BSC3153 Nokia GSM/EDGE BSS, Rel. BSS13, BSC and TCSM, Rel. S13, Product Documentation, v.1
GSM-WCDMA Interworking
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GSM-WCDMA Interworking
The information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This documentation is intended for the use of Nokia Siemens Networks customers only for the purposes of the agreement under which the document is submitted, and no part of it may be used, reproduced, modified or transmitted in any form or means without the prior written permission of Nokia Siemens Networks. The documentation has been prepared to be used by professional and properly trained personnel, and the customer assumes full responsibility when using it. Nokia Siemens Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation. The information or statements given in this documentation concerning the suitability, capacity, or performance of the mentioned hardware or software products are given “as is” and all liability arising in connection with such hardware or software products shall be defined conclusively and finally in a separate agreement between Nokia Siemens Networks and the customer. However, Nokia Siemens Networks has made all reasonable efforts to ensure that the instructions contained in the document are adequate and free of material errors and omissions. Nokia Siemens Networks will, if deemed necessary by Nokia Siemens Networks, explain issues which may not be covered by the document. Nokia Siemens Networks will correct errors in this documentation as soon as possible. IN NO EVENT WILL NOKIA SIEMENS NETWORKS BE LIABLE FOR ERRORS IN THIS DOCUMENTATION OR FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO SPECIAL, DIRECT, INDIRECT, INCIDENTAL OR CONSEQUENTIAL OR ANY LOSSES, SUCH AS BUT NOT LIMITED TO LOSS OF PROFIT, REVENUE, BUSINESS INTERRUPTION, BUSINESS OPPORTUNITY OR DATA, THAT MAY ARISE FROM THE USE OF THIS DOCUMENT OR THE INFORMATION IN IT. This documentation and the product it describes are considered protected by copyrights and other intellectual property rights according to the applicable laws. The wave logo is a trademark of Nokia Siemens Networks Oy. Nokia is a registered trademark of Nokia Corporation. Siemens is a registered trademark of Siemens AG. Other product names mentioned in this document may be trademarks of their respective owners, and they are mentioned for identification purposes only. Copyright © Nokia Siemens Networks 2008. All rights reserved.
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Contents
Contents Contents 3 List of tables 4 List of figures 5 Summary of changes 7 1 1.1 1.2 1.3
Overview of GSM-WCDMA Interworking 11 GSM-WCDMA cell re-selection and inter-system handover WCDMA-GSM cell re-selection and inter-system handover Benefits of GSM-WCDMA interworking 16
2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11
System impact of GSM-WCDMA Interworking 19 Requirements 20 Restrictions 21 Impact on transmission 22 Impact on BSS performance 22 User interface 23 Impact on Network Switching Subsystem (NSS) 29 Impact on NetAct products 31 Impact on mobile stations 31 Impact on interfaces 32 Impact on capacity 33 Interworking with other features 33
3 3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.3
Planning GSM-WCDMA Interworking 35 GSM-WCDMA cell re-selection in idle state 35 GSM-WCDMA handover process 40 Inter-System Direct Access 43 Inter-System handover penalties and timers 44 Support of service priorities in A-interface 46 WCDMA RAN cell measurements for GSM-WCDMA inter-system handover 47 UE camping on a 3G cell after a call release 52
4
Implementing GSM-WCDMA Interworking overview 55
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List of tables
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Table 1.
Required additional or alternative hardware or firmware
20
Table 2.
Required software
Table 3.
Impact of GSM-WCDMA Interworking on BSC units
Table 4.
Counters of Handover Measurement related to GSM-WCDMA Interworking 26
Table 5.
Counters of BSC Level Clear Code (PM) Measurement related to GSMWCDMA Interworking 27
Table 6.
Counters of BSC Level Clear Code (SERLEV) Measurement related to GSM-WCDMA Interworking 27
Table 7.
Counters of UTRAN Handover Adjacent Cell Measurement related to GSM-WCDMA Interworking 28
Table 8.
Counters of UTRAN Neighbouring Cell Signal Level Measurement related to GSM-WCDMA Interworking 29
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List of figures
List of figures Figure 1.
GSM-WCDMA RAN network architecture
Figure 2.
Load and coverage based handovers
Figure 3.
Example of UE idle mode camping in UTRAN
Figure 4.
Cell re-selection process (Non-GPRS/EDGE capable phone)
Figure 5.
GSM-WCDMA inter-system handover process
Figure 6.
Measurement quantity is EC/lo (reported as Ec/No classification value) 49
Figure 7.
Cell selection in idle mode camping
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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 7 and 6 References to PCCCH/PBCCH have been removed. Chapter Overview of GSM-WCDMA Interworking has been reorganised. Figure Load and coverage based handovers has been added and updated to include Coverage Based ISHO in Dedicated Mode application software. In Benefits of GSM-WCDMA interworking, information on the coverage based handover from GSM BSS to WCDMA RAN has been added. Chapter System impact of GSM-WCDMA Interworking has been added. The required software table has been updated. Information on Nokia PrimeSite BTS and Nokia 2nd generation BTS has been removed. Parameters GPRS fdd cell reselect offset and GPRS minimum fdd threshold have been removed. Parameters minimum fdd threshold offset, minimum RSCP threshold, and fdd reporting threshold 2 have been added. FIFILE parameter ISHO_SUPPORT_IN_BSC and GPRS license control have been added. Subchapters Impact on Network Switching Subsystem (NSS), Impact on mobile stations, and Impact on interfaces have been updated. In Restrictions and Interworking with other features, information on GSM - TD-SCDMA Interworking has been added.
Functionality of GSM-WCDMA Interworking has been reorganised and renamed as Planning GSM-WCDMA Interworking:
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.
Title of subchapter Inter-system handover from GSM to WCDMA has been changed to GSM-WCDMA cell re-selection in idle state.
.
Subchapters Cell re-selection with non-GPRS/EDGE capable UEs and Cell re-selection with GPRS/EDGE capable UEs have been removed and their contents updated and incorporated into this section.
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.
Information on new parameters related to the CPICH RSCP Based Criterion for 2G and 3G Cell Re-selection application software product has been added. Figures have been updated accordingly.
.
In subchapter GSM-WCDMA handover process, a parameter number of measured FDD cells (FDMR) has been added to replace threshold for multi-RAT MS, service priority, and min traffic load for speech call parameters to prevent the neighbour WCDMA RAN cell measurements, and inter-system handovers from a GSM cell to WCDMA RAN.
.
Subchapter IMSI-based GSM-WCDMA Handover has been removed.
.
Subchapter Support of service priorities in A-interface has been updated.
.
In subchapter WCDMA RAN cell measurements for GSM-WCDMA inter-system handover, topic 'WCDMA RAN neighbour cell reporting enhancement' has been added.
.
Subchapter UE camping on a 3G cell after a call release has been added.
Subchapter Inter-system handover from WCDMA to GSM has been removed. Chapter Implementing GSM-WCDMA Interworking overview has been added. Chapters Requirements for GSM-WCDMA Interworking, Technical description of GSM-WCDMA Interworking, Effect of GSM-WCDMA Interworking on interfaces, and User interface of GSM-WCDMA Interworking have been removed.
Changes made between issues 6 and 5 In Overview of GSM-WCDMA Interworking, a list of related topics has been added. In Functionality of GSM-WCDMA Interworking, the information that the UE's measured RCSP value is used as a criteria for cell re-selection has been added. Information on Dual Transfer Mode interworking has been added. The terms mobile and mobile station have been replaced with the term user equipment (UE).
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Summary of changes
Changes made between issues 5 and 4 Name of the document has been changed from GSM-WCDMA InterSystem Handover to GSM-WCDMA Interworking. Overview of GSM-WCDMA Interworking Title of this chapter has been changed. Requirements for GSM-WCDMA Interworking Information in this new chapter is based on chapter Planning BSS10101: GSM-WCDMA Inter-System Handover and BSS11107: GSM-WCDMA Inter-System Direct Access in the previous issue of this document. Technical description of GSM-WCDMA Interworking Information on counters and measurements and parameters moved from this chapter to chapter User Interface of GSM-WCDMA Inter-System Handover. Subchapter Interworking with other application software: Information on ISNCCR and IBHO added. Functionality of GSM-WCDMA Interworking Information in this new chapter is based on chapters: WCDMA RAN cell measurements in GSM-WCDMA Inter-System Handover, Cell reselection from GSM/GPRS to WCDMA RAN, and Handover from GSM to WCDMA RAN in dedicated state in the previous issue of this document. Effect of GSM-WCDMA Interworking on interfaces Information in this new chapter is based on chapter Support of service priorities in A-interface in the previous issue of this document. Information on Gb interface added. User interface of GSM-WCDMA Interworking Information in this new chapter is moved from chapter Technical description of GSM-WCDMA Interworking. Subchapter MML commands: Base Station Controller Handling (command group EE) added. The document has been revised throughout to comply with the latest documentation standards.
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Overview of GSM-WCDMA Interworking
1
Overview of GSM-WCDMA Interworking Universal Mobile Telecommunications System (UMTS) is a European 3rd generation mobile system based on wideband code division multiple access (WCDMA). In the 3GPP standard specifications, the UMTS terrestrial radio access network (UTRAN) is a radio access network which consists of radio network controllers (RNC) and WCDMA base transceiver stations (WBTS) and which is located between the Iu interface and the WCDMA radio interface. The UMTS network consists of the UTRAN and the core network.
Network Architecture BTS
Abis
A BSC
BTS
MSC/VLR
GMSC
HLR
SCP
PSTN/ ISDN
GSM BSS Gb
Dual mode UE
lub WBTS SGSN
RNC WBTS lur WBTS
3G-SGSN
RNC WBTS
GGSN
lu
IP NETWORKS
WCDMA RAN
Figure 1.
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GSM-WCDMA RAN network architecture
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GSM-WCDMA Interworking
In the Nokia solution, the UMTS network is called '3G' and its UTRAN is called 'WCDMA RAN' according to the used radio interface technique. In this description, the EDGE functionality is covered as part of GSM and GPRS, when necessary. EDGE itself does not affect the inter-system handover algorithms or inter-system user-defined parameters in the BSC. An inter-system handover (ISHO) is a handover between the GSM and WCDMA networks. The change from GSM to WCDMA network or vice versa can also take place in idle mode when there is cell re-selection. For packet data, the cell re-selection is done even if the user equipment (UE) is not in idle mode. GSM-WCDMA Interworking consists of the following application software products: .
BSS10101: GSM-WCDMA Inter-System Handover
.
BSS11107: GSM-WCDMA Inter-System Direct Access
.
BSS20477: CPICH RSCP Based Criterion for 2G to 3G Cell Reselection
.
BSS20858: WCDMA Neighbour Cell Reporting Enhancement
.
BSS20132: Mobile Specific Channel Release Message
.
BSS20967: Coverage Based ISHO in Dedicated Mode
All of these software products are licence-based except for GSM-WCDMA Inter-System Handover. Using GSM-WCDMA Inter-System Handover requires that you activate the FIFILE parameter options. The dual mode GSM/WCDMA UEs are divided into two categories: GPRS/ EDGE and non-GPRS/EDGE capable UEs. There are both common and category-specific operator parameters for the adjustment of user equipment (UE) functionality in the idle state, packet idle mode, dedicated state, and packet transfer mode. For the BSC radio network parameter handling, this means that most of the WCDMA related idle state parameters are applicable for all UE. However, the operator is also able to define the neighbour-WCDMA cell measuring and re-selection threshold values specific for the GPRScapable WCDMA UE. The inter-system handover from GSM to WCDMA is initiated by the GSM radio network, and the inter-system handover from WCDMA to GSM is initiated by the WCDMA radio network (UTRAN).
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Overview of GSM-WCDMA Interworking
For the operator to be able to provide seamless coverage in areas where WCDMA or GSM is not available, for example in rural areas, inter-system handovers provide a method of extending the radio network coverage area by making a handover between the WCDMA network and GSM network. In addition, in situations where the WCDMA network and GSM network overlap, an inter-system handover can be made to balance or control the traffic load between the systems. An example of this is where the speech connection is handed over to the GSM network to allow data connections to be handled by the WCDMA network. Inter-system handovers are hard handovers, which means that an intersystem handover causes a temporary disconnection of the real time (RT) radio access bearer. Inter-system handovers are also network-evaluated handovers (NEHO). However, the user equipment must be capable of supporting inter-system handovers completely before GSM-WCDMA Inter-System Handover can be used.
1.1
GSM-WCDMA cell re-selection and inter-system handover GSM-WCDMA Inter-System Handover application software enables UEcontrolled inter-system cell re-selections for the WCDMA-capable dual mode GSM/WCDMA UE from: .
GSM to WCDMA RAN in idle state
.
GPRS to WCDMA RAN in packet idle mode
.
GPRS to WCDMA RAN in packet transfer mode for PS connections
For a dual mode GSM/WCDMA UE, GSM-WCDMA Inter-System Handover application software enables the measurements and cell reselection of neighbour WCDMA RAN cells while the UE has been camped on a GSM cell in the idle state. UE-controlled inter-system cell re-selections towards WCDMA RAN are always initiated because of downlink signal quality reasons. The dual mode user equipment make inter-system cell re-selection attempt decisions according to the WCDMA-related idle state parameters, neighbour cell measurements, and inter-system cell re-selection algorithms.
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GSM-WCDMA Inter-System Handover deals with the BSC-controlled handovers that occur between the GSM and the WCDMA RAN for circuit switched (CS) connections. The handovers can take place from the GSM BSS to WCDMA RAN, and vice versa, when the dual mode GSM/WCDMA UE is in the dedicated state. GSM-WCDMA Inter-System Handover application software enables the BSC to receive all incoming inter-system handovers (that is, from the WCDMA RAN) and inter-system cell re-selections. GSM-WCDMA Inter-System Handover application software supports both CS and PS modes. Information that the dual mode GSM/WCDMA UE can perform cell reselections and handovers to WCDMA RAN is included in the SYSTEM INFORMATION and MEASUREMENT INFORMATION messages. Information on WCDMA RAN cells is included and broadcast in these messages only if you have defined the cells as neighbour WCDMA RAN cells for the serving GSM cell. The figure Load and coverage based handovers illustrates handovers that are based on the load and coverage situation in the serving cell. There are also handovers that are based on traffic and services.
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Overview of GSM-WCDMA Interworking
Usually an inter-system handover is triggered if the load of the GSM cell exceeds the load threshold. When higher priority intra GERAN handover criteria is met but no target GSM cell can be found, the BSC can trigger inter-system handover even if the load of the source cell is below the load threshold.
Load threshold
GSM
GSM
3G
Dual mode mobile
GSM Load reason handover from GSM to 3G
Figure 2.
1.2
GSM
GSM
3G
3G
3G
GSM Coverage reason handover from 3G to GSM
3G
3G Coverage reason handover from GSM to 3G
Load and coverage based handovers
WCDMA-GSM cell re-selection and inter-system handover The handover control of the RAN supports inter-system handovers, both from WCDMA to GSM and from GSM to WCDMA. Inter-system handover is required so that the coverage areas of GSM and WCDMA can complement each other. When the coverage areas of WCDMA and GSM are overlapping each other, an inter-system handover can be used to control the load and/or services between the systems. Both circuitswitched (CS) and packet-switched (PS) services can be maintained between GSM and WCDMA networks. The network-initiated cell re-selection (for packet data) from WCDMA to GPRS/EDGE and inter-system handover (for circuit-switched data) from WCDMA to GSM are network-evaluated handovers. The decision algorithm of the inter-system handover and network-initiated cell reselection is located in the Radio Network Controller (RNC). The RNC
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makes the decision based on the periodical inter-system measurement reports received from the UE and relevant control parameters. The RNC orders the UE to start the periodical reporting of inter-system measurement results only when an inter-system handover or cell reselection is needed. The measurement object information (cells and frequencies) for the inter-system measurement is determined by the RNC. Unless the UE is equipped with dual receivers it can only be tuned to one frequency at a time. Therefore, compressed mode must be used at the physical layer of the radio interface to allow the UE to make the required inter-system (GSM) measurements while maintaining its existing connection. For more information, see Handover Control in Nokia WCDMA RAN, System Library.
1.3
Benefits of GSM-WCDMA interworking .
When the networks overlap, handovers from GSM BSS to WCDMA RAN can be made in order to reduce traffic load in the GSM network.
.
Handovers from WCDMA RAN to GSM BSS can be made to enable the operator to provide a seamless coverage in areas where WCDMA RAN is not available. The handover extends the radio network coverage.
.
Due to the inter-system handover, seamless continuity of speech connections and certain data services between WCDMA RAN and GSM networks are available for all dual mode subscribers. Dual mode UEs support both GSM and WCDMA RAN. In addition to this, dual mode UEs may also support GPRS/EDGE.
.
Handovers from GSM BSS to WCDMA RAN can be made to enable the operator to provide a seamless coverage in areas where GSM is not available. The handover extends the radio network coverage.
Other related topics .
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Test and activate . Radio network performance . BSS10101, BSS11107, BSS20477, BSS20858 and BSS20132: GSM-WCDMA Interworking . Activating and Testing BSS10101, BSS11107, BSS20477, BSS20858 and BSS20132: GSMWCDMA Interworking
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Overview of GSM-WCDMA Interworking
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.
Reference . Commands . MML commands . EA – Adjacent Cell Handling . EE – Base Station Controller Parameter Handling in BSC . EG – GSM Timer and BSC Parameter Handling . EH – Handover Control Parameter Handling . EQ – Base Transceiver Station Handling in BSC . Counters/Performance indicators . Call control measurements (CS) . 4 Handover Measurement . 51 BSC Level Clear Code (PM) Measurement . 57 BSC Level Clear Code (SERLEV) Measurement . 93 UTRAN Handover Adjacent Cell Measurement . 94 UTRAN Neighbouring Cell Signal Level Measurement . Parameters . BSS Radio Network Parameter Dictionary . PAFILE Timer and Parameter List
.
Descriptions . Functional descriptions . Radio network performance . RF Power Control and Handover Algorithm . GSM - TD-SCDMA Interworking . Feature descriptions . Radio network performance . Common BCCH Control in BSC . IMSI-based Handover . Data . Dual Transfer Mode . GPRS/EDGE System Feature Description . Inter-System Network-Controlled Cell Re-selection
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System impact of GSM-WCDMA Interworking
2
System impact of GSM-WCDMA Interworking The system impact of GSM-WCDMA Interworking including the following features is specified in the sections below: .
BSS10101: GSM-WCDMA Inter-System Handover
.
BSS11107: GSM-WCDMA Inter-System Direct Access
.
BSS20477: CPICH RSCP Based Criterion for 2G and 3G Cell Reselection
.
BSS20858: WCDMA Neighbour Cell Reporting Enhancement
.
BSS20132: Mobile Specific Channel Release Message
.
BSS20967: Coverage Based ISHO in Dedicated Mode
For planning information, see GSM-WCDMA cell re-selection in idle state. For implementation instructions, see Implementing GSM-WCDMA Interworking. GSM-WCDMA Interworking is an application software product.
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2.1
Requirements Hardware requirements
Table 1.
Required additional or alternative hardware or firmware
Network element HW/FW required BSC
No requirements
BTS
No requirements
TCSM
No requirements
SGSN
No requirements
MSC
No requirements
Software requirements
Table 2.
Required software
Network element Software release required
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BSC
S13
Nokia Flexi EDGE BTSs
EP2.0
Nokia UltraSite EDGE BTSs
CX6.0
Nokia MetroSite EDGE BTSs
CXM6.0
Nokia Talk-family BTSs
DF7.0
Nokia InSite BTSs
I3.0
MSC/HLR
M14
SGSN
SG7.0
Nokia NetAct
OSS4.2
RNC
RN3
WBTS
WN1.3-3
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System impact of GSM-WCDMA Interworking
Frequency band support for GSM-WCDMA Interworking The BSC supports GSM-WCDMA Interworking on the following frequency bands:
2.2
.
GSM 800
.
GSM 900
.
GSM 1800
.
GSM 1900
Restrictions The following restrictions apply to GSM-WCDMA Interworking: The maximum number of neighbour WCDMA RAN cells per a serving cell is limited to 32. If GSM-WCDMA Inter-System Handover application software is in use, the maximum number of neighbour GSM cells (ADJC) per a serving cell (or segment) is: .
31 without Common BCCH Control
.
30 if Common BCCH Control is activated
If the GSM-WCDMA Inter-System Handover application software is in use, the maximum number of frequencies in a BCCH Allocation (BA) list is: .
31 without Common BCCH Control
.
30 if Common BCCH Control is activated
The UTRAN absolute radio frequency channel number (UARFCN) and the scrambling code combinations of neighbour WCDMA RAN cells, which are defined for the same segment, must be unambiguous. In other words, a segment cannot have two or more neighbour WCDMA RAN cells with the same UARFCN and scrambling code. The identifications of the neighbour WCDMA RAN cells, which are defined for the same serving GSM cell, must be unambiguous. In other words, a serving GSM cell cannot have two or more neighbour WCDMA RAN cells which use the same MCC+ MNC+ RNC ID + CI combination and/or WCDMA RAN cell index value.
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A BTS/SEG can have either adjacent WCDMA RAN cells or adjacent TDSCDMA RAN cells regardless of the fact that both GSM-WCDMA InterSystem Handover application software and TD-SCDMA idle mode support application software are active in the BSC. It is not recommended to use GSM-WCDMA Inter-System Handover application software and GSM TD-SCDMA Interworking application software at the same time in the same BSC. For more information, see GSM - TD-SCDMA Interworking under Feature descriptions/Radio network performance in the PDF view.
2.3
Impact on transmission No impact.
2.4
Impact on BSS performance OMU signalling No impact. TRX signalling No impact. Impact on BSC units
Table 3.
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Impact of GSM-WCDMA Interworking on BSC units
BSC unit
Impact
OMU
No impact
MCMU
No impact
BCSU
No impact
PCU
No impact
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System impact of GSM-WCDMA Interworking
2.5
User interface BSC MMI The following command groups are used for handling GSM-WCDMA Interworking: .
Adjacent Cell Handling: EA
.
Base Station Controller Parameter Handling in BSC: EE
.
GSM Timer and BSC Parameter Handling: EG
.
Handover Control Parameter Handling: EH
.
Base Transceiver Station Handling in BSC: EQ
For more information on the command groups and MML commands, see MML commands under Reference/Commands in the PDF view. BSC parameters
Base Station Controller (BSC) Parameters .
penalty trigger measurement period
.
triggering threshold for service area penalty
.
service area penalty time
Handover Control (HOC) Parameters
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.
threshold for multi-RAT MS
.
min traffic load for speech call
.
number of measured fdd cells
.
min interval between unsucc ISHO attempt
.
triggering ratio for WCDMA RAN cell penalty
.
WCDMA RAN cell penalty time
.
all adjacent WCDMA RAN cells averaged
.
adjacent WCDMA RAN cell averaging window size
.
number of WCDMA RAN zero results
.
inter-system direct access enabled
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.
fdd reporting threshold
.
fdd reporting threshold 2
SEG-specific Base Transceiver Station (SEG-BTS) Parameters .
GPRS threshold to search WCDMA RAN cells
.
threshold to search WCDMA RAN cells
.
fdd and tdd cell reselect offset
.
minimum fdd threshold
.
minimum fdd threshold offset
.
minimum RSCP threshold
Adjacent WCDMA RAN Cell (UADJC/ADJW) Parameters .
mobile country code
.
mobile network code
.
radio network controller identifier
.
cell identification
.
location area code
.
scrambling code
.
WCDMA downlink carrier frequency
.
downlink transmission diversity
.
minimum CPICH Ec/Io level
.
direct access Ec/Io threshold
.
service area code
.
adjacent cell index
For more information on radio network parameters, see BSS Radio Network Parameter Dictionary under Reference/Parameters in the PDF view.
PAFILE Timer parameters .
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GSM to WCDMA RAN handover procedure supervision in the source BSC (T3121)
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System impact of GSM-WCDMA Interworking
For more information, see GSM Timer and BSC parameter handling under Reference/Commands/MML commands in the PDF view and the parameter description in PAFILE Timer and Parameter List under Reference/Parameters in the PDF view.
FIFILE parameters .
ISHO_SUPPORT_IN_BSC
For more information, see PRFILE Timer and Parameter List under Reference/Parameters in the PDF view.
Licenses .
GPRS licence control
For more information, see Licensing in BSC under Install and upgrade/ Software in the PDF view. Alarms No impact. Measurements and counters The following measurements and counters are related to GSM-WCDMA Interworking.
4 Handover Measurement The Handover Measurement provides counters for incoming inter-system handovers from WCDMA RAN to GSM. The number of successful intersystem handovers and failed inter-system handover attempts by different failure causes on cell level are collected into the counters. The Handover Measurement also provides counters for outgoing intersystem handovers from GSM to WCDMA RAN. The number of handover commands, attempts, successes, and failures are collected into the counters. For more information, see 4 Handover Measurement under Reference/ Counters/Performance indicators/Call control measurements (CS) in the PDF view.
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Table 4.
Counters of Handover Measurement related to GSM-WCDMA Interworking
Name
Number
MSC I TCH HO FROM WCDMA RAN ATTEMPT
004144
MSC I WCDMA RAN HO ATTEMPT UNSUCC DUE LACK
004145
MSC I WCDMA RAN HO ATTEMPT UNSUCC DUE BSS PROBLEM
004146
MSC I WCDMA RAN END OF HO
004147
MSC I UNSUCCESS HO WCDMA RAN DUE CONN
004148
MSC I HO WCDMA RAN TCH SUCCESS
004149
MSC O TCH HO TO WCDMA RAN ATTEMPT
004150
MSC O HO TO WCDMA RAN NOT ALLOWED
004151
MSC O END OF HO TO WCDMA RAN DUE BSS
004152
MSC O GEN INTER SYSTEM TO WCDMA RAN HANDOVER REQ MESSAGES
004153
MSC O GEN INTER SYSTEM TO WCDMA RAN HANDOVER COM MESSAGES
004154
MSC O TO WCDMA RAN FAIL LACK
004155
MSC O END OF HO TO WCDMA RAN
004156
MSC O CALL DROP DURING HO TO WCDMA RAN
004157
MSC O TO WCDMA RAN SUCCESS TCH HO
004158
HO ATTEMPT DUE TO ISHO
004180
HO ATTEMPT DUE TO INTER SYSTEM DIRECT ACCESS
004181
MSC O SDCCH TCH HO TO WCDMA RAN ATTEMPT
004182
MSC O SDCCH TCH TO WCDMA RAN SUCCESS HO
004183
51 BSC Level Clear Code (PM) Measurement The BSC Level Clear Code (PM) Measurement provides counters for the successful incoming and outgoing inter-system handovers on the BSC level. For more information, see 51 BSC Level Clear Code (PM) Measurement under Reference/Counters/Performance indicators/Call control measurements (CS) in the PDF view.
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Table 5.
Counters of BSC Level Clear Code (PM) Measurement related to GSM-WCDMA Interworking
Name
Number
EXT IN ISHO
051151
EXT OUT ISHO
051152
EXT OUT INTER SYSTEM DIRECT ACCESS
051154
57 BSC Level Clear Code (SERLEV) Measurement The BSC Level Clear Code (SERLEV) Measurement provides counters for failures and successes of the inter-system handovers on cell level, based on the respective clear codes. For more information, see 57 BSC Level Clear Code (SERLEV) Measurement under Reference/Counters/Performance indicators/Call control measurements (CS) in the PDF view.
Table 6.
Counters of BSC Level Clear Code (SERLEV) Measurement related to GSM-WCDMA Interworking
Name
Number
WCDMA RAN TO GSM HO FAILURE TARGET
057039
WCDMA RAN TO GSM HO SUCCESS
057040
GSM TO WCDMA RAN HO FAILURE SOURCE
057041
GSM TO WCDMA RAN HO SUCCESS
057042
93 UTRAN Handover Adjacent Cell Measurement The UTRAN Handover Adjacent Cell Measurement collects statistics for the distribution of inter-system handovers between different cells. It contains counters for handover attempts and successful handovers in both directions, from GSM to WCDMA RAN and vice versa. The measurement also has separate counters for handover failures because of lack of resources. The counters are collected separately for each serving cell on the GSM side, and for each serving cell there are counters for their 32 defined WCDMA RAN neighbours, plus one counter collecting the possible handovers from the undefined WCDMA RAN cells. For more information, see 93 UTRAN Handover Adjacent Cell Measurement under Reference/Counters/Performance indicators/Call control measurements (CS) in the PDF view.
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Table 7.
Counters of UTRAN Handover Adjacent Cell Measurement related to GSM-WCDMA Interworking
Name
Number
LAC SAC 1
093000
PLMN ID 1
093001
HO ATT TO WCDMA RAN CELL 1
093002
HO SUCC TO WCDMA RAN CELL 1
093003
HO FAIL DUE RES TO WCDMA RAN CELL 1
093004
HO ATT FROM WCDMA RAN LAC SAC 1
093005
HO SUCC FROM WCDMA RAN LAC SAC 1
093006
HO FAIL DUE RES FROM WCDMA RAN LAC SAC 1
093007
... LAC SAC 32
093248
PLMN ID 32
093249
HO ATT TO WCDMA RAN CELL 32
093250
HO SUCC TO WCDMA RAN CELL 32
093251
HO FAIL DUE RES TO WCDMA RAN CELL 32
093252
HO ATT FROM WCDMA RAN LAC SAC 32
093253
HO SUCC FROM WCDMA RAN LAC SAC 32
093254
HO FAIL DUE RES FROM WCDMA RAN LAC SAC 32
093255
HO ATT FROM UNDEFINED WCDMA RAN CELLS
093256
HO SUCC FROM UNDEFINED WCDMA RAN CELLS
093257
HO FAIL DUE RES FROM UNDEFINED WCDMA RAN CELLS 093258 RNC ID CI 1
093259
... RNC ID CI 32
093290
94 UTRAN Neighbouring Cell Signal Level Measurement The UTRAN Neighbouring Cell Signal Level Measurement provides information on the signal levels of the WCDMA RAN cell in the neighbourhood of GSM serving cells. The measurements are performed by the dual mode (WCDMA/GSM) UE that are attached on a GSM cell. The measurement divides the signal level values in three classes according to the two user-defined class boundaries.
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For more information, see 94 UTRAN Neighbouring Cell Signal Level Measurement under Reference/Counters/Performance indicators/Call control measurements (CS) in the PDF view.
Table 8.
Counters of UTRAN Neighbouring Cell Signal Level Measurement related to GSM-WCDMA Interworking
Name
Number
LOWER EC/NO LIMIT
094000
UPPER EC/NO LIMIT
094001
LAC/RNC ID 1
094002
PLMN ID 1
094003
CELL ID 1
094004
ECNO REPORTS BELOW LOWER LIMIT 1
094005
ECNO REPORTS BETWEEN LIMITS 1
094006
EC/NO REPORTS ABOVE UPPER LIMIT 1
094007
... LAC / RNC ID 32
094188
PLMN ID 32
094189
CELL ID 32
094190
EC/NO REPORTS BELOW LOWER LIMIT 32
094191
EC/NO REPORTS BETWEEN LIMITS 32
094192
EC/NO REPORTS ABOVE UPPER LIMIT 32
094193
For more information, see Call Control Measurements (CS) under Reference/Counters/Performance indicators in the PDF view.
2.6
Impact on Network Switching Subsystem (NSS) Inter-system handover is a basic requirement for the operators who want to ensure a successful migration to 3G and want to be able to offer a wide range of high quality services for 2G and/or 3G subscribers. It enables a variety of business strategies for all types of operators, because roaming agreements are possible between GSM and UMTS operators and the operators can also support both GSM and UMTS in their own networks.
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When Inter-system handover and UMTS changes in MSC is activated, the inter-system handover (RNC <--> BSC) is supported in the MSC/MSC Server. This handover is possible in Inter MSC (Inter PLMN and Intra PLMN) and Intra MSC (Inter PLMN and Intra PLMN). Inter-system handover and UMTS requirements for the MSC/MSC Server To connect the UTRAN radio network to the MSC and to make intersystem handovers, the following functionality requirements for the MSC/ MSC Server must be fulfilled: .
Security Requirements due to Inter-system handover
.
Key handling in basic and subsequent Inter-MSC handovers
.
BSSMAP (3GPP Rel. 99) implementation in A interface
.
RANAP implementation in MAP E interface
.
MAP phase 3 implementation in E interface
.
Requirements coming from the support for Multiple RNCs per Multimedia gateway
.
Signalling requirements for Gs interface
.
Charging and Statistics support
.
Access and handover control
For detailed descriptions of the above mentioned requirements, see Feature 1260: Inter-system handover and UMTS changes in MSC in Nokia MSC/HLR Feature Activation Manuals. Handovers in the MSC Server System The MSC Server (MSS) System supports all standardised relocation and inter-system handover scenarios. From a control plane point of view, the handover signalling in Iu, A, and E-interfaces is similar to MSC architecture. The main difference is related to moving user plane connections from one MGW to another when necessary. For further information about handovers in CS Core Network, see Roaming and Handovers in CS Core Network in CS Core System Documentation.
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2.7
Impact on NetAct products NetAct Administrator No impact. NetAct Monitor No impact. NetAct Radio Access Configurator (RAC) With NetAct Radio Access Configurator tools it is possible to manage intersystem adjacencies and the related parameters. For more information, see Managing Adjacencies in Nokia NetAct Product Documentation. NetAct Reporter No impact. NetAct Tracing No impact.
2.8
Impact on mobile stations GSM-WCDMA Interworking requires a dual mode (GSM-WCDMA or GSM-GPRS-WCDMA) mobile station. The CPICH RSCP Based Criterion for 2G and 3G Cell Re-selection and WCDMA Neighbour Cell Reporting Enhancement application software products require a 3GPP Rel. 5 or newer dual mode MS. The Mobile Specific Channel Release Message software requires a 3GPP Rel. 6 dual mode MS. According to the 3GPP standard, a dual mode GSM/WCDMA UE is able to monitor a maximum of 32 FDD type WCDMA RAN cells on up to three frequencies. Note that the dual mode GSM/WCDMA UE's behaviour is not specified if the number of the 3G frequencies or other cell information elements sent exceeds the UE's monitoring capabilities as defined by the 3GPP standards.
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2.9
Impact on interfaces Impact on A interface GSM-WCDMA Interworking has an impact on the following messages: .
HANDOVER REQUEST (MSC -> BSS)
.
HANDOVER REQUIRED (BSS -> MSC)
.
HANDOVER COMMAND (MSC -> BSS)
Support of service priorities The BSC handles service priority indication in the ASSIGNMENT REQUEST and HANDOVER REQUEST messages. For more information, see Support of service priorities in A-interface. Impact on Abis interface GSM-WCDMA Interworking has an impact on the following messages: .
UTRAN CLASSMARK CHANGE (UE -> BSS)
.
SYSTEM INFORMATION TYPE 2quater (BSS -> UE)
.
MEASUREMENT INFORMATION (BSS -> UE)
.
INTER SYSTEM TO UTRAN HANDOVER COMMAND (BSS -> UE)
.
SYSTEM INFORMATION TYPE 3 (BSS -> UE)
.
CHANNEL ACTIVATION (BSC -> BTS)
.
SACCH INFO MODIFY (BSC -> BTS)
.
HANDOVER FAILURE (UE -> BSS)
Impact on Gb interface No impact. Impact on Q3 and XML interfaces The BSC supports Q3 and XML interfaces for GSM-WCDMA interworking related parameters and counters.
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2.10
Impact on capacity From 3GPP Release 4 onwards, a serving GSM cell can send a cell information on a maximum of 96 neighbour cells (includes cells of GSM, WCDMA RAN using FDD, and WCDMA RAN using TDD) to a user equipment (UE).
2.11
Interworking with other features BSC-Initiated Traffic Reason Handover (TRHO) When deciding on an initiation of a BSC-Initiated TRHO, both the completed BSC-Initiated TRHOs and the load decrease of the serving cell due to an inter-system handover (ISHO) are taken into consideration. Correspondingly, when deciding on an initiation of an ISHO, both the completed ISHOs and the load decrease of the serving cell due to a BSCInitiated TRHO are taken into consideration. Both of the above-mentioned conditions are valid, when a new BSCinitiated TRHO or ISHO are evaluated after either a previous TRHO or ISHO, but before a load level is evaluated again. For more information, see Advanced Multilayer Handling under Feature descriptions/Radio network performance in the PDF view. GPRS GPRS affects the visibility of the ISHO parameters which are defined only for GPRS-capable MSs. The GPRS threshold to search WCDMA RAN cells parameter is not influenced by the GPRS and is therefore visible if only ISHO is enabled. For more information, see GPRS/EDGE System Feature Description under Feature descriptions/Data in the PDF view and BSS Radio Network Parameter Dictionary under Reference/Parameters in the PDF view. Common BCCH Control Common BCCH Control decreases the maximum number of neighbour GSM cells and BCCH allocation list (BA) frequencies. For more information, see Common BCCH Control in BSC under Feature descriptions/Radio network performance in the PDF view.
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Inter-System Network-Controlled Cell Re-selection GSM-WCDMA Inter-System Handover application software has to be activated before you can use Inter-System Network-Controlled Cell Reselection. For more information, see Inter-System Network-Controlled Cell Reselection under Feature descriptions/Data in the PDF view. Dual Transfed Mode (DTM) If IS-NCCR is activated and the DTM-capable mobile is in a DTM cell, it is possible that both SGSN and MSC send service priority information. The BSC selects the service priority to be followed. For more information, see Inter-system handover in Dual Transfer Mode under Feature descriptions/ Data in the PDF view. IMSI-based Handover GSM-WCDMA Inter-System Handover application software has to be activated before IMSI-based Handover (IBHO) can be used to evaluate inter-system handovers from GSM BSS to WCDMA RAN. For more information, see IMSI-based Handover under Feature descriptions/Radio network performance in the PDF view. GSM - TD-SCDMA Interworking A BTS/SEG can have either adjacent WCDMA RAN cells or adjacent TDSCDMA RAN cells regardless of the fact that both GSM-WCDMA InterSystem Handover application software and GSM - TD-SCDMA idle mode support application software are active in the BSC. It is not recommended to use GSM-WCDMA Interworking and GSM - TDSCDMA Interworking at the same time in the same BSC. For more information, see GSM - TD-SCDMA Interworking under Feature descriptions/Radio network performance in the PDF view.
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3
Planning GSM-WCDMA Interworking
3.1
GSM-WCDMA cell re-selection in idle state The main principle in implementing the WCDMA RAN selection handling is to enable an operator to define the WCDMA RAN measurement offsets and cell re-selection thresholds that are sent to the user equipment (UE) in the SYSTEM INFORMATION messages. A dual mode GSM/WCDMA UE is able to perform a cell re-selection from the GSM network to the WCDMA RAN network in the idle state if the UE is informed about the WCDMA RAN cells. The cell re-selection is based on the parameters that the BSC sends to the UE. When planning a re-selection from GSM to WCDMA RAN in idle mode and packet idle mode, the following must be taken into account: .
A WCDMA base station (WBTS) must be defined as a neighbour WCDMA RAN cell for the BTS in the BSC.
.
The following BTS parameters must have appropriate values before mobile-originated cell re-selection to WCDMA RAN is possible: .
threshold to search WCDMA RAN cells
.
fdd and tdd cell reselect offset
.
minimum fdd threshold
The BTS parameter threshold to search WCDMA RAN cells defines a threshold value for WCDMA RAN cell measurements in the serving GSM cell. The running average of received signal level (RLA_C) of the serving GSM cell has to be above or below the threshold value set with this parameter before dual mode GSM/WCDMA mobiles perform adjacent WCDMA RAN cell measurements in the serving GSM cell. With this parameter it is also possible to totally deny or allow WCDMA RAN cell measurements in the serving GSM cell.
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The BTS parameter fdd and tdd cell reselect offset defines WCDMA RAN cell re-selection offset in the serving GSM cell. The measured value of received signal code power (RSCP) of the WCDMA RAN cell has to exceed the RLA_C of the serving GSM cell, and all suitable GSM cells by this offset value before the dual mode GSM/WCDMA UE can make a cell re-selection from the serving GSM cell to the WCDMA RAN cell. This BTS parameter minimum FDD threshold defines a threshold value for measured Ec/No which must be exceeded before dual mode GSM/ WCDMA mobile is allowed to make a cell re-selection from the serving GSM cell to the WCDMA RAN cell. The BSS20477:CPICH RSCP Based Criterion for 2G to 3G Cell Reselection application software introduces two additional parameters for cell re-selection: .
minimum RSCP threshold
.
minimum FDD threshold offset
The minimum RSCP threshold parameter defines a minimum threshold for received signal code power (RSCP) for the cell re-selection from the serving GSM cell to a WCDMA RAN cell. This parameter prevents the dual mode mobile (3GPP Release 5 onwards) from entering a WCDMA RAN cell that has too weak measured RSCP value. The parameter minimum fdd threshold offset defines a negative offset to the minimum Ec/No value for newer dual mode mobiles (3GPP Release 5 onwards). When minimum fdd threshold offset is used, the (Ec/No) WCDMA RAN coverage with a sufficient quality appears larger for the newer dual mode mobiles that set the minimum threshold also for RSCP in their cell re-selection algorithm from GSM to WCDMA RAN. This way, it is possible to avoid a continuous cell re-selection between GSM and WCDMA RAN for the older dual mode mobiles, while the newer dual mode mobiles can be served near the borders of the WCDMA RAN cell. The older dual mode mobiles still use minimum Ec/No threshold defined with the minimum fdd threshold parameter. The WCDMA RAN cell re-selection parameters are broadcast in the SYSTEM INFORMATION Type 2quater message. Normally the WCDMA RAN cell re-selection parameters are set so that the dual mode mode GSM/WCDMA UE makes cell re-selection from GSM to WCDMA RAN whenever there is a suitable WCDMA cell available.
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GSM
GSM
GSM
GSM
WCDMA
WCDMA UE idle mode camping WCDMA
GSM
WCDMA
GSM
UE returns back to WCDMA coverage area and makes cell reselection to WCDMA because WCDMA is given higher priority than GSM
Figure 3.
Example of UE idle mode camping in UTRAN
List of WCDMA RAN cells that are candidates for cell re-selection are broadcast in the SYSTEM INFORMATION Type 2quater message. The following set is repeated for every neighbour WCDMA RAN cell: .
WCDMA downlink carrier frequency
.
downlink transmission diversity
.
scrambling code
Note that the parameters required to determine the WCDMA RAN cell's suitability are broadcast on the BCCH of the WCDMA RAN cell. A UE may start re-selection towards the WCDMA RAN cell before decoding the BCCH of the WCDMA RAN cell. This leads to a short interruption of service, if the WCDMA RAN cell is not suitable. After the UE has reselected a GSM cell from a WCDMA RAN cell there is a five-second pause to the cell re-selection to WCDMA RAN. Algorithm for cell re-selection You can control the measurements for re-selection with the parameter threshold to search WCDMA RAN cells . The parameter defines a threshold and also indicates whether these measurements are performed when the running average of received signal level (RLA_C) of the serving GSM cell is below or above the threshold.
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If the neighbour cell list broadcast from the BSC to the UE contains information on the WCDMA RAN cells, the UE updates the value RLA_C for the serving cell and each of the at least six strongest non-serving GSM cells at least every five seconds. The UE re-selects a suitable WCDMA RAN cell, if all of the following criteria are met for a period of five seconds: 1.
its measured received signal code power (RSCP) value exceeds the value of RLA_C for the serving cell and all of the suitable nonserving GSM cells by the value fdd and tdd cell reselect offset.
2.
its measured Ec/No value is equal to or greater than the value minimum fdd threshold - minimum fdd threshold offset.
3.
its measured RSCP value is equal to or greater than FDD RSCP threshold (from 3GPP Rel. 5 onwards). Where: . Ec/No (the ratio of energy per modulating bit to the noise spectral density) and RSCP are the measured quantities. . fdd and tdd cell reselect offset and minimum FDD threshold are broadcast on the BCCH of the serving cell. . minimum FDD threshold offset and minimum RSCP threshold are optional parameters that are broadcast on the BCCH of the serving cell if the CPICH RSCP Based Criterion for 2G to 3G Cell Re-selection application software product is activated. . FDD RSCP threshold is the minimum acceptable value for RSCP. . The UE calculates the value for FDD RSCP threshold with the formula minimum RSCP threshold - min((P_MAX - 21 dBm), 3 dB), if minimum RSCP threshold is broadcast on the serving cell. Else the UE defines the value for FDD RSCP threshold by using the minimum required RX level and the UE's maximum allowed TX power level in the WCDMA RAN cell, if these parameters are available. Otherwise the UE uses the default value of the minimum RSCP threshold parameter.
In case a cell re-selection occurs within the previous 15 seconds, the UE increases the value of fdd and tdd cell reselect offset by 5 dB. If more than one WCDMA RAN cell fulfills the above criteria, the UE selects the WCDMA RAN cell with the greatest RSCP value.
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WCDMA measurements are started when a certain RX level is achieved in the serving cell.
Dual mode UE starts WCDMA measurements when the running average signal level (RLA_C) is below or above the threshold value Qsearch_I (threshold to search WCDMA RAN cells).
WCDMA neighbour cell’s RSCP is compared to the RX level of the serving GSM cell and the neighbour GSM cells.
Dual mode UE checks if the RSCP of some neighbour WCDMA cell has exceeded the RLA_C of the serving GSM cell and the neighbour GSM cells with the parameter fdd and tdd cell reselect offset for a period of five seconds. CPICH RSCP > RLA_C + FDD_Qoffset
WCDMA neighbour cell’s Ec/No has to fulfill the minimum requirement. Ec/No is a good estimate for downlink quality.
Dual mode UE checks that the WCDMA cell ‘s Ec/No has exceeded the minimum fdd threshold for a period of five seconds.
WCDMA neighbour cell’s RSCP has to fulfill the minimum requirement. The uplink quality is strongly dependent on RSCP.
CPICH Ec/No >= FDD_Qmin-FFD_Qmin_Offset
Dual mode UE checks that the WCDMA cell’s RSCP has exceeded the FDD RSCP threshold for a period of five seconds. CPICH RSCP > = FDD_RSCP_threshold
Dual mode UE makes a cell re-selection from the GSM cell to the WCDMA cell.
Figure 4.
Cell re-selection process (Non-GPRS/EDGE capable phone)
UE controlled inter-system cell re-selection for PS connection When the WCDMA FDD NCCR enabled parameter has been disabled, a dual mode GSM/WCDMA UE can initiate and control inter-system cell reselections from GPRS/EDGE to WCDMA RAN for a PS connection according to the WCDMA RAN related idle state parameters received from BCCH/CCCH when the UE is in the packet transfer mode. The UE uses the same parameters and algorithm for inter-system cell re-selections as in the packet idle mode.
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3.2
GSM-WCDMA handover process Nokia GSM-WCDMA Inter-System Handover application software includes handovers for coverage and load reasons. The measurement parameters of the WCDMA RAN neighbour cells are sent to the dual mode GSM/WCDMA UEs in the MEASUREMENT INFORMATION messages. The BSC compares the processed measurement results (averages) with the relevant handover thresholds. If preprocessing is used in the BTS, the comparison takes place whenever the BSC receives measurement results from the BTS. The HO threshold comparison includes, for example, the evaluation of the uplink/downlink level, quality and interference, and MSBS distance evaluation. The BSC performs the evaluation of a handover from GSM to WCDMA RAN after the evaluation of a downlink level handover. The priority order of the handovers is based on the HO threshold comparison in the SDCCH and TCH channels. For more information, see BSC handovers in RF Power Control and Handover Algorithm under Functional descriptions/Radio network performance in the PDF view. The following prerequisites must be fulfilled in order to enable an intersystem handover from GSM to WCDMA RAN: .
The target cell candidates (WBTSs) are defined as neighbour WCDMA RAN cells for the serving GSM cell in the BSC.
.
The UEs (which are in the dedicated state) are allowed to measure the neighbour WCDMA RAN cells of the serving GSM cell. You can define the measuring threshold with the parameter threshold for multi-RAT MS.
.
The UE has sent the neighbour WCDMA RAN cell measurements to the BSC. You can control the measurement sending by the number of measured FDD cells (FDMR) parameter.
.
Early classmark sending is allowed for UEs in the serving GSM cell. You can control the early classmark sending with the parameter early sending indication. For more information, see Base Transceiver Station Handling in BSC under Reference/Commands/MML commands in the PDF view and BSS Radio Network Parameter Dictionary under Reference/ Parameters in the PDF view.
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.
The UE has sent the UTRAN CLASSMARK CHANGE message to the BSC. A dual mode GSM/WCDMA UE sends a UTRAN CLASSMARK CHANGE message to the BSC if the early classmark sending is allowed in the serving GSM cell. The content of the message is required by the RNC which controls the target WCDMA RAN cell.
.
The connection-specific penalty timer for inter-system handover attempts is not running.
The BSC initiates an inter-system handover attempt to the WCDMA RAN if: .
A neighbour WCDMA RAN cell is available (coverage). The cell-specific penalty timer does not exist in the BSC for the WCDMA RAN cell. Ec/No measured by the UE has to exceed the handover threshold minimum CPICH Ec/Io level.
.
Traffic load of the serving GSM cell exceeds the threshold (load). You can define the load threshold with the min traffic load for speech call parameter. The use of load threshold is also influenced by the service priority which is sent by the MSC. For more information, see Support of service priorities in A-interface. The procedure for the traffic load checking is similar to the BSCinitiated Traffic Reason Handover. The BSC initiates only as many inter-system handovers as the number of ongoing calls in the serving GSM cell is over the traffic load threshold. This means that the serving GSM cell is not emptied into the WCDMA RAN.
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Handover Triggering Thresholds set in the BSC. Inter-RAT measurements start if the RXLEV of the serving cell is above or below the given threshold Qsearch_C
MS measures the UTRAN cells. If they are defined as neighbours, measurements are done during idle periods.
Inter-system handover decision is done if load of the serving cell exceeds load threshold and there are WCDMA RAN cell(s) whose measured Ec/No level exceeds CPICH Ec/No threshold. Load ofthe serving GSM cell is ignored, if the inter-system handover is triggered because of GSM coverage reason or because of service priority. . The BSC selects the target WCDMA RAN cell based on the measurement result.
Handover request is sent to the MSC.
Figure 5.
GSM-WCDMA inter-system handover process
You can prevent the MSs from sending measurement reports of the neighbour WCDMA RAN cell, and thereby also inter-system handovers from a GSM cell to WCDMA RAN, by adjusting the value of the following parameter: .
number of measured FDD cells (FDMR) is set to value 0.
Inter-system handover example The parameter min traffic load for speech call has the value 60 (60 %) and the parameter minimum CPICH Ec/Io level has the value 18 (-15 dB). In addition, the BSC has received and averaged measurement results for the neighbour WCDMA RAN cell and calculated the traffic load of the serving GSM cell:
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1.
The traffic load of the serving GSM cell is 45 % and the averaged Ec/ No of the WCDMA RAN cell has the value 18 (the averaged Ec/Io level is smaller than -15.5 dB). In this case the inter-system handover attempt is not possible due to too low traffic load and low signal quality.
2.
The traffic load of the serving GSM cell is 45 % and the averaged Ec/ No of the WCDMA RAN cell has the value 19 (the averaged Ec/Io is equal or greater than -15 dB). In this case the inter-system handover attempt is not possible due to too low traffic load.
3.
The traffic load of the serving GSM cell is 65 % and the averaged Ec/ No of the WCDMA RAN cell has the value 19 (the averaged Ec/Io is equal or greater than -15 dB). In this case, the inter-system handover attempt is possible.
3.2.1
Inter-System Direct Access Inter-System Direct Access to the WCDMA RAN The purpose of BSS11107: GSM-WCDMA Inter-System Direct Access is to enable the BSC to hand a UE directly from the SDCCH channel of a serving cell to the WCDMA RAN. GSM-WCDMA Inter-System Direct Access is application software in the BSC. Idle state measurement parameters of the WCDMA RAN neighbours are sent to the dual mode GSM/WCDMA UEs in the SYSTEM INFORMATION Type 2quater messages. These parameters are also used on the SDCCH channel for the Inter-System Direct Access. The following conditions have to be fulfilled before the handover attempt can be initiated by the BSC: .
GSM-WCDMA Inter-System Handover application software has to be enabled.
.
GSM-WCDMA Inter-System Direct Access application software has to be enabled with the parameter inter-system direct access enabled.
.
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The BSC must have received an indication from the UE about its WCDMA RAN capability in the CLASSMARK CHANGE message. The UE has to be FDD capable. The message must already have been received on the SDCCH.
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.
The BSC has received the service priority with the value 'should' from the MSC. Note that inter-system direct access begins only if the service priority is set to ‘should’. For more information about the service priority, see Support of service priorities in A-interface.
.
The UE must have already received information about the adjacent WCDMA RAN cells from the BSC on the SDCCH.
.
The MSC must support the sending of the Service Handover information element in the ASSIGNMENT REQUEST message. The value of the service priority has to be set to SHOULD. For more information on service priority, see Support of service priorities in Ainterface.
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The BSC has to have received measurement reports of the WCDMA RAN adjacent cell(s) already on the SDCCH.
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The Ec/No of the target WCDMA RAN cell has to be over the InterSystem Direct Access threshold direct access EC/IO threshold.
Unsuccessful Inter-System Direct Access to the WCDMA RAN After an unsuccessful Inter-System Direct Access attempt, the call is cleared.
3.2.2
Inter-System handover penalties and timers Connection-specific penalty timers after unsuccessful inter-system handover attempt from GSM to WCDMA RAN The BSC controls connection-specific inter-system handover requests and attempts in the serving GSM cell with the handover control parameters min int between HO req and min int between unsucc HO attempt. For more information, see Interval between handovers and handover attempts in RF Power Control and Handover Algorithm under Functional descriptions/Radio network performance in the PDF view and Handover Control Parameter Handling (command group EH) under Reference/ Commands/MML commands in the PDF view. In addition, when the BSC initiates the inter-system handover attempt to a WCDMA RAN cell but fails, the connection-specific penalty timer for the target WCDMA RAN cell is applied. That is, the connection in question is not allowed to initiate an inter-system handover attempt to a penalised WCDMA RAN cell until the timer expires. The duration of the penalty can be set with the min interval between unsucc ISHO attempt parameter.
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Cell-based penalty timers after unsuccessful handovers from GSM to WCDMA RAN Cell-based penalties are used in order to avoid unnecessary handover attempts from GSM to WCDMA RAN on a serving GSM cell level. Unsuccessful handover attempts from the serving GSM cell to WCDMA RAN cell indicate that the WCDMA RAN cell in question is loaded. Thus, it is not sensible to initiate handovers from the serving GSM cell to the loaded WCDMA RAN cell. When a certain ratio of unsuccessful inter-system handover attempts in a predefined time gap is exceeded in the serving GSM cell, the BSC gives a cell-based penalty for the target WCDMA RAN cell. That is, none of the connections in that GSM cell are allowed to initiate an inter-system handover attempt towards the penalised WCDMA RAN cell. Inter-system handover attempts from other GSM cells towards the penalised WCDMA RAN cell are allowed. The ratio of unsuccessful inter-system handover attempts is defined with the triggering ratio for WCDMA RAN cell penalty (TRW) parameter. Unsuccessful inter-system handover attempts are calculated from the time gap, which is defined with the penalty trigger measurement period (PTMP) parameter. The penalty time is defined with the WCDMA RAN cell penalty time (WCP) parameter. The maximum number of simultaneous cell-based penalties is 16. Cellbased penalties can be disabled in the BSC by setting the penalty trigger measurement period parameter to 0. Connection-specific penalty timers after successful Inter-system handover from WCDMA RAN to GSM An inter-system handover from WCDMA RAN to GSM indicates high load in the WCDMA RAN. When a handover from WCDMA RAN to GSM is detected, the BSC is not allowed to initiate a handover back to WCDMA RAN for the same connection during the 30-second penalty time. Service-area-based penalty timers after successful handovers from WCDMA RAN to GSM Service-area-based penalties are used to avoid unnecessary handover attempts from GSM to WCDMA RAN on the BSC level. Handovers from WCDMA RAN to GSM indicate that the WCDMA RAN service area where the handover is coming from is loaded. Therefore it is not sensible to initiate handovers from GSM to the loaded WCDMA RAN service area.
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When a certain number of successful inter-system handovers in a predefined time gap is exceeded in the BSC, the BSC gives a servicearea-based penalty for the source WCDMA RAN service area. That is, none of the connections in that BSC are allowed to initiate inter-system handovers towards the penalised WCDMA RAN service area. The number of successful inter-system handovers is defined with the parameter triggering threshold for service area penalty. The time gap from where the number of successful inter-system handovers are calculated, is defined with the penalty trigger measurement period parameter. The penalty time is defined with the service area penalty time parameter. The maximum number of simultaneous service-area-based penalties is 16. Service-area-based penalties can be disabled in the BSC by setting the penalty trigger measurement period parameter to 0. Supervision of an inter-system handover attempt procedure GSM timer T3121 parameter defines the maximum supervision time for an inter-system handover procedure from GSM to WCDMA RAN in the source BSC. Sending an INTER SYSTEM TO UTRAN HANDOVER COMMAND message to the UE starts this connection-specific T3121 timer. It is normally stopped when the UE has correctly seized the WCDMA RAN channel(s). The purpose of the timer is to keep the old channels for a sufficiently long time in order to enable the UE to return to the old channels, and to release the channels if the UE is lost. For more information on the timer parameter, see PAFILE Timer and Parameter List under Reference/Parameters in the PDF view.
3.2.3
Support of service priorities in A-interface The BSC handles service priority indication in the ASSIGNMENT REQUEST and HANDOVER REQUEST messages. The indication informs the BSC whether the connection in question:
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should be direct accessed or handed over to the WCDMA RAN. WCDMA RAN is preferred. That is, the Handover Algorithm should initiate inter-system direct access or inter-system handover to the WCDMA RAN as soon as the WCDMA RAN coverage is available.
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should not be direct accessed or handed over to the WCDMA RAN. Neither inter-system direct access nor inter-system handover to the WCDMA RAN should be performed. The BSC is not allowed to initiate inter-system direct access from the GSM to the WCDMA RAN. Inter-system handover to the WCDMA RAN is allowed only if the load of the serving GSM cell is over the threshold min traffic
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load for speech call. However, the serving GSM cell load and the load threshold min traffic load for speech call are ignored, if
other GSM cells are not available in the inter-system handover even if the load of the source cell is below the load threshold.
3.2.4
.
shall not be direct accessed, or handed over to the WCDMA RAN. The GSM is preferred and WCDMA RAN is forbidden. That is, the BSC is not allowed to initiate inter-system direct access from the GSM to the WCDMA RAN.
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is not in use, if GSM-WCDMA Inter-System Handover application software is activated in the BSC, but the BSC does not receive the service priority indication, because the MSC does not support its sending. The BSC behaves as if the service priority is not in use. In addition, if the BSC receives service priority indicating something other than ‘should’, ‘should not’ or ‘shall not’, the BSC behaves like the service priority is not in use. When the service priority is 'not in use' in the BSC, the inter-system direct access to the WCDMA RAN is not allowed. Inter-system handover to the WCDMA RAN is allowed only if the load of the serving GSM cell is over the threshold min traffic load for speech call, or for a GSM coverage reason.
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If GSM-WCDMA Inter-System Handover application software is not activated, the BSC sets service priority as ‘disabled’.
WCDMA RAN cell measurements for GSM-WCDMA inter-system handover WCDMA RAN cell measurement and reporting The dual mode GSM/WCDMA UE is able to measure the signal levels of the neighbour WCDMA RAN cells when it is in idle state and camped on a GSM cell. The information of the cells is sent to the UE in SYSTEM INFORMATION type 2 quater (SI 2quater) messages. The SI 2quater messages are sent to the UE only if the serving GSM cell has WCDMA RAN neighbour cells. The message is sent on the BCCH and it may contain more than one instance. The dual mode GSM/WCDMA UEs are allowed and also forced to measure the WCDMA RAN neighbours in idle state, if the RXLEV of the serving GSM cell is below or above the threshold threshold to search WCDMA RAN cells.
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The GPRS/EDGE capable dual mode GSM/WCDMA UEs are allowed and also forced to measure the WCDMA RAN neighbours in idle state if the RXLEV of the serving GSM cell is below or above the threshold GPRS threshold to search WCDMA RAN cells when IS-NCCR is in use or both NCCR and IS-NCCR are inactive. Measurement parameters of the WCDMA RAN neighbours are sent to a dual mode GSM/WCDMA UE in the MEASUREMENT INFORMATION (MI) message. The UE is allowed and also forced to measure and report the WCDMA RAN neighbours in dedicated state if the RXLEV of the serving GSM cell is below or above the threshold threshold for multiRAT MS.
The network sends the MI message to the UE on the SACCH. If not all information fits into one message, the remaining information is sent in other instances of this message. The neighbour cell list is based on the SI 2quater message and built by the UE. It is used for reporting when the UE enters the dedicated state, until the UE has received all instances of MEASUREMENT INFORMATION messages that contain "3G Neighbour Cell Description" information element. Information about WCDMA RAN cells is included in SI 2quater and MI messages only if the cells are defined as neighbour WCDMA RAN cells for the serving GSM cell. The dual mode GSM/WCDMA UEs are able to find and identify a WCDMA RAN cell by the following information: .
WCDMA downlink carrier frequency
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scrambling code
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downlink transmission diversity
You can define the maximum number of the neighbour WCDMA RAN cells that are included by the UE in the list of the strongest cells in a measurement report which is sent to the radio network. You can do this with the parameter number of measured fdd cells. The UEs are ordered to report to the BSC by using Ec/Io as the measurement quantity.
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Ec/Io (dB) Ec/No (class)
Figure 6.
-24 -23.5 -23 -22.5 0
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Measurement quantity is EC/lo (reported as Ec/No classification value)
The number of WCDMA RAN cells from which the UE is able to perform neighbour cell measurements depends on the number of frequencies used. According to the 3GPP standard the allowed reporting time is increased by five seconds for each additional WCDMA RAN frequency in the neighbour cell list. However, multiple WCDMA RAN cells on the same frequency in the neighbour cell list do not increase the allowed reporting time. This means that if there are WCDMA RAN neighbours in more than one WCDMA RAN frequency, there are going to be delays in the neighbour cell reporting. WCDMA RAN neighbour cell reporting enhancement The BSC makes inter-system handover and inter-system network controlled cell re-selection decisions based on the measurement reports it receives from the mobile. A fdd reporting threshold parameter defines the CPICH Ec/No threshold for adjacent WCDMA RAN cell reporting in the serving GSM cell. When measurement reporting is controlled solely with this parameter, the downlink quality only is taken into account. This may lead to a failure of ISHO or IS-NCCR because of a poor uplink quality. The uplink quality is strongly dependent on the RSCP level. The BSS20858:WCDMA Neighbour Cell Reporting Enhancement application software product introduces a parameter fdd reporting threshold 2 which defines the CPICH RSCP threshold for adjacent WCDMA RAN cell reporting in the serving GSM cell. 3GPP Rel 5 and newer dual mode mobiles supporting this parameter do not send measurement reports of the neighbour WCDMA RAN cells whose CPICH RSCP value is below the threshold defined by the fdd reporting threshold 2 parameter. Thus ISHO and IS-NCCR to target WCDMA RAN cells with poor uplink quality can be avoided.
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Bookkeeping and averaging of the CPICH Ec/No of the neighbour WCDMA RAN cell The BSC averages the signal level of the neighbour WCDMA RAN cells (ECNO_NCELL(n)) only at the time when the averaged results are needed for the decision procedure. The averaging procedure is able to take into account a maximum of 32 most recent measurement samples per neighbour WCDMA RAN cell and maintain the last 32 measurement samples of up to 32 neighbour WCDMA RAN cells per a serving GSM cell. The measured value replaces RXLEV in the measurement reports. Averaging procedure of the CPICH Ec/No of the neighbour WCDMA RAN cell The averaging procedure is controlled by the following parameters: .
adjacent WCDMA RAN cell averaging window size determines the
averaging window size which is used for calculating averaged values from downlink (neighbour WCDMA RAN cell) signal level measurements for handover threshold comparison and decision. The range of the averaging window size is from 1 to 32 SACCH multiframe periods, where the value 1 means that there is basically no averaging at all. .
number of WCDMA RAN zero results indicates the maximum number
of zero results that can be omitted when the measurement results of the neighbour WCDMA RAN cells are averaged. The range of the parameter is from 0 to 32 zero results. .
WCDMA RAN all cells avg indicates whether the measurement
results are averaged for every neighbour WCDMA RAN cell (the value is 'yes') or only for the maximum of three cells which are the best according to the last measurement sample (the value is 'no'). The averaging parameters are controlled on a cell-by-cell basis. The BSC may average the signal level of the neighbour WCDMA RAN cells already after the first received measurement sample. Example The value of the parameter adjacent WCDMA RAN cell averaging window size (UAWS) is 8 and the value of the parameter number of WCDMA RAN zero results (UNOZ) is 2, and the BSC has received eight measurement results from the neighbour WCDMA RAN cell at SACCH multiframe k:
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AV_ECNO_NCELL(n) = 1/8 (ECNO_NCELL(n)(k) + ECNO_NCELL(n)(k1) + ... + ECNO_NCELL(n)(k-7)) If the result k-1 was zero, the effective averaging window size would be 7: AV_ECNO_NCELL(n) = 1/7 (ECNO_NCELL(n)(k) + 0 + ECNO_NCELL(n) (k-2) + ... + ECNO_NCELL(n)(k-7)) Example The value of the parameter adjacent WCDMA RAN cell averaging window size (UAWS) is 8 and the value of the parameter number of WCDMA RAN zero results (UNOZ) is 7, and the BSC has received one measurement result (CPICH_Ec/No 40) from the neighbour WCDMA RAN cell. In this case the average is: 40 / (UAWS - UNOZ) = 40 / (8-7) = 40. Example The value of the parameter adjacent WCDMA RAN cell averaging window size (UAWS) is 8 and the value of the parameter number of WCDMA RAN zero results (UNOZ) is 7, and the BSC has received five measurement results (CPICH_Ec/No 40, 42, 39, 40, and 43) from the neighbour WCDMA RAN cell (therefore there are three measurement results missing and they are fewer than the value of the parameter UNOZ; the number of missing results is subtracted from the UAWS parameter). In this case the average is (40 + 42 + 39 + 40 + 43) / (8-3)= 41. Example The value of the parameter adjacent WCDMA RAN cell averaging window size (UAWS) is 12 and the value of the parameter number of WCDMA RAN zero results (UNOZ) is 5, and the BSC has received three measurement results (CPICH_Ec/No 40, 42, and 43) from the neighbour WCDMA RAN cell (therefore there are nine measurement results missing, and that is more than the value of the UNOZ parameter; the value of the UNOZ parameter is subtracted from the value of the UAWS parameter). In this case the average is (40 + 42 + 43)/(12-5) = 17.
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Averaged result of the Ec/No of the neighbour WCDMA RAN cell The following correspondence exists between the measurement results (signal level of the neighbour WCDMA RAN cell: ECNO_NCELL(n)), the averaging parameters, and the averaged result. The averaged result is used in the equations for handover threshold comparison and decision. measurement result
averaging parameters
averaged result
ECNO_NCELL(n)
adjacent WCDMA RAN cell averaging window size
AV_ECNO_NCELL(n)
number of WCDMA RAN zero results all adjacent WCDMA RAN cells averaged
3.3
UE camping on a 3G cell after a call release Generally voice calls initiated in UMTS (3G) are handed over to GSM (2G). When a call is terminated in a GSM cell, the UE is directed through a lengthy process to camp as quickly as possible on a GSM (2G) cell whose channel has just been released. The UE performs LAU/RAU (Location Area Update/Routing Area Update) in 2G. With default 3G camping, another LAU/RAU is needed for a cell re-selection to UMTS. This process requires a lot of signalling update. When the BSS20132: Mobile Specific Channel Release Message application software product is active, it is possible to remove unnecessary signalling and delay in service access by directing mobiles straight to a WCDMA RAN cell after a call release in GSM without performing LAU/ RAU procedures on GSM side. The BSC attaches an optional information element “Cell selection indicator after release of all TCH and SDCCH” to the CHANNEL RELEASE message. In this information element, the BSC identifies the strongest WCDMA RAN cell according to the measurement reports the UE sent before the channel release. The BSC sends direct camping information to all dual mode mobiles (3GPP Rel 6 onwards) when UMTS coverage is available and the UE reports at least one WCDMA RAN neighbour cell. This WCDMA RAN neighbour cell is indicated in the CHANNEL RELEASE message as a target cell for idle mode camping. If the UE reports more WCDMA RAN neighbour cells, several alternative cells are indicated as a target cell for idle mode camping.
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The figure Cell selection in idle mode camping illustrates a process of direct camping of the user equipment on a 3G cell. Voice call setup
WITHOUT
3G IDLE
Handover to GSM
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2G-camping after call terminates
Default 3G camping
2G LAU/RAU 3G LAU/RAU
3G IDLE Listening to paging
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3G IDLE Channel release: "directly camp on 3G"
Figure 7.
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Cell selection in idle mode camping
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4
Implementing GSM-WCDMA Interworking overview Before you start Check that all network elements involved are GSM-WCDMA Interworking capable. For more information, see Activating and Testing BSS10101, BSS11107, BSS20477, BSS20858 and BSS20132: GSM-WCDMA Interworking under Test and activate/Radio network performance in the PDF view. With the NetAct Radio Access Configurator tools it is possible to manage inter-system adjacencies and the related parameters. For more information, see Managing Adjacencies in Nokia NetAct Product Documentation. You can activate GSM-WCDMA Interworking at any time.
Steps 1.
Define the incoming and outgoing adjacencies (EAE).
2.
Check that ISHO_SUPPORT_IN_BSC is activated in the BSC (WOS).
3.
Activate Inter-system handover and UMTS changes in MSC. For more information, see Feature 1260: Inter-system handover and UMTS changes in MSC in Nokia MSC/HLR Feature Activation Manuals. Note that for Inter-PLMN handovers, Feature 1168: Multiple PLMN and Inter-PLMN handover support in MSC must be in use. For more information, see Feature 1168: Multiple PLMN and Inter-PLMN Handover Support in MSC in Nokia MSC/HLR Feature Activation Manuals.
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4.
Test the activation in BSC. For detailed information, see Activating and Testing BSS10101, BSS11107, BSS20477, BSS20858 and BSS20132: GSM-WCDMA Interworking under Test and activate/Radio network performance in the PDF view.
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