/ BIU2M module, BIE/BIUMD module removed.

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Summary of changes

Chapter GPRS and the Gb interface

Section Gb over IP added. Section GPRS capacity updated. Chapter BSS redundancy configurations

Contents of the chapter reorganised. Sections Abis redundancy with Nokia 2nd generation BTS, Abis loop with Nokia Talk-family base stations and Abis point- to-point redundancy with Nokia Talk-family base stations removed. Chapter Operation and maintenance of transmission equipment

Contents updated. Chapter Requirements on transmission network

Sections 2 Mbit/s transmission paths,2Mbit/s requirements with EDGE and 2 Mbit/s interfaces combined as 2 Mbit/s transmission paths. Minor updates. Chapter Digital cross-connect nodes

Chapters Service Cross-Connect SXC T and Digital node equipment DN2 combined as Digital cross-connect nodes. Chapter BSC-BTS transmission examples

Sections BIU2M point-to-point, BIUMD chain, TRU line repeater function, Extending Talk-Family Network with MetroSite and Abis spur routes removed. Figure 19 updated. Chapter Time slot allocations in BSS

Sections BIUMD time slot allocations and Special BIUMD configurations removed. Section Compressed allocation combined with section Compressed Abis time slot allocation.

Changes made between issues 10 and 9 –1 The chapters BSS transmission configuration overview and BSS transmission configuration approach have been combined with the chapter BSS transmission , the new name for the chapter BSS transmission generic guidelines . Chapter BSC configuration : added a new section, LAN interfaces . Chapter Requirements on transmission network , section Synchronisation of BSS network : the section has been renewed.

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Changes made between issues 9 –1 and 9 Information on Nokia ConnectSite 10 and Nokia ConnectSite 100 base stations has been added. Chapter BTS configurations , section FC and FXC units : added new subsections Fibre optic transmission and MetroHub transmission node . Subsection FC units without cross-connection : reference to FC RRI has been replaced by FC STM-1. Chapter Requirements on transmission network : new section 2Mbit/s requirements with EDGE added.

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BSS transmission

1

BSS transmission Usually the BSC-BTS Abis transmission configuration is a mixture of point-to point, multidrop chain, or multidrop ring subnetworks.

BSC / RNC

BS

BS

BS

BS

BS

Multi Service SDH or ATM or IP Network

BS BS BS BS

BS

BS BS BS

Access network compatible standard high capacity IF

BS

Access network compatible standard low capacity IF

BS

BS BS

BTS access medium capacity IF

BS

BS BS

BS

BTS access low capacity IF

BS

Access network element BS

Figure 1.

BS

Base station site

General BSS/RAN topology: access through multiservice network

The BSC sees BTSs through 2 Mbit/s PDH ET ports which carry data to and from the BTSs. The transport network in between can be whatever technology when it provides transparent PDH termination points.

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.

Transport network topology The transport network topology can be a star, chain or loop. The star network benefit is that it is very simple to manage but the disadvantages are that the connections are typically only partially filled with payload (extra transmission cost) and any failure in the network causes traffic cut. Use of grooming at star network hub sites will optimise the use of northbound transport capacity. The chain network improves the efficiency of the use of transmission capacity but is still sensitive to failures in the network. From the efficiency and reliability point of view the topology is the loop. The disadvantage in the loop is that the related equipment settings require transmission competence but that can be overcome with training and following the available instructions. Note that all these topologies are transparent for the Abis traffic.

.

Grooming principle Grooming in the network means the cross-connection functions which allow combination of partially filled transmission containers, for example 2 Mbit/s G.704 frame into a single container. Nokia BTS integrated transmission units support this function. The benefit is naturally better efficiency in the transport layer.

.

Synchronisation In the BSS area the BSC is the synchronisation master to the BTSs. Normally the transport layer is also synchronised to the BSC by taking the first transmission equipment synchronisation reference from the master BSC ET port and then delivering this synchronisation in the transmission network downwards. When using other technologies to carry the ET signals, such as SDH, and when the non-PDH network is synchronised to a synchronisation reference on its own, then the ET port synchronisation must be transparently transmitted into the first PDH element through the SDH layer.

.

Network management principles Nokia BTS integrated transmission elements are managed by using the Q1 protocol. The essential parts of that protocol are the location of the polling device (Q1 master), the Q1 data communication channel and the Q1 addressing. The most typical set-up is that the local BTS operates as Q1 master and forwards the Q1 messages to/from the NMS using a BTS management channel in the NMS direction and Q1 channel in the transmission direction. The Q1 data communication channel is a bus where all elements hear all the messages along the bus. The devices are accessed by using a unique address for each element on the bus. Often there are also non-integrated Q1 elements in the BSS network. Those devices are polled

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BSS transmission

either by the BTS or BSC depending on the Q1 plan. Normally the Q1 plan is such that the polling device is closer to the BSC than the polled device to have management access as deep into the network as possible in case of any failures. BSS transmission configuration approach

The focus here is mainly on BSC-BTS transmission. The start of the whole BSS design procedure relies on BSS traffic handling requirements. The specific information needed in planning and dimensioning the network includes the following items: .

BTS locations and sizes

.

BSC location

.

MSC location

.

Transcoder equipment location

.

Available transmission methods

The support of half rate speech coding is introduced with BSS5. This approximately doubles the voice traffic carrying capacity of the GSM network. The introduction of EDGE air interface enables a four-fold data rate per call and the raw implementation of EDGE would require four-fold transmission capacity. Dynamic Abis is introduced to optimise the use of Abis for EGPRS purposes. The design starts from the BTS information, followed by the BSC, the TCSM, and the MSC. For the transmission part of the network, the following input data is needed for dimensioning: 1.

The number of traffic channels on the A interface per BSS, full rate (FR/ EFR), half rate (HR), AMR, High Speed Circuit Switched Data (HSCSD), General Packet Radio Service (GPRS) and the number of EDGE TRXs .

.

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The number of transcoder units (either TCSM2 or TCSM3i), their capacities and BSC A interface connections can be deduced from this number. HSCSD will set special requirements for Ater capacity depending on how many HSCSD circuits are used and how many parallel time slots are supported by the transcoder. A given transcoder pool may support both FR/EFR/HR and multislot HSCSD.

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.

.

.

.

2.

GPRS service is implemented by a plug-in unit (PCU) in the BSC. For more information, see GPRS and the GB interface.. Optical STM-1/OC-3 (SDH/SONET) interface can be used to increase the external connectivity of the BSC3i and reduce the transmission costs. One STM-1 interface consists of 63 ETs (ETSI) and one OC-3 interface of 84 ETs (ANSI). As a standard up to 6 BSCs (optionally up to 12 BSCs) can be connected to one TCSM3i in stand-alone installation. In combined BSC3i/TCSM3i installation, the transcoding capacity of a TCSM3i can be shared by up to 96 BSCs (ETSI) or 24 BSCs (ANSI).

The total number of TRXs controlled by the BSC .

.

3.

Each HSCSD channel occupies an entity of 64 kbit/s (one time slot) at the A interface. However, the data stream itself may be carried by less than 8 bits of the time slot.

If Dual Band is in use, the TRXs operate in different frequency bands. The capability of the BSC processing can be deduced from this number.

The total number of 2 Mbit/s links on the BSC Abis interface The number of BSC Abis 2 Mbit/s connections can be deduced from this number. EDGE TRX can be connected using a shared Dynamic Abis pool which allows dynamic allocation of capacity wherever it is needed. The dimensioning of Dynamic Abis is explained in Abis EDGE Dimensioning in GSM/EDGE BSS System Documentation Set.

Once the required transmission capacity has been calculated, the transmission network planning may start. The BSS transmission network planning is based on: .

Required BSC BTS Abis capacity

.

Required Ater capacity

.

Required Gb capacity

.

Required IP connectivity

.

Existing and/or available transmission network and its tariffing

.

Decision on traffic protection

.

Network management solution

The details of transmission network planning include:

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BSS transmission

.

.

Allocating required capacities into usable conduits (such as leased lines and radio links) 2M time slot allocation plan for each BSC BTS Abis link, taking into account the Dynamic Abis for EDGE

.

Transmission capacity optimisation by grooming cross-connections

.

Loop network protection planning

.

.

Network management channel planning Synchronisation hierarchy planning

When the transmission network high level planning is done, the related transmission settings can be entered to the equipment to make the network operate. Related topics .

.

.

.

.

.

TC configuration BTS configuration GPRS and the Gb interface BSS redundancy configurations Operation and maintenance of transmission equipment

.

Requirements on transmission network

.

Digital cross-connect nodes

.

BSC - BTS transmission examples

.

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BSC configuration

Time slot allocations in BSS

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BSC configuration

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BSC configuration The BSC configuration process includes two steps: 1.

To determine the BSC location in the BSS network

2.

To determine the configuration of each BSC

The switching field GSWB of the BSC meets both full rate and half rate speech requirements.

Note The dimensioning principles for enhanced full rate (EFR) channels are the same as for FR channels.

2.1

BSC location Locating BSCs in the BSS network is flexible. BSCs can be co-located or non-colocated with the MSC and the transcoder. The best location depends mainly on tariff structure on transmission lines. For example, if the tariff correlates strongly with the distance of the transmission line, the best location for a BSC is normally non-co-located with the MSC and the TC. Transmission lines can be saved on the A interface by submultiplexing and concentrating the traffic on fewer lines. Concentration can save a lot of expenses because the number of lines can be dimensioned according to the expected volume of traffic. For more information, see Engineering for BSC3i.

2.2

BSC capacity limits There are certain limits to the capacity, especially to the number of TRXs and the number of PCM lines. These limits are presented in the table below.

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Table 1.

BSC configurations

BSC configurations

BSC2i

BSC3i 660 / BSC3i 1000 / BSC3i 2000

Maximum radio network configuration

248 BCF

504/1000/2000 BCF

248 / 512 BTS

660/1000/2000 BTS

512 TRX

660/1000/2000 TRX

Maximum number of external PCMs

80 / 112 / 144

256/384/800

SS7 signalling links

16

16

Minimum number of WO-EX BCSUs

1-8

1-6/1-5/1-10

Number of BCFSIG LAPD links per BCSU

32

84/200/200

Number of TRXSIG LAPD links per BCSU

64

110/200/200

Maximum number of LAPD links per BCSU

124

206/412/412/

512

880/1600/1600

(BCFSIG + TRXSIG + ETLAPD) Maximum number of TCHs per BCSU

To ensure full LAPD signalling capacity for combined BSC3i/TCSM3i installation, there must be a certain number of working BCSUs in the master BSC. The exact number depends on the radio network configuration as follows:

Table 2.

Number of BCSUs in combined BSC3i/TCSM3i installation

RNW configuration

Number of BCSUs

1 TRX under BTS

5

6 TRXs (2+2+2) under BTS

1

For more information, see the following BSC product descriptions: .

Product Description of Nokia Base Station Controller BSC3i

.

Product Description of Nokia Base Station Controller BSC2i, BSCi

2 Mbit/s Abis PCM maximum capacity

The capacity depends on the signalling rate:

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BSC configuration

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.

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16 kbit/s LAPD signalling links (mainly for FR but also HR) can handle up to 12 TRXs and up to 12 Operation and Maintenance Units (OMUs) on a single 2 Mbit/s line. 32 kbit/s LAPD signalling links (optimised for HR) can handle up to 12 TRXs and up to 4 OMUs on a single 2 Mbit/s line. 64 kbit/s LAPD signalling links can handle up to 8 TRXs and up to 7 OMUs, or up to 9 TRXs and up to 4 OMUs, or up to 10 TRXs and 1 OMU on a single 2 Mbit/s line; in new installations, 64 kbit/s TRX or OMU signalling data rate is not normally used because it results in a high requirement of capacity

For the best transmission economy, the PCM lines should be packed as full as possible. The methods of doing this are explained later. AMR Half Rate

Introduction of Adaptive Multi-Rate codec (AMR) Half Rate (HR) causes increased load in measurement reporting; therefore it can happen that a capacity of 16 kbit/s LAPD signalling link is not sufficient in all cases. When the TRX contains merely HR or dual rate (DR) traffic channel (TCH) resources, the situation becomes even worse if the stand-alone dedicated control channels (SDCCH) have also been configured on the TRX. Therefore a 32 kbit/s LAPD link has been introduced to support the telecom signalling. AMR codecs support in Nokia BSC and TCSM2/TCSM3i: .

.

.

.

.

All Nokia BSCs have full AMR support, except 7.95 kbit/s on HR channel. Nokia TCSM2 and TCSM3i have full AMR support. A TC PCM pool type is needed for transcoder configuration on the A interface. The AMR pool type, which supports AMR FR and AMR HR (pool 23 in TCSM2 and pools 23, 28 and 32 in TCSM3i), is implemented. Submultiplexing on highway PCM is 8/16 kbit/s, for example if AMR FR (16 kbit/s) is used on the Abis interface, the Ater interface rate is also 16 kbit/s. Correspondingly if AMR HR (8 kbit/s) is used on the Abis interface, the Ater interface rate is 2 x 8 kbit/s (the BSC transmits ones (= bit value 1) on the unused 8 kbit/s sub-timeslot).

With the AMR HR implementation, the BSC's maximum channel capacity of 4096 must be taken into account in dimensioning the number of TRXs in the BSC. For example the traffic processing capacity of the BSC2i supports 512 full rate TRXs or 256 half rate TRXs. Connectivity for 512 half rate TRXs is available with Soft Channel Capacity application software.

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BSC TRX capacity can be maintained by using FR to HR load threshold parameters. The maximum channel capacity of the BSC3i is 5280. BSC3i supports up to 2000 full rate TRXs or up to 1000 half rate TRXs. Connectivity for 2000 half rate TRXs is available with Soft Channel Capacity application software.

2.3

A and Ater BSC interface In TCSM2, the A and Ater interfaces are supplied by ET2E/ET2A plug-in units with two PCM connections per board). Connector line impedance on 2 Mbit/s trunk lines is either 75 ohm (coaxial, asymmetric) or 120 ohm (pair, symmetric). In TCSM3i, the A and Ater interfaces are supplied by ET16 plug-in units. In TCSM3i for combined BSC3i/TCSM3i, it is also possible to use STM-1/OC-3 (SDH/SONET) optical interface, in which case the A interface is supplied by ETS2 plug-in units. The transmission performance of the interfaces is supervised by the BSC according to ITU-T recommendations.

2.4

Interface to the OMC direction The OMC connection of the BSC can be one of the following: .

.

.

one 2 Mbit/s A interface time slot one ethernet interface according to IEEE 802.3, either 10Base5 (AIU), 10Base2 (COAX) or 10BaseT (TPI); the data rate is 10 Mbit/s an X.25 data terminal equipment (DTE) interface with the alternatives V.24, V.35, V.36 and X.21.

Redundant OMC connections can be achieved by using, for example, X.25 on two separate trunk lines.

2.5

LAN interfaces Various types of IP traffic are transported between network elements with IP connections. The three main types that are relevant to transmission planning are:

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BSC configuration

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NetAct ™ link (O&M traffic) There is O&M traffic in every network element.

.

Signalling traffic with other network elements The Lb interface towards a stand-alone Serving Mobile Location Center (SMLC) and BSC-BSC interface with Dynamic Frequency and Channel Allocation (DFCA) or other LAN connections can be used in the future.

.

Packet traffic IP connectivity can be used for Gb interface with packet traffic. Some other functionalities will also use IP connectivity for packet traffic in the future.

Before starting to build the IP network, see BSC site architecture and IP network topology in BSC Site IP Connectivity Guidelines. See also Nokia Packet Backbone for Mobile Networks, available in 3G Core Network System Information Set. For an overview, see BSS transmission.

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TC configuration

3

TC configuration

3.1

Installations with TCSM TCSM refers to the second and third generation BSS transcoder-submultiplexer equipment, which provides transcoding for traffic channels in the GSM/EDGE networks. The TCSM is located between the MSC and the BSC. Normally, to save transmission capacity, the equipment is located at the MSC site. It can, however, also be situated at the BSC site. With reference to the 3GPP TS 08.08, the circuit types listed in table Circuit types of TCSM2 and TCSM3i are available for use in connection with the TCSMs.

Table 3. Circuit type

Circuit types of TCSM2 and TCSM3i

Supported channels and speech coding in TCSM2

A

FR speech, EFR speech, FR data (14.5, 12, 6 or 3.6 kbit/s)

B

HR speech, HR data (6 or 3.6 kbit/s)

C

FR speech, EFR speech, HR speech, FR data (14.5, 12, 6 or 3.6 kbit/s), HR data (6 or 3.6 kbit/s)

D

FR speech, EFR speech, HR speech, FR data (14.5, 12, 6 or 3.6 kbit/s), HR data (6 or 3.6 kbit/s), HSCSD max 2 x FR data (14.5, 12 or 6 kbit/s)

E

FR speech, EFR speech, HR speech, FR data (14.5, 12, 6 or 3.6 kbit/s), HR data (6 or 3.6 kbit/s), HSCSD max 4 x FR data (14.5, 12 or 6 kbit/s)

F

AMR speech

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Supported channels and speech coding in TCSM3i

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Table 3.

Circuit types of TCSM2 and TCSM3i (cont.)

G

1 (FR) / 16 kbit/s 3 (DR) / 16 kbit/s 5 (EFR&FR) / 16 kbit/s 7 (EFR&DR) / 16 kbit/s 20 (EFR&DR&D144) / 16 kbit/s 23 (AMR) / 16 kbit/s 28 (EFR&DR&AMR&D144) / 16 kbit/s

H

10 (HS2) 2 x 16 kbit/s 21 (HS2&D144) / 2 x 16 kbit/s

I

13 (HS4) 4 x 16 kbit/s 22 (HS4&D144) / 4 x 16 kbit/s 32 (EFR&DR&AMR&HS4&D144) 4 x 16 kbit/s

Table Matching of circuit type and circuit pools shows the matching of pools from the point of view of the TCSM2/TCSM3i and BSC. For the numbering of the pools, see 3GPP TS 48.008 .

Table 4.

Matching of circuit type and circuit pools

TCSM type

BSC circuit pool number

Transcoder circuit type TCSM2/TCSM3i

TCSM2, TCSM3i

1

A/G

2

B/-

3

C/G

5

A/G

7

C/G

10

D/H

13

E/I

20

C/G

21

D/H

22

E/I

23

F/G

28

-/G

32

-/I

TCSM3i

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TC configuration

AMR implementation with TCSM2

A TC PCM type is needed in transcoder configuration of the A interface. The basic AMR type, which supports AMR FR and AMR half rate (HR, pool 23), is implemented for TCSM2. Submultiplexing on highway PCM is 8/16 kbit/s. For example if AMR FR (16 kbit/s) is used in the Abis interface, then the Ater interface rate is also 16 kbit/s. Correspondingly if AMR HR (8 kbit/s) is used in the Abis interface, the Ater interface rate is 2 x 8 kbit/s (BSC transmits ones (= bit value 1) on the unused 8 kbit/s sub-timeslot).

Note The circuit pools 4, 6, 8, 9, 11, 12, 15, 16, 17, 18, and 19 are not supported, but they are all included in at least one of the supported pools (18 in 21, for example). The circuit pools 14 and 24-32 are not supported at all.

AMR implementation with TCSM3i

The AMR type supporting AMR FR, AMR HR, and EFR is implemented for TCSM3i. Pools 28 and 32 are supported in TCSM3i. The 8 kbit submultiplexing (pool 2, HR only) is not supported in TCSM3i. Pool configuration with Multimedia Gateway (MGW)

The BSC can be directly connected to the transcoder in the MGW using the Ater in MGW feature. As a rule, MGW supports the same pool configuration as the BSC except 8 kbit/s submultiplexing on the Ater interface. Check the detailed pool list in Multimedia Gateway (MGW) Functional Description in MGW documentation. O & M arrangement with TCSM

A LAPD-type 16 kbit/s data channel is dedicated for TCSM fault monitoring and control between the BSC and the TCSM. This channel uses capacity from the TSL1 (bits 1 and 2). Each TCSM has its own LAPD channel towards the BSC. All maintenance operations are carried out over the LAPD channel (supervision and configuration commands). A local user has access to the transcoder site via an interface on the TCSM.

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O & M arrangement with MGW

There is no O & M LAPD link between the BSC and MGW so the BSC does not control the MGW at all. The operator is responsible for creating identical transcoder configurations in both BSC and MGW. TCSM2 capacity

One rack houses 8 pre-installed Transcoder cartridges (TC1C) and 4 Exchange Terminal cartridges (ET1TC). The maximum capacity of a rack is 8 x 120= 960 TCHs in the case of 16 kbit/s submultiplexing, and 8 x 210 = 1680 TCHs in the case of 8 kbit/s submultiplexing. If signalling time slots (TSL16) are not used for speech channels, the maximum capacity is 116 TCHs (16 kbit/s submultiplexing). TCSM3i capacity

One rack in the TCSM3i cabinet consists of six Transcoder cartridges (TC2C). 16 TR3E/A plug-in units are housed in each cartridge. The maximum capacity of a cabinet is 6 x 1920 = 11520 TCHs (ETSI) or 6 x 1520 = 9120 TCHs (ANSI).

3.2

TCSM3i versus TCSM2 The major differences between the TCSM3i and TCSM2 are: .

.

.

TCSM3i has 12 times more capacity compared to current TCSM2 implementation. Redesigned hardware makes TCSM3i more compact. Instead of several plug-in units, one transcoder based on TCSM3i hardware technology consists of one plug-in unit.

.

TCSM3i allows more flexible pool usage in A-interface.

.

TCSM3i does not support 8 kbits/s submultiplexing on the Ater interface.

When the traffic capacity of a TCSM2 is dimensioned to a low value, transmission capacity may be saved. This requires that unused time slots of existing BSC-TCSM highways are multiplexed by an external cross-connect device. One option is to use DN2 equipment, as illustrated in section Digital node equipment DN2.

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TC configuration

For an overview, see BSS transmission.

3.3

TCSM3i versus TCSM3i for combined BSC3i/ TCSM3i installation The major differences between the TCSM3i and TCSM3i for combined BSC3i/ TCSM3i installation are: .

.

3.4

it is possible to use optical STM-1/OC-3 interface in combined BSC3i/ TCSM3i installation in combined installation the transcoding capacity of a TCSM3i can be shared by up to 96 BSCs (ETSI) or 24 BSCs (ANSI)

TCSM versus transcoder in MGW The major differences between using the TCSM and the transcoder in the MGW are: .

.

.

.

.

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MGW and TCSM3i do not support 8 kbit/s submultiplexing on the Ater interface, but TCSM2 does. MGW does not support the same pool set as the BSC. Since there is no O & M link between the BSC and MGW, the transcoding alarms have to be monitored and software changes performed in the MGW. Furthermore, BSC-originated routine testing and diagnostics cannot be used with MGW. Exactly the same pool configuration is created to the BSC and MGW separately. No transcoding related hardware has to be created in the BSC.

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BTS configuration

4

BTS configuration The BTS transmission subsystem is used in the BTS as an interface to the Abis links towards the BSC. FC and FXC units are used in the Nokia UltraSite and MetroSite BTSs, and FIEA, FIPA and FIFA plug-in units in Nokia Flexi EDGE BTS. Nokia MetroSite, Nokia Flexi EDGE and UltraSite support both full rate (FR) and half rate (HR) speech coding. As the TRX supports both FR and HR framing at the same time, call by call (dual mode operation), a given bit pair in the Abis trunk can either form two HR speech channels or a single FR speech channel. AMR codecs are supported by different Nokia base station generations as follows: .

.

Nokia MetroSite, Nokia Flexi EDGE and UltraSite base stations have full AMR support. Nokia Talk-family BTS has AMR support for FR modes 4.75, 5.9, 7.4 and 12.2 as well as for HR modes 4.75, 5.9 and 7.4; with this approach, the link adaptation between full scale of FR modes and almost full scale of HR can be achieved.

.

Nokia 2nd generation DE21 BTS does not support AMR.

.

Nokia InSite BTS does not support AMR.

For a description of the Nokia MetroSite, Nokia UltraSite, and Nokia Flexi EDGE base station, see the following product descriptions: .

.

.

DN9812391 Issue 12-0 en

Nokia MetroSite EDGE BTS, in Nokia MetroSite EDGE BTS Product Documentation. UltraSite EDGE BTS Product Description in Nokia UltraSite EDGE BTS Product Documentation. Flexi EDGE BTS Product Description in Nokia Flexi EDGE BTS Product Documentation

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Logical BTS configurations

There is no limitation for sector configurations in the Nokia MetroSite base station, because each transceiver has an antenna of its own. For diversity, however, more than one TRX is needed per sector. Dual band BTS configuration

This configuration allows you to use GSM/EDGE 900/1800, 800/1800 and, 800/ 1900 TRX combinations in the same cabinet. The BCF function is common to both bands. The site architecture allows separate or combined TRX configurations. The limitations concerning different logical BTSs under the same BCF are also valid for dual band operation. Combined BCF and TRX functions

The TRX can be configured as a master or as a slave. The master TRX handles both O & M functions and Abis interface functions. Chained BTSs

The Nokia MetroSite can be concatenated by an extension kit, which contains D bus and synchronising the frame clock between BTSs. Each extension cabinet saves you the cost of one FC or FXC unit. The O & M functionality is centralised to the master cabinet. You need only one extension cable between cabinets. The maximum number of combined Nokia MetroSite BTSs is 3, and the total length of bus cable is limited to five metres. The TRX addresses are sequentially numbered and configured automatically via an extension cable. The cells can be shared between cabinets to allow flexible upgrading from, for example, 2 + 2 TRXs to 4 + 4 TRXs. Only the FXC transmission card can be used with chained MetroSite EDGE BTS configuration. Dynamic Abis

Dynamic Abis allocation is a solution for higher data rates of EGPRS to ensure cost-efficient and flexible Abis transmission capacity addition. The Dynamic Abis functionality allocates Abis transmission capacity to cells when needed instead of reserving a full fixed transmission link per TRX.

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BTS configuration

As data rates can vary between 8.8 and 59.2 kbps per radio time slot, traditional static Abis allocation does not use transmission resources efficiently. Dynamic Abis uses the existing Abis more efficiently by splitting PCMs into permanent time slots for signalling and a dynamic pool for data. The pool can be shared by a number of transceivers. The Dynamic Abis transmission solution saves a lot in the Abis transmission expansion cost as it allows Abis dimensioning to be performed near the average data rates instead of peak rates. This also applies to the number of 2M BSC interfaces needed. Dynamic Abis interworking .

(E)GPRS (E)GPRS territory method and EGPRS use the Dynamic Abis.

.

Compatibility with base stations Dynamic Abis is compatible with Nokia MetroSite, UltraSite EDGE, and Nokia Flexi EDGE base station EDGE TRXs.

4.1

TRU transmission unit descriptions The Transmission Unit (TRU) is a group of different units making it possible to build various kinds of network topologies with different types of electrical interfaces and transmission media. These boards are located in the Common Unit subrack of the Nokia Talk-family BTSs or in Nokia PrimeSite BTS cabinets. Either one or two slots for TRU units are reserved in the Common Unit subrack of the Nokia Talk-family BTS, and one in the Nokia PrimeSite BTS.

Table 5.

The transmission units in the Nokia Talk-family and Nokia PrimeSite BTSs ETSI

ANSI

PCM (E1)

PCM (T1)

Talk-family

TRUA

TRUE

PrimeSite

TRUB

TRUF

Generally, the Nokia PrimeSite BTS transmission unit differs from the corresponding Nokia Talk-family device in that it does not include the front panel, LEDs, and measurement points. Any other differences in the features will be mentioned in the text below.

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TRUA/B

The TRUA/B is intended for all kinds of BTS E1 PCM networks (2 Mbit/s). The TRUA/B has three 2 Mbit/s interfaces which can be installed for both types of line impedance (75 ohm or 120 ohm) by jumper settings individually. The drop/insert function where selected time slots are branched to the BTS can be executed at the 8 kbit/s level. Other time slots are connected automatically straight through between interfaces one and two. Repeater function in the BTS

The Nokia Talk-family BTS can be a part of a line repeater chain without any external line repeater. Two of the BTS Abis interfaces can tolerate 20 dB attenuation. The maximum distance between these Abis interfaces and the next line repeater depends on the cable type used. A usual distance with symmetrical cables is about one kilometre. Distances greater than that can be achieved by placing a line repeater in line within one kilometre from the BTS site. If only one unit is installed, the third Abis connection in the BTS can tolerate 6 dB attenuation and it has a maximum range of 300 metres. If two transmission units are installed, the BTS has four external 20 dB Abis interfaces. Signal bypass repeater functions in the BTS

When a sustained power failure takes place in a Nokia Talk-family BTS, it is necessary to maintain transmission to other pieces of BTS equipment in the multidrop configuration. This is possible if a terminal repeater, for example, DL2E, is fitted in front of the first BTS in the network. The terminal repeater generates the current needed in the BTS for the signal regeneration. The need for additional line repeaters depends on the distance between the BTS and the terminal repeater. The bypass function is possible for two 2 Mbit/s interfaces (IF1 and IF2) with twisted pair connections of 120 ohm in the transmission unit. During the bypass function, time slots are connected straight through the BTS from the first interface to the second without any cross-connections.

4.1.1

O & M arrangement of transmission The standard control functions of the Nokia equipment are supported. Transmission equipment can be controlled remotely from the network via the Abis interface. The BTS provides a transparent two-way path for remote commands of transmission control and responses.

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BTS configuration

When the transmission equipment is operated locally with a service terminal, the polling of the transmission equipment will automatically be disabled. This operation prevents the generation of unnecessary alarms that would otherwise be sent to the BSC from the Base Control Function Unit (OMU). Transmission equipment can be configured to be polled, that is, managed by BSC or BTS. In BTS polling, the BTS polls its local network elements and nearby sites, for example the microwave radio (repeater). The BTS sends a status inquiry to the polled equipment. The BTS then transmits the collected Q1 information to the BSC through a LAPD link using the OMUSIG channel, usually at a bit rate of 16 kbit/s. The BSC forwards the data to NetAct. In BSC polling, the BSC is the master which collects data from all the Q1 transmission equipment connected to it and then transmits the data to NetAct. The local BTS transmission equipment is configured and controlled via the service terminal or the man-machine interface (MMI). All cabinets have a Nokia-specific external control port (Q1) for the operation and maintenance of the external transmission equipment. Nokia Flexi EDGE BTS offers a Local Management Port (LMP) for the local connection of Element Manager via Ethernet.

4.1.2

Options for transmission Duplicated transmission board (option)

It is possible to use a second, optional transmission board (TRUx) to expand the number of possible transmission links. This option is not available for the Mini BTSs and the Nokia PrimeSite BTS. Integrated radio relay equipment (option)

The BTS is compatible with the Nokia Digital Radio Relay Equipment (DMR1838I). The Nokia Talk-family large-capacity BTSs can be equipped with up to two integrated radio relay equipment models that replace a part of the equipment inside the BTS cabinet and need only the compact microwave heads to be installed externally. The incorporation of the two links makes it possible to build a drop-and-insert microwave relay network for the BTS units when they communicate with the BSC.

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A single piece of radio relay equipment carries up to four 2 Mbit/s Abis links. It is effectively transparent because it offers the same capacity and configuration possibilities as the cabled Abis connections. Any of the 2 Mbit/s signals, or a part of the 2 Mbit/s signals at 8 kbit/s level, can be dropped to the BTS, and the rest of the capacity is available for other BTSs. The frequency range of the radio relay is 18/23/38 GHz. The integrated radio relay equipment is connected to the BTS and the microwave head with two cables. The option is not available for the Mini BTSs. External radio relay equipment (option)

All BTSs are compatible with most of the standard 2 Mbit/s radio relay equipment supplied by different manufacturers. When the external radio relay equipment is used, all the equipment must be fitted externally to the BTS cabinet and cabled to the Abis ports. The BTS cabinets are equipped with terminals to supply external power for the radio transmission equipment. The control is provided through a 9-pin D-connector.

4.2

FC and FXC units The FC and FXC are transmission units for Nokia MetroSite and Nokia UltraSite BTSs. In the Nokia MetroSite BTS, you can house a single FXC unit that provides cross-connection, or a single low-cost FC unit without cross-connection. Nokia UltraSite BTS has slots for up to four FXC units, or one FC unit. In Nokia UltraSite BTS, you should always use an FXC unit for flexible capacity growth. FXC units with cross-connection

The FXC units include a very powerful cross-connection system with a granularity of 8 kbit/s. .

.

.

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FXC E1/T1 (4 x 2M/1.5M), symmetric wire line transmission, 120/100 Ohm FXC E1 (4 x 2M), asymmetric wire line transmission, 75 Ohm FXC RRI (16 x 2M), radio link transmission (Flexbus connection for 2 outdoor units)

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BTS configuration

.

.

FXC STM-1: Unit with 2 STM-1 interfaces for fibre optic cable (L-1.1 laser interface), SDH standard compliant, add/drop and cross-connection at VC-12 layer, synchronisation functions. FXC Bridge: Bridge for the signals between the SDH part of the BTS and the PDH cross-connect of the FXC equipment. Includes Q1 management and cross-connection on 8 kbit/s, 16 kbit/s, 32 kbit/s and 64 kbit/s granularity. This unit is always used with the FXC STM-1 card.

FC units

The FC units were designed to be used with Nokia MetroSite BTS. With Nokia UltraSite BTS, the use of a FXC unit is recommended because of EDGE evolution. Two FC units are available: .

.

FC E1/T1 (1 x 2M/1.5M), wire line transmission (can be used with the Nokia MetroSite BTS and Nokia UltraSite BTS) FC STM-1: a unit with 2 STM-1 interfaces for fibre optic cable (L-1.1 laser interface), SDH standard compliant, add/drop and cross-connection at VC12 layer, synchronisation functions (only to be used with Nokia MetroSite BTS. CXM 4.1 SW or later is required.).

Microwave radio relays

The Nokia UltraSite and Nokia MetroSite base stations can include a radio relayspecific indoor interface unit FXC RRI that can connect one or two radio relay outdoor units to the BTS. All signal connections (n x 2M, Q1) between the BTS and the FXC RRI go through the BTS mother board. Up to two radio outdoor units can be connected to the Nokia MetroSite BTS, and up to eight to the Nokia UltraSite BTS. The power supply of the Nokia MetroSite BTS can support two Nokia MetroHopper or Nokia FlexiHopper radio relay units. The Nokia FlexiHopper radio relay unit supports the capacities 2 x 2, 4 x 2, 8 x 2 and 16 x 2 Mbit/s. The hop lengths can vary between approximately three and 60 kilometres, with the radio frequencies 38 to 13 GHz, respectively. The Nokia MetroHopper radio relay unit's capacity is 4 x 2 Mbit/s and its hop length is up to 1 km. Stand-alone radio relays are interfaced via standard n x 2M and Q1. Power is supplied directly to the radio, not from the BTS.

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Combined O & M and Telecom signalling

With combined O & M and Telecom signalling, you can use the transmission capacity more efficiently. Nokia MetroSite BTS can be configured either as a master or a slave of a BTS. The master TRX handles both the Telecom and O & M functions, which facilitates the combination. The logical links are identified by the Service Access Point Identifier (SAPI). The SAPI values and priorities have been defined in the GSM specification 08.56. In addition, an access channel is defined for the establishment of the O & M link.

Table 6.

4.3

SAPI values and priorities

SAPI 0

Radio signalling procedures

Priority 1

SAPI 62

Operation and maintenance

Priority 2

SAPI 63

L2 management (Access channel)

FIEA, FIPA and FIFA units Flexi EDGE BTS is the future macrocellular EDGE BTS of Nokia BTS portfolio. Flexi EDGE BTS is built from two different modules: the System Module, housing all baseband and transport processing functions as well as BTS O&M, and the Radio Frequency Modules, housing the transceivers and power amplifiers. A transport plug in unit is part of the System Module. The following variants are or will be available: .

FIPA: 8 x E1, T1 balanced 120/100 Ohms

.

FIEA: 8 x E1 coaxial 75 Ohms

.

FIFA: 2 x Nokia Flexbus Interfaces (16x 2 Mbit/s)

To keep the initial roll-out costs low and on the other hand to offer possibilities for future growth, transmission interface units start with basic functionality with two E1/ T1 interface or one Flexbus interface. Further functionality can be easily added later on by additional software licence. The protection of these functionalities will be integrated with the next software releases. The following growth path with advanced features are available by software licence:

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.

additional blocks of two E1/T1s

.

second Flexbus

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BTS configuration

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loop protection (slave)

.

cross-connection and grooming

Nokia Flexi EDGE BTS and the transmission interfaces are managed by the same Element Manager. However, Nokia Flexbus for Nokia Flexihopper and Metrohopper requires an own Element Manager. For an overview, see BSS transmission.

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GPRS and the Gb interface

5

GPRS and the Gb interface The BSC provides Gb interface towards the General Packet Radio Service (GPRS) core network (Serving GPRS Support Node, SGSN). Nokia offers GPRS support in the BSS with powerful radio resource management algorithms, optimised BSS network topology and transmission solutions to ensure optimal investment for operators and high capacity and quality of service for users. The GPRS core network is accessed from the host GSM network via the BSC. This is accomplished by using Packet Control Units (PCU) in the BSC. The Nokia PCU has full support for extensive GPRS radio resource control transactions. This embedded PCU solution provides the most cost-effective solution for the operator. Gb interface is implemented using Frame Relay (FR) or IP connectivity.

5.1

Gb over Frame Relay Frame Relay can be either point-to-point (BSC-SGSN) or there can be a frame relay network located between the BSC and SGSN. The protocol stack comprises BSSGB, NS and L1. Frame Relay as stated in standards will be part of the Network Service (NS) layer. On top of the physical layer in the Gb-interface the direct point-to-point Frame Relay connections or intermediate Frame Relay network can be used. The physical layer is implemented as one or several E1 PCM lines with G.703 interface in ETSI environment or with T1 PCM lines in ANSI environment. The FR network will be comprised of third-party off-theshelf products. The following figures show examples of Gb interface transmission solutions.

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Abis BSC

MSC/SGSN site Transcoders

MSC

BSC

BSC SGSN

Ethernet Switch GGSN #1 GGSN #2

PCM Frame Relay

Gb Interface

Figure 2.

Through-connected channels configured in the transcoders and in the MSC switching matrix

Spare capacity of the Ater and A interfaces is used for the Gb. The Gb timeslots are transparently through-connected in the TCSM and in the MSC. If free capacity exists, it is best to multiplex all Gb traffic to the same physical link to achieve possible transmission savings. In many cases the SGSN will be located in the MSC site and thus this multiplexing has to take place there as well. Normal cross-connect equipment like for example Nokia DN2 can be used for that purpose. The following figure shows how the same can be achieved in a different way, by using additional equipment between the transcoder and the BSC.

Abis BSC

2 Mbit/s PCM Ater + Frame Relay

MSC/SGSN site MUX Transcoders MSC

BSC

BSC Frame Relay

SGSN


Gb Interface

Figure 3.

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GPRS traffic multiplexed on the same physical connection as used for the GSM traffic on the Ater interface

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Another solution is to concentrate GPRS traffic via one network over the Gb interface, with the transmission network providing a point-to-point connection between the BSC and the SGSN.

Abis BSC


MSC

BSC BSC SGSN FR Switch

Ethernet Switch

Packet Data Network (FR, ATM, etc.)

GGSN #1 GGSN #2 FR Switch

Gb Interface

Figure 4.

GPRS traffic concentrated and carried over the Gb interface in a packet data network

Similarly, a Frame Relay network can be used. The Gb interface allows the exchange of signalling information and user data. It also allows many users to be multiplexed over the same physical resources.

Abis BSC


MSC

BSC BSC SGSN PCM links


Frame Relay

Gb Interface

Figure 5.

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GPRS traffic carried over dedicated 2 Mbit/s PCM links

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5.2

Gb over IP The increased demand for packet switched traffic transmission cost efficiency can be met by the deployment of IP in the transmission network. IP can replace Frame Relay networks as the transport medium in the sub-network service layer. Network Service Control Protocol Data Units (PDU) are incapsulated within the UDP datagrams when the IP transport medium is in use. When IP is taken into use, packet-based traffic does not go through the circuit-based Pulse Code Modulation (PCM) network, but IP network instead. The introduction of IP enables to build an efficient transport network for the future IP-based multimedia services, and helps to reduce the transmission costs. The IP transport can be used in parallel with FR under the same BSC and Base Station Controller Signalling Unit (BCSU). One Network Service Entity (NSE) and each PCU always uses either one, IP or FR. Inside one BCSU, separate PCUs can use different transmission media. In the BSC, there is always one local IP endpoint per PCU. Gb over IP supports both dynamic and static configuration. In dynamic configuration, only one IP address and UDP port pair of remote end SGSN is needed to establish NS-VC configuration on Gb. Static configuration can be used, if it is seen feasible to have fixed configuration between BSCs and SGSNs. This might be feasible when the operator has a direct cable connection between the BSC and the SGSN.

Abis BSC


MSC

BSC BSC SGSN

GGSN #1 GGSN #2

Gb over IP

Router

Ethernet Switch

Router

Gb Interface

Figure 6.

5.3

GPRS traffic carried over the Gb interface with IP

GPRS capacity There are two generations of Nokia PCUs:

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.

.

The first generation PCUs are PCU-B in BSC3i and PCU, PCU-S and PCU-T in older BSCs. The second generation PCUs are PCU2-D in BSC3i, and PCU2-U in older BSCs.

The second generation PCU2s are the preferred option and mandatory GPRS CS3 & CS4 application software product. Nokia Packet Control Units are state-of-the-art plug-in units with high capacity and reliability. They control the GPRS radio resources, receive and transmit TRAU frames to the BTSs and Frame Relay packets to the SGSN. High capacity is provided through a state-of-the-art PCU design and with the possibility of future extension. N + 1 redundant PCUs achieve high reliability. The Nokia solution provides full TRX capacity with very high reliability and performance. One PCU is installed into every BCSU for redundancy reasons (N + 1). Additionally there is a possibility to add a second PCU per each BCSU to increase the packet switched capacity in the BSC. In BSC3i, one physical plug-in unit consists of two logical PCUs. The PCU removes the unnecessary TRAU overheads coming from the Abis interface and assembles the data into frame relay for the Gb interface.

Table 7.

Connectivity of logical PCUs

16kbit/s Abis TSL

TRX

Cell/ Segments

BTS

256

256

64

128

256

128

64

64

Logical PCU1

256

128

64

64

(PCU/PCU-S)

(128 RTSL)

Logical PCU2 (PCU2-D/PCU2-U) Logical PCU1 (PCU-B/PCU-T)

Considering the transmission protection it also needs to be decided whether two Frame Relay bearers are needed for each logical PCU using different ETs or if the transmission is protected with cross-connection equipment. It is possible to multiplex more than one Gb interface directly to the SGSN, or multiplex them on the A interface towards the MSC and from there cross-connect them to the SGSN. The PCM carrying the Gb timeslots can be one of the BSC's existing ETs or an ET can be dedicated to the Gb interface.

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BSS redundancy configurations

6

BSS redundancy configurations Depending on availability targets, BSS networks can be designed with redundant transmission paths or equipment. Redundancy switchover is triggered by pilot bits or directly by equipment alarm conditions. As a consequence of availability objectives, it is recommended that at least two TCSM units are equipped per BSS even if the required traffic capacity could be handled by one unit. Yet, in some cases also external redundancy arrangements can be considered as described below. Abis loop with Nokia MetroSite, Nokia UltraSite and Nokia Flexi EDGE base stations

The Abis loop protection is a very effective way to avoid a single faulty transmission link or weather (rain) affecting the cellular network performance. The use of pilot signals for protection switching and MCB & LCB for synchronisation control are applied similarly. For more information, see Radio transmission. The UltraSite integrated transmission node of the FXC units can operate as a loop master station or a slave station. The single FXC unit in a MetroSite can operate as a loop slave. The Flexi EDGE BTS can operate as a loop slave. Radio link hop protection

The hot standby mechanism is a commonly applied system to protect against HW failures of radio outdoor units whenever a chain of BTSs is connected together using radio transmission.

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BSC 1+1 HSB

FIU19E

FXC RRI

BTS

Figu Figure re 7.

Radi Radio o link link hop hop prot protec ectio tion n


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Operation and maintenance of transmission equipment

7

Operation and maintenance of transmission equipment The ability to monitor and control the whole network is one of the most important features for the GSM operator. To facilitate this, all elements of the GSM network, the BSS, the MSC, the HLR and the VLR, are connected to the Nokia NetAct for network monitoring and control. The connection to the Nokia NetAct is made via Q3 interface. For transmission equipment in general, typically fault management and performance management are supported. For TRU, DN2 and DMR, basic G.821 signal quality counters are supported. For Nokia FXC and FC transmission equipment as well as Nokia Flexi EDGE transmission units, the full or partial set of G.826 signal quality counters are supported. Configuration management for FXC and FC transmission equipment is supported by launching an element manager integrated from the Nokia NetAct. The Nokia NetAct management functions include fault management (FM), performance management (PM) and configuration management (CM) of network elements. The BSC can support up to 56 Q1 supervisory channels. Also, a maximum of 1024 separate transmission equipment with Q1 interface can be supervised, including the transmission equipment supervised by the BSC and the BTS. The DN2, TRU, Nokia FXC equipment and Nokia Flexi EDGE transmission units are able to transfer Q1 data between TSL0 and some other time slot within E1 (in many cases TSL31 is used), or to the Q1 overhead channel of a Flexbus signal.

7.1

Supervisory channels BSC

The BSC is connected to the Nokia NetAct with a dedicated X.25 connection, using a trunk time slot for the BSC-MSC-Nokia NetAct path, or a LAN connection using Ethernet. The Nokia NetAct connection can also be duplicated for protection. Direct access to packet network is also available.

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The supervisory channel for BSC-supervised transmission equipment is carried in a PCM time slot. Remote maintenance or control of a piece of transmission equipment can be done with BSC MML commands, or by launching the equipment element managers integrated from the Nokia NetAct. BTS

A BTS is connected via the BSC to the Nokia NetAct. The BTS-BSC path is realised through a LAPD channel and the path BSC-MSC-Nokia NetAct by using an X.25 channel or LAN. The transmission equipment can be connected to BTS supervision in different ways. The connection is an internal Q1 bus connection if the equipment is integrated in the BTS. Remote maintenance or control of a piece of transmission equipment can be done with BSC MML commands or by launching the equipment element managers integrated from the Nokia NetAct. TCSM

For the transcoder's remote supervision and control, one LAPD-type data channel per TCSM is used between the BSC and the TCSM. This channel uses the 16 kbit/s capacity from trunk time slot 1. BSC MML commands are used for supervision and control. The TCSM can be brought into test state and diagnostic tests can be run via the BSC. MGW

Supervisory channels are not supported. Nokia Q1 managed transmission equipment

Nokia Q1 managed transmission equipment, not integrated to a Nokia BTS, is managed remotely via a Q1 management channel. DN2 and MetroHub can pick up the Q1 management channel from the PCM time slot. In some Nokia Q1 managed equipment such as FIU 19 and FIFA, the Q1 management channel must be connected to the equipment via a Flexbus overhead.

7.2

Local O & M BSC

The BSC has two V.24 local user interfaces.

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Operation and maintenance of transmission equipment

BTS

The BTS has a V.24 local user interface. The interface is used for the BTS's own O & M and for the transmission equipment that is under BTS supervision. TCSM2/TCSM3i

A V.24 local user interface is available for eac h TCSM unit in a TCSM2/TCSM3i. Transmission equipment

Most Nokia transmission equipment has a Q1 interface connector. The interface is compatible with Nokia's Transmission Management System (TMS) protocol. The Nokia FXC/FC transmission equipment used with Nokia MetroSite, Nokia UltraSite or Nokia MetroHub, and the FIU 19 support the Nokia Q1 protocol that is an enhancement to the transmission management system (TMS) protocol. The TMS comprises equipment ranging from a hand-held service terminal to a TMSOS work station. In Nokia Flexi EDGE, the Q1 interface is provided by the System Module. It also offers the LMP for the local management of the BTS and integrated transmission. The Nokia Service Terminal is a tool for local configuration and maintenance of the TRU (and any other piece of Nokia transmission equipment). It is normally needed in the installation phase. The Service Terminal emulator is also available as PC software. The DN2 manager is a special package of software for the DN2's local configuration management. It requires a standard PC with Windows. The DN2 manager allows easy and user-friendly configuration of transmission equipment (such as the DN2). It also includes software for service terminal emulation. Also TRU Manager, analogous to the DN2 Manager, is available. For configuration management of the FXC/FC transmission equipment, a suite of element managers is provided. With UltraSite BTS, the element manager is UltraSite BTS Hub Manager. With MetroSite BTS, the transmission card managers are integrated in the BTS manager. With MetroHub, the element manager is MetroHub Manager. For Nokia Flexi EDGE, there is a common Element Manager for the BTS and transmission. However, the FIFA Flexbus unit requires Nokia Hopper Manager.

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7.3

Remote O & M The Nokia NetAct remotely monitors and controls all GSM network elements including the TCSM and transmission equipment. To enable remote configuration and interrogation of the transmission elements involved, NetAct provides the remote use of node managers, remote access via Service Terminal Emulator session, and remote access via MML session. The Transmission Node Management feature in NetAct offers the users access to node managers through a Node Manager Server. As for the GSM OMC, the Nokia NMS is designed for full GSM network monitoring and control including transmission equipment.

Note Note that some network capacity must be reserved for O & M channels.


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8

Requirements on transmission network There are different scenarios for the realisation of the network: 1.

The network is owned by a GSM operator and built along with the GSM BSS. It is possible to tailor the transmission of the network and O & M features exactly for GSM BSS.

2.

The GSM BSS network is built by using the existing transmission network owned by the GSM operator. Old transmission equipment may set restrictions on the network use.

3.

Transmission network capacity is only leased to the GSM operator. The GSM operator may not be allowed to supervise the transmission network directly. The actual network realisation may be unknown.

8.1

2 Mbit/s transmission paths The basic functional requirements on the 2 Mbit/s transmission paths are the following:

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1.

Time slot sequence must be maintained between the TCSM and the BSC and also between the BSC and the BTS.

2.

It is recommended that the entire 2 Mbit/s stream is transparent between the TCSM and the BSC. If n x 64 kbit/s cross-connect devices are used (that is, fractional 2 Mbit/s), individual time slots may go out of service because of faults in certain transmission sections without the BSC, TCSM, or MSC directly detecting it. This fault condition will eventually be detected by failing calls in certain circuits.

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3.

DN2 loop protection prefers TSL0 to be transparent through the whole loop. Loop synchronisation control bits (master clock bit, MCB, and loop control bit, LCB) are normally transmitted using TSL0 bits. The TRUA, FXC/FC and FIxAunits have no restrictions; MCB and LCB can be transmitted in any time slot.

4.

The EGPRS dynamic Abis pool (EDAP) size at the BSC and BTS, the time slot order in the BSC and BTS EDAPs and the EDAP starting time slot in the UltraSite BTS Traffic Manager and the incoming PCM to the BTS must be the same. Because of maintenance reasons, using the same timeslot allocation at the BSC and BTS is recommended. If required, the EDAP starting timeslot at the BSC and the incoming PCM to the BTS can be different. Cross-connections are allowed, but the PCM frame or the n x 64 cross-connection must comply with the G.796 standard to maintain the octet sequence integrity of signals being cross-connected. EDAP and the TRXs tied to it (including traffic/EGPRS master and signalling channels) have to share the same monolithic Abis connection and PCM frames should have octet sequence integrity which can be achieved in two ways: a.

Using 1-3 PCM lines that function according to the G.796 standard. If the BTS capacity requires several PCM lines, a normal network delay variance between the PCM lines does not impact EDGE performance. The EDAP pool and the TRXs tied to it have to be located on a single PCM.

b.

Using fractional E1, n x 64 k connection that complies with the G.796 standard. This means that this n x 64 k cross-connection block is handled with a single cross-connection command at every transmission node. This means that the EDAP pool and the TRXs tied to it must have a connection made with a single monolithic PCM or a single monolithic n x 64 k connection which comply to the octet sequence integrity of the G.796 standard. This structure needs to be maintained throughout the network. In case the PCM line does not fulfil the octet sequence integrity requirement as specified in ITU-T G.796, a maximum of +/- three PCM frame delay between time slots is tolerated when the BSC SW S10.5 ED CD1.2 or newer release is being used. For more information on Dynamic Abis dimensioning, see Abis EDGE Dimensioning in GSM/EDGE BSS System Documentation Set.

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All E1 type interfaces conform to the ITU-T Recommendations G.703 and G.704 and the T1 interfaces conform to T1.403. All PCM interfaces are of repeater type, with no power feeding from the interface.

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8.2

Synchronisation of BSS network The accuracy requirement for the primary reference clock (PRC), which is the master clock source of the whole network, is given in the ITU-T recommendation G.811. PRC equals the so-called Stratum 1 level clock and the requirement for the maximum long-term frequency departure of PRC is 1 x 10-11. In live networks, the network timing is affected by jitter/wander, but when the synchronisation of the network is correct, the same basic accuracy exists all over the network when metered over a long period. The synchronisation of the entire network should be constructed so that the synchronisation delivery to all over the network is hierarchical (leveling). This reduces the possibility for the synchronisation to be corrupted. Even though most of the jitter is filtered when passing through transmission nodes (because of jitter transfer function), wander accumulates in synchronisation distribution chains; the limits for network jitter/wander are set in G.823. The BSC clock system (CL3TG) is a Stratum level 3 synchronisation source, which works slaved to the traffic trunks or from external synchronisation source. Its control range is +/- 15 x 10 exp -6 and pull-in range +/- 2 x 10 exp -6. Accuracy of automatic control is 5 x 10 exp -10. If traffic trunks/external sources are deemed invalid, the clock enters plesiochronous operation. CL1TG has the same characteristics, but external synchronisation sources are not possible. The BTS clock system can be divided into two independent parts, transmission node part and BTS internal. The clock of the transmission part is in Phase Locked Loop (PLL) to the incoming 2M signal (selectable to be synchronised to one of the 2 Mbit/s Abis signal(s) or 2MHz synchronisation input, according to the priority list). This transmission part clock is used for timing the outgoing data of all the 2Mbit/s interfaces, including the one towards the other units of BTS. The principle is that in the mobile network the synchronisation goes from MSC to BSC to BTS. However, in reality that synchronisation chain might be broken somewhere and, for example when using leased lines, the BTS may take the reference synchronisation from the transmission network of another operator. This does not harm the system if also that transmission synchronisation is originated from PRC and it is accurate enough; if occasional data slips occur, the mobile network system can tolerate it. The same 1 x 10-11 long-term accuracy should exist all over the network if the network synchronisation is correct, only jitter/wander instability should exist. The long-term Abis interface accuracy requirement for Nokia BTSs is ± 0.015 ppm or better (1.5 x 10-8), which is 1500 times more loose than the PRC requirement. The GSM specification for the BTS Air interface accuracy is ± 0.05 ppm, which can be attained easily even with the worst case situation inside the BTS (RF part inaccuracy), if the Abis accuracy is ± 0.015 ppm.

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Because the Abis reference signal contains jitter/wander, it cannot be used directly for timing the BTS air interface. The jitter/wander instability must be filtered away before that. Therefore the BTS master clock (OCXO) is not in a phase-locked loop (PLL) to the incoming Abis signal coming from the transmission part, but it is using the Abis signal as a reference for 'calibrating' the BTS master clock periodically. There is a several-layer averaging algorithm which takes care of controlling the OCXO frequency and also of filtering away the effects of transmission jitter/wander. Therefore, in practise the BTS runs fully under its own OCXO. The OCXO frequency is only adjusted automatically towards the 2M reference. This does not mean it is moved sharply to the point the adjustment calculations show, but there is a limit in the algorithm for the maximum frequency step in order to improve stability, that is, to reduce wander effects. In case of synchronisation fault there are two cases for BTS operation: .

.

If BTS O & M signalling is cut, BTS OCXO starts an independent operation (free run) and takes no reference from the Abis interface. Then the mistuning towards the faulty reference is avoided and the air interface frequency is in most cases correct immediately after the O & M recovery. O & M signalling exists but the synchronisation reference is not correct. In this case the OCXO frequency will slowly start to drift towards the faulty synchronisation. Because the maximum adjustment step is limited, it may take several hours for the BTS to exceed the GSM specifications in the air interface

Note An alarm ('Difference in frequencies between the PCM and BTS master clock') is raised when the BTS clock unit notices a difference between the incoming 2M reference and the internal OCXO frequency - the difference limit for the alarm activation is 0.1 ppm. This means the synchronisation disruption is noticed at the BSC.

Then, if the BSC does not get a proper synchronisation reference, it leads in the long run to the situation that the BSC cannot feed BTSs with a reference which is accurate enough (0.015 ppm). The effect on BTSs is explained above.

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8.3

Transmission delay of BSS network Round trip delay refers to the amount of the time it takes for an electrical signal to travel from one end of a transmission medium to the other end and back. The 3GPP TR 03.05 defines a maximum of 188.5 ms for a round trip delay from the A interface to the mobile station and back. The transcoder (TC) encoder/ decoder loop alone requires about 30 ms. Taking all delay contributions into account leaves approximately 6 ms for pure BSS transmission delay. This corresponds to about 1000 km of cable transmission equipment. The TC and the BTS framing unit together form a control loop for adjusting the transcoding and rate adaptation unit (TRAU) frame phase for a minimum delay. The stable operation of this controller requires that the transmission delay between the TC and the BTS is less than 40 ms. This forms the upper limit to the delay. A satellite circuit will nominally cause a delay of 260 ms. Therefore satellite circuits cannot be directly tolerated in a BSS network between the TC and the BTS. On the other hand, satellite circuits between the TC (for example a TC located at the BSC site) and the MSC are acceptable despite the added delay. Satellite Abis or Ater circuits can be used as options. This requires certain system level changes and the whole BSS has to be reserved for satellite use. According to the ITU-T Recommendation G.114, the delay should be kept under 400 ms and echo cancellers should be used. When using satellite circuits, this value is exceeded. Other GSM network-related traffic, such as signalling, accounting and O & M, can be transmitted through satellite circuits with due case by case consideration of delay. Channel throughput may suffer because of the protocol used. In the case that acoustic echo cancellation (to cancel echo in the loop BSS - MS BSS) is activated in the TCSM, its performance will degrade if the one-way delay between TCSM and BTS is more than 5 ms.

8.4

Error rate performance of BSS network In the BSS network the speech signal is transmitted at a speed of 16 kbit/s using FR transcoding, and at 8 kbit/s using half rate (HR). The transcoded signal has less bit redundancy than a normal PCM but still its robustness against transmission bit errors is good.

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Speech quality is good if the ITU-T Recommendation G.821 performance objectives are met. If this is the case, fewer than 10% of one-minute intervals have a BER value higher than 10E-6, fewer than 0.2% of one-second intervals have a BER value higher than 10E-3, and fewer than 8% of one-second intervals have any errors. For digital transmission links with a data rate of 1.5 Mbit/s and higher performance statistics and objectives according to ITU-T Recommendation G.826 are applicable. The G.826 performance objectives are more stringent than G.821, which means meeting those will result in good speech quality, too. The performance measurement is block error based with G.826, in difference to the bit error based measurement with G.821. The ESR and SESR values gained by performance measurement from both standards can be approximated to each other, but are as result not the same.

Note At BER=10E-3 most transmission equipment starts sending 2M AIS (alarm indication signals). EDGE applications are more sensitive to degraded BER than GSM voice.

GSM signalling channels are robust to errors because of the protocol used.

8.5

Slips in transmission Slips in the transmission equipment are caused by synchronisation problems. A 2M trunk signal frame (controlled) slip will affect two consecutive FR TRAU frame bits in roughly the same way as bit errors. Even modest slip rate requirements, 30 slips/hour, will result in rare background clicks only. Trunk circuits conforming to the ITU-T Recommendation G.822 perform well. Usually there are practically no slips as BSS network synchronisation is hierarchic. If faults occur, PCM signal frequencies in stand-by trunks may differ by up to 50 ppm, resulting in a slip in two seconds. GSM signalling channels are robust to slips because of the protocol used.

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8.6

Echo control in BSS As internal delays are noticeable in the GSM system, echo cancelling devices are included at the MSC-PSTN interface to cancel any echoes resulting from PSTN network 4/2 wire hybrids. Problems may arise if additional echo controllers (satellite circuit echo controllers, acoustic echo controllers and so on) are tandem connected with GSM echo cancellers. Besides slips, also clock frequency differences cause convergence problems to echo cancellers. The TCSM includes an acoustic echo cancellation function that removes the acoustic echo generated in the MS.

8.7

Jitter and wander prevention in BSS Excessive jitter and wander will stress equipment clock recovery and buffer circuitry, causing errors and slips. It is also possible that jitter and wander accumulate in long transmission chains. The GSM equipment is designed to meet the requirements of the ITU-T Recommendation G.823 as regards the maximum input jitter from the PCM line. In network nodes (such as the BSC), the jitter transfer function is designed to prevent jitter accumulation. If a 2 Mbit/s signal from the BSC used for BTS synchronisation is carried transparent via a SDH network where the SDH network is not synchronised to the BSC, the 2 Mbit/s line may have abrupt frequency deviations (pointer jitter) even if data is transmitted without problems on the line. The BSC and BTS are designed to tolerate these deviations. If a line used for synchronisation extraction for the BSC experiences these deviations, the BSC frequency may start to fluctuate. However, this fluctuation will not typically mistune the frequency of the BTSs considerably, since the BTS has a long averaging time. Otherwise if the fluctuation frequency is low, the amplitude of fluctuation is also low. For an overview, see BSS transmission.

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9


MSC

BSC

DN2/ MetroHub

MetroHub

Tellabs or 3rd party DXX

BTS integrated cross-connection function BTS integrated transmission terminal function

Figure 8.

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Interconnection of different networks

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9.1

Digital node equipment DN2 The Digital Node equipment DN2 is a general-purpose transmission crossconnect and multiplexing device. For details of the DN2, see the appropriate handbooks, such as DN2 Operating Handbook. Applications in GSM BSS

The DN2 equipment is normally used to save transmission costs by packing the 2 Mbit/s channels more effectively. Application examples are shown in Figure 9 Multiplexing of the BSS and external channels with the DN2. It is possible to multiplex other services on a transmission link (to use the otherwise unused capacity). Another important application area is redundancy. Some examples are given in the sections discussing redundancy. The DN2 is normally supervised by the BSC. Mechanically the DN2 comprises one (or two, if expanded) 19-inch subrack. A fully equipped NDM 19 in Subrack has 16 board slots (+ one for the power unit): .

A bus power unit BPU (or EBPU if expanded DN2) requires one slot.

.

A control unit CU requires one slot.

.

.

Dual 2M interface units IU2 require one slot. The number of IU2s is 1 - 13 (or the number of 2M interfaces 2 - 26). A power supply unit NDU (NDM DC Unit), NAU (NDM AC/DC Unit) or NDA (NDM DC Adapter); the right-hand board slot is wide and reserved for power supply units

When the DN2 is supervised by the BSC, the maximum number of usable 2 Mbit/ s interfaces in a DN2 subrack is 24. With two subracks, the maximum is 38 interfaces. The Q1 supervision bus from the BSC to the DN2 uses a loop-back crossconnection set-up in the DN2 (to change Q1 from TSL31 over to TSL0, requiring one IU2 board). It is also possible to form the TSL31/0 loop between the CU and one of the IU2 interfaces. This will save one IU2 interface.

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BTS1

BSC

DN2

2 Mbit/s G.703

DN2

BTS2

by-pass traffic

by-pass traffic

Figure 9.

Multiplexing of the BSS and external channels with the DN2

Note By-pass traffic may also flow through the BSC to the MSC.


9.2

MetroHub transmission node Nokia MetroHub transmission node is an outdoor capable stand-alone crossconnect, which is developed especially to support radio link based BSS transport networks. Its main traffic protection feature is the loop protection. MetroHub provides a flexible, expandable and cost-effective solution for the purposes required by a GSM/EDGE operator. The maximum cross-connection capacity of the MetroHub is 56 x 2 Mbit/s with a switching granularity of 8 kbit/s. With MetroHub, the same FXC units can be used as with integrated UltraSite BTS transmission. Therefore E1, T1, Flexbus and STM-1 interfaces can be integrated to MetroHub.

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BSC n x E1

Protected loop

BTS Nokia MetroHub

Figure 10.

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Network principle

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Nokia MetroHub grooms the traffic from several base stations. Partially filled connections are thus combined and trunk efficiency increased. To ensure transmission availability, the Nokia PDH loop protection concept and SDH ring protection are supported. For more information on PDH loop protection, see Nokia PDH loop protection in GSM networks (the document can be obtained upon request from your Nokia representative).

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BSC-BTS transmission examples

10

BSC-BTS transmission examples The following examples are intended to give you a more practical view of network design.

10.1

Overview of transmission network Figure 11 BSS network using leased lines presents a BSS network that is mainly based on using leased lines. Even in a case such as this, some lines (BTS2-BTS3) are directly owned and controlled by the GSM operator. The GSM operator has only a limited supervision and control access to the main transmission network.

Nokia NetAct PSTN

MSC TC

BTS4

Transmission network from where capacity can be leased (e.g. PSTN) BTS3

DN2

BSC

BTS2 BTS1

BTS chain

by-pass traffic

Figure 11.

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BSS network using leased lines

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10.2

Point-to-point transmission The most common and straightforward transmission configuration is the point-to point connection between the BSC and all the BTSs. Figure 12 Point-to-point connection between BSC and BTS presents an example of this type of connection. Only one TRU unit is required.

3 2 1 FC/FXC/ FIxA

BTS

BSC 3 2 1 FC/FXC/ FIxA

BTS

Figure 12.

10.3

Point-to-point connection between BSC and BTS

Multidrop chain transmission The multidrop chain (see Figure 13 Multidrop chain ) is an important network configuration, especially when new services are covered. The advantage of the chain is that many low-capacity stations can be tied to a single 2M PCM line. GSM service area often suggests this kind of approach. As with point-to-point connections, the transmission media selection is unrestricted.

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BSC

Figure 13.

10.4

3 2 1 FC/FXC/ FIxA

3 2 1 FC/FXC/ FIxA

3 2 1 FC/FXC/ FIxA

BTS

BTS

BTS

Multidrop chain

Loop transmission A point-to-point connection can be duplicated to look like a loop and a multidrop chain can be looped back to increase circuit availability, as shown in Figure 14 Duplicated point-to-point and multidrop loop.

3 2 1 FC/FXC/ FIxA

BTS

DN2

BSC

1

Figure 14.

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3

2

1

3

2

FC/FXC/ FIxA

FC/FXC/ FIxA

BTS

BTS

Duplicated point-to-point and multidrop loop

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10.5

Radio transmission The radio relays provide a fast method of building networks, as Figure 15 Loop, radio relay transmission network indicates. If needed, radio relays can be replaced by fibre, especially when the station capacity later grows.

BSC

Metro Hub

BTS

BTS

FXC RRI

FXC RRI

FXC RRI

FXC RRI

FXC RRI

FXC RRI

BTS

BTS

BTS

I R R C X F

Figure 15.

10.6

BTS

Loop, radio relay transmission network

DN2 in the MSC-BSC path The DN2 is usually located in the MSC site. The DN2 is required at both ends of the MSC - BSC path as the time slot allocation is not standard. In this application the SM2M multiplexing function can be replaced by the DN2, and at the same time the DN2 can multiplex some by-pass traffic.

Note Since the DN2 makes connections at the timeslot or sub-timeslot level, it is not able to pass trunk fault situations end-to-end, and the MSC and BSC may be unaware of unavailable time slots. Because of this, this configuration can be recommended for temporary use only. This restriction applies to configurations presented in Figures Example use of the DN2 and Introduction of the TCSM2 without a dedicated transmission link.

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1 + 1 protection can be used in the transmission path between the DN2s. Figure 16 Example use of the DN2 presents an example use of the DN2.

BSC1

BSC4

BS C 2

DN2

DN2

Nx TC

MSC

BSC3 by-pass traffic

Figure Figure 16.

10.7 0.7

Example Example use of the DN2

Noki Nokia a Ultr ltraSit aSite e netw networ ork k examp xamplle The UltraSite network can implement the Abis loop protection or simpler star or chain network topology. Figure 17 Example 17 Example of a Nokia UltraSite network shows network shows a HSB protected link. With UltraSite BTS and FXC/FC units as well as Flexi EDGE BTS and FIFA, the same transmission topologies as with Talk BTS/TRUA units are supported. With UltraSite BTS, the maximum possible number of transmission interfaces and capacity is enhanced.

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Dir 1

FB2

BSC ET

E1

FIU IF1 19

FB1

FB1

FlexiHopper

MetroHub

FlexiHopper

UltraSite or Flexi EDGE

FB2

FB3 FlexiHopper

FlexiHopper Dir 2

Figure Figure 17. 17.

Exampl Example e of a Nokia Nokia Ultra UltraSite Site netwo network rk


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11

Time slot allocations in BSS The TCSM has the capability to support different time slot allocations on the Ater interface. Figure 18 Time slot allocation for 16 kbit/s bit rate channels (typically full rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface with the TCSM2/TCSM3i shows the 16 kbit/s allocation and Figure 19 Time slot allocation for half rate traffic with 8 kbit/s TRAU frames on the Ater 2 Mbit/s interface with the TCSM2 shows the 8 kbit/s allocation. In addition to these, it is possible to configure a combination of 16 kbit/s and 8 kbit/s portions of time slots. For the HSCSD service capacity, units of 16 kbit/s, 32 kbit/s and 64 kbit/s are allocated. It is also possible to combine HSCSD channels with FR/EFR and HR channels (as well as AMR with TCSM3i) on a common Ater interface. Signalling channels between the BSC and the MSC, and sometimes OMC channels, are carried by entire 64 kbit/s time slots. They lower the maximum number of traffic channels, especially in the case of 16 kbit/s allocation. TSL0 carries normal ITU-T type framing overhead information (synchronisation, alarms and trunk line performance). Figure 18 Time slot allocation for 16 kbit/s bit rate channels (typically full rate, enhanced full rate or AMR ) on the Ater 2 Mbit/s interface with the TCSM2/ TCSM3i illustrates the Ater time slot allocation for 16 kbit/s bit rate channels (typically full rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface with the TCSM2/TCSM3i. 64 kbit/s channels that must be through-connected between the BSC and MSC are not shown explicitly in this figure; the TCSM2/TCSM3i allows any time slot to be through-connected. Typically, for example, time slot 31 could be used for that purpose, in which case the traffic channels 24 - 27 would be left out. Figure 20 Ater time slot allocation example for the HSCSD application: a combination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/s channels (HS4) shows an example of Ater allocation for HSCSD. Channels of different capacities can be combined at the Ater interface. Each A-PCM may be allocated a certain (single) type of channels. In TCSM2, the channels are A, B, C, D, E, or F, whereas in TCSM3i they are G, H, or I (see Table 3 Circuit types of TCSM2 and TCSM3i). TCSM3i). Thus it is also possible to share a common Ater line between HSCSD

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channels and 16 kbit/s submultiplexed channels (FR/EFR speech, FR data, nonHSCSD data, and, with TCSM3i, also AMR). Figure 21 Time slot allocation of 2 x 16 kbit/s channels of Figure A-PCM1 on A interface shows how the channels appear at the A interface. Unused bits are marked with x in the figures.

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BIT TSL 0 1

2

3 4 5 6 7 8 9

10 11

12 13 14 15 16 17 18 19 20 21

22 23 24 25 26 27 28 29 30 31

1

LAPD TCH.4 TCH.8 TCH.12 TCH.16 TCH.20 TCH.24 TCH.28 x TCH.4 TCH.8 TCH.12 TCH.16 TCH.20 TCH.24 TCH.28 x TCH.4 TCH.8 TCH.12 TCH.16 TCH.20 TCH.24 TCH.28 x TCH.4 TCH.8 TCH.12 TCH.16 TCH.20 TCH.24

Figure 18.

DN9812391 Issue 12-0 en

2

3

4

5

6

LINK MANAGEMENT TCH.1 TCH.2 TCH.5 TCH.6 TCH.9 TCH.10 TCH.13 TCH.14 TCH.17 TCH.18 TCH.22 TCH.21 TCH.25 TCH.26 TCH.29 TCH.30 TCH.1 TCH.2 TCH.5 TCH.6 TCH.10 TCH.9 TCH.13 TCH.14 TCH.17 TCH.18 TCH.22 TCH.21 TCH.25 TCH.26 TCH.29 TCH.30 TCH.1 TCH.2 TCH.5 TCH.6 TCH.9 TCH.10 TCH.13 TCH.14 TCH.17 TCH.18 TCH.22 TCH.21 TCH.25 TCH.26 TCH.29 TCH.30 TCH.2 TCH.1 TCH.5 TCH.6 TCH.9 TCH.10 TCH.13 TCH.14 TCH.17 TCH.18 TCH.22 TCH.21 TCH.25 TCH.26

7

8

TCH.3 TCH.7

TC_PCM 1

TCH.11 TCH.15 TCH.19

TCH.23 TCH.27 TCH.31 TCH.3

TC_PCM 2

TCH.7 TCH.11 TCH.15 TCH.19 TCH.23 TCH.27 TCH.31 TCH.3

TC_PCM 3

TCH.7 TCH.11 TCH.15 TCH.19 TCH.23 TCH.27 TCH.31 TCH.3

TC_PCM 4

TCH.7 TCH.11 TCH.15 TCH.19 TCH.23 TCH.27

Time slot allocation for 16 kbit/s bit rate channels (typically full rate, enhanced full rate or AMR) on the Ater 2 Mbit/s interface with the TCSM2/TCSM3i

# Nokia Corporation

75 (92)


BIT TSL 0 1

2 3 4 5 6 7 8 9

10 11

12

13 14 15 16 17 18 19 20 21

22 23

24 25 26 27 28 29 30

1

3

4

5

6

7

8

LINK MANAGEMENT LAPD 2 5 1 3 4 6 7 8 9 10 13 14 12 11 15 21 17 18 19 20 23 22 25 28 31 24 26 27 29 30 x 1 2 3 4 5 6 8 10 13 14 11 7 9 12 15 18 21 17 19 20 23 22 24 25 26 27 28 29 30 31 x 5 1 2 3 4 6 11 7 8 9 10 13 14 12 15 17 18 19 20 23 21 22 25 31 24 26 27 28 29 30 x 5 1 2 3 4 6 10 13 14 11 7 8 9 12 15 17 18 19 20 23 21 22 24 25 26 27 28 29 30 31 x 1 2 3 4 5 6 7 8 9 10 13 14 12 11 15 17 18 19 20 23 22 21 24 25 26 27 28 29 30 31 x 1 2 3 4 5 6 7 8 9 10 13 14 12 11 15 17 18 19 20 23 22 21 24 25 26 27 28 29 30 31 x 1 2 3 4 5 6 11 7 8 9 10 13 14 12 21 15 17 18 19 20 23 22 25 28 31 24 26 27 29 30 #7 signalling / Nokia NetAct connection #7 signalling / Nokia NetAct connection

31

Figure 19.

76 (92)

2

TC_PCM

1

TC_PCM 2

TC_PCM 3

TC_PCM 4

TC_PCM 5

TC_PCM 6

TC_PCM 7

#7 signalling / Nokia NetAct connection

Time slot allocation for half rate traffic with 8 kbit/s TRAU frames on the Ater 2 Mbit/s interface with the TCSM2

# Nokia Corporation

DN9812391 Issue 12-0 en


Note The numbers in the cells refer to the number of traffic channels within a PCM trunk.

DN9812391 Issue 12-0 en

# Nokia Corporation

77 (92)


BIT TSL 0 1

2 3 4 5 6 7 8 9 10

1

LAPD

12 13 14 15 16

17

HS4.1

18 19 20

HS4.2 HS4.3 HS4.4 HS4.5 HS4.6 HS4.7 HS4.8 HS4.9 HS4.10 HS4.11 HS4.12 HS4.13 HS4.14 HS4.15

21

22 23 24 25 26 27 28 29 30 31

3

4

5

6

7

8

LINK MANAGEMENT

HS2.2 HS2.4 HS2.6 HS2.8 HS2.10 HS2.12 HS2.14 HS2.16 HS2.18 HS2.20 HS2.22 HS2.24 HS2.26 HS2.28 HS2.30

11

Figure 20.

78 (92)

2

X

HS2.1

TC_PCM 1 (HS2)

HS2.3 HS2.5 HS2.7 HS2.9 HS2.11 HS2.13 HS2.15 HS2.17 HS2.19 HS2.21 HS2.23 HS2.25 HS2.27 HS2.29 HS2.31 TC_PCM 2 (HS4)

Ater time slot allocation example for the HSCSD application: a combination of 2 x 16 kbit/s channels (HS2) and 4 x 16 kbit/s channels (HS4)

# Nokia Corporation

DN9812391 Issue 12-0 en


BIT TSL 0 1

2 3 4 5...28 29

30 31

Figure 21.

BIT TSL 0

1

HS2.3 HS2.4 ... HS.29 HS.30 HS.31

1

5

6

7

8

x x x

2

3

4

5

6

7

8

LINK MANAGEMENT

2

HS4.2 HS4.3 HS4.4

14 15 16 17 18

4

Time slot allocation of 2 x 16 kbit/s channels of Figure 20 A-PCM1 on A interface

HS4.1

4 5...13

3

LINK MANAGEMENT x x x x

HS2.1 HS2.2

1

3

2

...

HS4.14 HS4.15 X X X

... 31

Figure 22.

DN9812391 Issue 12-0 en

Time slot allocation of 4 x 16 kbit/s channels of Figure 20 A-PCM2 on A interface

# Nokia Corporation

79 (92)


11.1

Time slot allocation in combined BSC3i/TCSM3i installation (ANSI) In combined BSC3i/TCSM3i installation, the transcoding capacity of a TCSM3i can be shared by the master BSC, installed together with the TCSM3i, and one or more remote BSCs that are connected to the master BSC. The Ater interface between the master BSC and TCSM3i is internal and always based on ETSI PCM with 32 timeslots and it is therefore able to carry five ANSI T1 TC-PCMs. Since the external PCMs carry only 24 timeslots in ANSI environment, the group switch capacity of the master BSC is therefore not effectively used, unless a fifth TC-PCM is connected to a TR3E plug-in unit and submultiplexed into the free space on the Ater PCM. This extra PCM cable is called BRANCH PCM. The following figures describe how the MAIN PCM and BRANCH PCM are submultiplexed into the Ater PCM between the master BSC and TCSM3i with different data rates. Note that timeslot 31 on the Ater PCM cannot be used for through-connection. Branch PCM

Main PCM LAPD

1..6

TC_PCM 1

1..6

TC_PCM 2

LAPD

1..6

TCH 1-24

TCH 1-24

7..12

TC_PCM 5

Ater PCM

7..12

TCH 1-24

7..12

TCH 1-24

13..18

TC_PCM 2 TCH 1-24

TC_PCM 3

13..18

13..18

TCH 1-24

19..24

TC_PCM 1

TC_PCM 4

TC_PCM 3 TCH 1-24

19..24

19..24

TCH 1-24

TC_PCM 4 TCH 1-24

TC_PCM 5 25..30 TCH 1-24

Figure 23.

80 (92)

Submultiplexing on Ater PCM in ANSI environment (16 kbit/s)

# Nokia Corporation

DN9812391 Issue 12-0 en


Ater PCM

Branch PCM

Main PCM LAPD

TC_PCM 3

1..6

1..12

LAPD

1..12

TCH 1-12

TC_PCM 1

TC_PCM 1

TCH 1-24

TCH 1-24

7..12

13..18

13..24

13..24

TC_PCM 2 TCH 1-24

TC_PCM 2 TCH 1-24

19..24

TC_PCM 3 25..30 TCH 1-12

Figure 24.


Branch PCM

Main PCM LAPD

TC_PCM 2

1..6

1..24 TC_PCM 1

Ater PCM LAPD

1..24 TC_PCM 1

TCH 1-6

TCH 1-24

TCH 1-24

7..12

13..18

19..24

TC_PCM 2 25..30 TCH 1-6

Figure 25.

DN9812391 Issue 12-0 en


# Nokia Corporation

81 (92)


Branch PCM

Main PCM LAPD

1..12

TC_PCM 1

1..6

TC_PCM 2 cont.

Ater PCM LAPD

1..12

TCH 13-18

TCH 1-24

TC_PCM 1 TCH 1-24

7..12

13..24

TC_PCM 2

13..18

13..30 TC_PCM 2

TCH 1-12

TCH 1-18

19..24

Figure 26.

11.2

Submultiplexing on Ater PCM in ANSI environment (mixed 32 and 64 kbit/s)

Compressed Abis time slot allocation Compressed time slot allocation is rarely used and limitations apply (not all BTS families support this feature). In traditional transmission solutions some capacity is left unused, especially in the case of BTSs with one TRX, because one radio interface time slot is always used for the BCCH. The compressed Abis time slot allocation makes it possible to use this capacity for TRX signalling. It is also possible to use another 16 kbit/s slot to carry the O & M signalling required for the site. This slot can 'steal' the TCH transmission slot thus leaving capacity for six full rate TCHs or twelve half rate TCHs for that TRX. In environments where it is not necessary to use the full traffic capacity of a TRX, compressed Abis time slot allocation offers an ideal solution for using the transmission medium more efficiently. With this configuration, it is possible to fit 15 TRXs to one 2 Mbit/s PCM. The following table illustrates this solution.

82 (92)

# Nokia Corporation

DN9812391 Issue 12-0 en


Table 8.

Compressed Abis time slot allocation

TRXSIG/OMUSIG

TCH, TSL1

TCH, TSL2

TCH, TSL3

TCH, TSL4

TCH, TSL5

TCH, TSL6

TCH, TSL7

The solution is particularly advisable in low traffic areas where it is essential to have coverage.

Note The time slot allocation of both BSC and BTS is of semipermanent type and cannot be dynamically altered. In a multi-TRX sector, radio network recovery may swap the positions of BCCH-TRXs and TCH-TRXs and so make it impossible to predict the branching requirements of the transmission. Another option for making the use of Abis interface more efficient is better suitable for multi-TRX BTSs. The following table illustrates the time slot allocation in this case.

Table 9.

Compressed Abis time slot allocation in the case of multi-TRX base stations

TRXSIG

TCH, TSL1

TCH, TSL2

TCH, TSL3

TCH, TSL4

TCH, TSL5

TCH, TSL6

TCH, TSL7

Here the first time slot of every TRX must be disabled at the BSC to leave space for the signalling. Possible reconfigurations may influence the time slot allocation. An additional 16 kbit/s subslot must be allocated for O & M signalling. By combining the above solutions it is possible to support five 3 x 1 TRX sites with a single 2 Mbit/s PCM link. The time slot allocation of one site in this case is illustrated in the following table.

Table 10.

Compressed Abis time slot allocation that supports five 3 x 1 TRX sites

OMU/TRXSIG_1

TCH, TSL1

TCH, TSL2

TCH, TSL3

TCH, TSL4

TCH, TSL5

TCH, TSL6

TCH, TSL7

TRXSIG_2

TCH, TSL1

TCH, TSL2

TCH, TSL3

DN9812391 Issue 12-0 en

# Nokia Corporation

83 (92)


Table 10.

Compressed Abis time slot allocation that supports five 3 x 1 TRX sites (cont.)

TCH, TSL4

TCH, TSL5

TCH, TSL6

TCH, TSL7

TRXSIG_3

TCH, TSL1

TCH, TSL2

TCH, TSL3

TCH, TSL4

TCH, TSL5

TCH, TSL6

TCH, TSL7

If the TRX signalling speed is 32 kbit/s, the following allocation is also possible.

Table 11.

Compressed Abis time slot allocation with the TRX signalling speed 32 kbit/s

TRXSIG/OMU TCH, TSL4

84 (92)

TCH, TSL5

# Nokia Corporation

TCH, TSL2

TCH, TSL3

TCH, TSL6

TCH, TSL7

DN9812391 Issue 12-0 en


TCH4/7-8 TCH8/15-16

TRX1

TCH6/11-12

TCH3/5-6 TCH7/13-14

TRXSIG2 TCH5/9-10 TRXSIG3 TCH5/9-10

OMUSIG2 TCH6/11-12 OMUSIG3 TCH6/11-12

TCH3/5-6 TCH7/13-14 TCH3/5-6 TCH7/13-14

TCH4/7-8 TCH8/15-16 TCH4/7-8 TCH8/15-16

TRX2

TRXSIG4 TCH5/9-10

OMUSIG4 TCH6/11-12

TCH3/5-6 TCH7/13-14

TCH4/7-8 TCH8/15-16

TRX4

OMUSIG5 TCH6/11-12 OMUSIG6

TCH3/5-6 TCH7/13-14 TCH3/5-6

TCH4/7-8 TCH8/15-16 TCH4/7-8

TRX5

11

TRXSIG5 TCH5/9-10 TRXSIG6

12

TCH5/9-10

TCH6/11-12

TCH7/13-14

TCH8/15-16

13

OMUSIG7 TCH6/11-12

TCH3/5-6 TCH7/13-14

TCH4/7-8 TCH8/15-16

TRX7

14

TRXSIG7 TCH5/9-10

15 16 17



TCH3/5-6 TCH7/13-14 TCH3/5-6

TCH4/7-8 TCH8/15-16 TCH4/7-8

TRX8

18 19

TCH5/9-10

TCH6/11-12

TCH7/13-14

TCH8/15-16



TCH3/5-6 TCH7/13-14

23

TCH5/9-10 TRXSIG12

TCH6/11-12 OMUSIG12

TCH3/5-6 TCH7/13-14 TCH3/5-6

TCH4/7-8 TCH8/15-16 TCH4/7-8

24

TCH5/9-10

TCH6/11-12

TCH7/13-14

TCH8/15-16

25 26 27



TCH3/5-6 TCH7/13-14 TCH3/5-6

TCH4/7-8 TCH8/15-16 TCH4/7-8

28 29 30

TCH5/9-10 TRXSIG15 TCH5/9-10

TCH6/11-12 OMUSIG15 TCH6/11-12

TCH7/13-14 TCH3/5-6 TCH7/13-14

TCH8/15-16 TCH4/7-8 TCH8/15-16

31

x/OMUSIG

x/OMUSIG

x/OMUSIG

x/OMUSIG

1

TRXSIG1

OMUSIG1

2

TCH5/9-10

3 4 5 6 7 8 9

10

20 21

22

Figure 27.

TCH8/15-16 TCH4/7-8

TRX3

TRX6

TRX9 TRX10 TRX11

TRX12 TRX13 TRX14 TRX15

Compressed allocation enabling up to 15 TRXs per 2 Mbit/s circuit

Note This is achieved at the cost of speech capacity.

DN9812391 Issue 12-0 en

# Nokia Corporation

85 (92)


As presented in Figure Compressed allocation enabling up to 15 TRXs per 2 Mbit/s circuit above, some speech capacity is lost for signalling. FR or HR speech can be used. HR can in this case be used with 16 kbit/s TRX signalling; 32 kbit/s is also possible but it may waste capacity. Further speech TCH capacity is gained by filling TSL31 with up to four OMUSIG channels.

1

2

3 4 5 6

TRXSIG1 TCH5/9-10 TRXSIG2 TCH5/9-10 TRXSIG3 TCH5/9-10

Figure 28.

11.3

OMUSIG1 TCH6/11-12 TCH2/3-4 TCH6/11-12 TCH2/3-4 TCH6/11-12

TCH3/5-6 TCH7/13-14 TCH3/5-6 TCH7/13-14 TCH3/5-6 TCH7/13-14

TCH4/7-8 TCH8/15-16 TCH4/7-8 TCH8/15-16 TCH4/7-8 TCH8/15-16

TRX1

TRX2 TRX3

Allocation example for a three-TRX BTS

Allocation of Abis time slots The allocation of time slots is based on the following principles: One 2 Mbit/s time slot 0 is reserved for ITU-T-type frame alignment and supervision of the link.

.

One 16 kbit/s (or 64 kbit/s) channel is required between the BTS and the BSC for BTS O & M (marked as OMUSIG).

.

Each TRX at the BTS processes up to 8 TCH/F traffic channels of 16 kbit/s or up to 16 TCH/H traffic channels, and a 16 kbit/s, 32 kbit/s (or 64 kbit/s) signalling link to the BSC (marked as TRXSIG). The FR and HR channels can be used at the same time call by call in the TRX.

.

The following tables present the different maximum numbers of TRXs per 2 Mbit/s PCM with 16 kbit/s and 64 kbit/s BCFSIG channel rates.

Table 12.

86 (92)

16 kbit/s signalling rate

Signalling rate

Point-to-point

Chain

Loop

16

13*

12

11

32

12

11

10

64

10

9

9

# Nokia Corporation

DN9812391 Issue 12-0 en


Table 12.

16 kbit/s signalling rate (cont.)

Compressed

15 *)

15

14

*) The maximum capacity is not possible because the number of TRXs that can be installed per BTS cabinet is 12.

Table 13.

64 kbit/s signalling rate

Signalling rate

Point-to-point

Chain

Loop

16

13 *)

9

9

32

12

8

8

64

10

7

7

*) The maximum capacity is not possible because the number of TRXs that can be installed per BTS cabinet is 12. The required time slot allocation is selected from the TRU menu from among certain time slot allocations. The TRU is able to drop and insert full time slots (for 64 kbit/s signalling) or parts of a time slot (for 16 kbit/s signalling) without restrictions. This means that the allocation on the 2 Mbit/s highway between the BSC and the BTS (or between the BTSn and BTSn + 1) can be freely selected.

11.4

TRU TSL allocation, FR, 16 kbit/s signalling The time slot allocation principle is the following: .

Eight 16 kbit/s TCH/Fs per each TRX

.

One 16 kbit/s TRXSIG (LAPD TRX - BSC) per each TRX

.

One 16 kbit/s OMUSIG (LAPD OMU - BSC) per each BTS

Space is allocated for these so that the 8 TCHs occupy two entire time slots. The TRXSIG uses one quarter of a time slot and the OMUSIG uses another quarter.

DN9812391 Issue 12-0 en

# Nokia Corporation

87 (92)


The TRU multidrop chain time slot allocation is presented in Figure 29 TRU chain allocation in the case of 16 kbit/s LAPD. This allocation can be used on the 2M highway. Note that the TRU drop/insert function must be used to build a correct internal D-bus allocation. This can be done by conforming to the rules given in the figure mentioned. It is possible to use any other allocation on the 2M highway. Along the BTS chain, time slots will be dropped or inserted and vacant time slots will be formed. These vacant time slots can be used for other purposes with suitable equipment. This allocation is flexible enough to cover typical applications where the number of TRXs per BTS is not greater than 12. Unused bits, marked with x, are set to one.

88 (92)

# Nokia Corporation

DN9812391 Issue 12-0 en


BIT TSL 0 1

TCH.1

2

TCH.5

3

TCH.1 TCH.5

4 5 6

TCH.1 TCH.5

7

TCH.1

8

TCH.5 TCH.1 TCH.5

9

10 11

12

TCH.1 TCH.5

13 14 15

TCH.1

16 17 18 19 20

TCH.5 TCH.1 TCH.5

21

22

TCH.1 TCH.5

23 24

TCH.1 TCH.5

25 26 27 28 29 30

TRXSIG1 TRXSIG3

31

TCH.5 TCH.1

TCH.1

TCH.5

TRXSIG5 TRXSIG7 TRXSIG9 TRXSIG11 X

Figure 29.

DN9812391 Issue 12-0 en

2

1

3

4

5

6

LINK MANAGEMENT TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TCH.2 TCH.3 TCH.6 TCH.7 TRXSIG2 OMUSIG1 TRXSIG4 OMUSIG3 OMUSIG5 TRXSIG6 OMUSIG7 TRXSIG8 OMUSIG9 TRXSIG10 TRXSIG12 OMUSIG11 X x

7

8

TCH.4 TCH.8 TCH.4 TCH.8 TCH.4 TCH.8

TRX1

TCH.4 TCH.8 TCH.4 TCH.8 TCH.4 TCH.8 TCH.4 TCH.8 TCH.4

TRX4

TCH.8 TCH.4 TCH.8 TCH.4 TCH.8 TCH.4 TCH.8 TCH.4 TCH.8 OMUSIG2 OMUSIG4 OMUSIG6 OMUSIG8 OMUSIG10 OMUSIG12 x

TRX2 TRX3

TRX5 TRX6 TRX7 TRX8 TRX9 TRX10 TRX11

TRX12

TRU chain allocation in the case of 16 kbit/s LAPD

# Nokia Corporation

89 (92)


Note The number of BTSs served may be anything up to 12, with the TRXs shared between them; TSL31 is unused or reserved for redundancy purposes, such as loop control bits.

11.5

TRU TSL allocation, FR/HR, 64 kbit/s signalling This allocation is not normally used because of its high requirement of capacity.

11.6

TRU TSL allocation, FR/HR, 32 kbit/s signalling The allocation principle is the following: .

Eight 16 kbit/s TCH/Fs or sixteen 8 kbit/s TCH/Hs

.

One 32 kbit/s TRXSIG (LAPD TRX - BSC) per TRX

.

One 16 kbit/s OMUSIG (LAPD OMU - BSC) per BTS

These are arranged so that one TRX TCH occupies two entire time slots. The TRXSIG uses half of one time slot and the OMUSIG uses one quarter of time slot 31. It is possible to use 16 kbit/s TRX signalling with HR, but for the best results, 32 kbit/s is recommended. During the network transition phase, 16 kbit/s may be advantageous. In the allocation example given in Figure An example of four-BTS TRU chain (highway) allocation when 32 kbit/s TRX signalling is used presented below, the number of BTSs served can be up to four with the 12 TRXs shared between them. The number of OMUSIGs can be increased by decreasing the number of TRXSIGs — a trade-off between the number of BTSs and the number of TRXs in the BTSs. In the following figure, for example T1/1-2 denotes either the first full rate channel TCH/F.1 or the first two half rate channels TCH/H.1 and TCH/H.2 of an Abis trunk. The BTS/TRX will dynamically support any combination of full rate and half rate channels call by call.

90 (92)

# Nokia Corporation

DN9812391 Issue 12-0 en


BIT TSL 0 1

2 3 4 5 6 7 8 9

10 11

12

13 14 15 16 17 18 19 20 21

22

23 24 25 26 27 28 29 30 31

1

3

4

5

6

7

8

LINK MANAGEMENT T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T7/13-14 T8/15-16 T611-12 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T2/3-4 T3/5-6 T4/7-8 T1/1-2 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T7/13-14 T8/15-16 T611-12 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 T1/1-2 T2/3-4 T3/5-6 T4/7-8 T5/9-10 T611-12 T7/13-14 T8/15-16 TRXSIG2 TRXSIG1 TRXSIG3 TRXSIG4 TRXSIG6 TRXSIG5 TRXSIG8 TRXSIG7 TRXSIG9 TRXSIG10 TRXSIG12 TRXSIG11 OMUSIG3 OMUSIG4 OMUSIG2 OMUSIG1

Figure 30.

DN9812391 Issue 12-0 en

2

TRX1

TRX2 TRX3 TRX4 TRX5 TRX6 TRX7 TRX8 TRX9 TRX10 TRX11

TRX12

An example of four-BTS TRU chain (highway) allocation when 32 kbit/s TRX signalling is used

# Nokia Corporation

91 (92)

Nokia Bss Transmission

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