Restriction on Number of Cells in SIB

Technical Note TS-RNC-SW-046

Restriction on number of cells in SIB11/12 due to inconsistency problem in 3GPP TS 25.331 Radio Controllers WCDMA RNC RN4.0, RN5.0, RN6.0 This document contains following type of information Informative

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Preventive Corrective Additional categorization Urgent Security Release Upgrade SW Update Information is classified as Internal Public

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Customer Specific

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Table of Contents 1. 2. 3. 4. 5.

Keywords........................................................................................................................................3 Summary ......................... ............................ ............................ ............................ ........................... 3 Detailed description........................................................................................................................3 Solution / Instructions ............................ ........................... ........................... ................................... 4 References ............................ ............................ ............................ ............................. .................... 4

Contact: Contact your local Nokia Siemens Networks support

Summary of changes: 23.12.2004 23.12.2004 11.01.2005 11.11.2005 27.06.2006 27.06.2006

1.0 1.1 2.0 3.0

18.09.2006 28.02.2007 28.02.2007 02.08.2007 02.08.2007 20.01.2009 11.12.2009 26.01.2011 26.09.2011 30.09.2011 30.09.2011

3.1 3.2 4.0 5.0 6.0 7.0 8.0 9.0

9.12.2011

10.0


The first version List of the active SW technical notes removed Updated to RN2.1 WCDMA RAN1.5 system release SW support will be discontinued TN_RNC_SW_2006_082 Software validity updated ED2 validity removed RN3.0 software validity added RN4.0 SW validity checked Removed support for RN2.2 Removed Support for RN3.0 Added RN6.0 support. Cover page updated, reference added and SIB12 restriction restricti on added. Added reference to PRFILE Descriptions document document for PRFILE RN50_MAINT_11. LTE neighbor cell information added also, SIB11bis data added and other modifications.


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Purpose This document contains generic information about products. These can be instructions that explain problem situations in the field, instructions on how to prevent or how to recover from problem situations, announcements about changes or preliminary information as requirements for new features or releases.

1. KEYWORDS RNC, Neighbour cell, RRC, SIB11, SIB12, SIB11bis

2. SUMMARY There are limitations when sending neighbor cell information in System Information Block (SIB) type 11 and 12. SIB11 and SIB12 messages can contain information on the maximum of 96 cells, but physical size of SIB data (no more than 3552 bits) has capacity only for 47 cells. The system information block type 11bis has capacity for extra 47 cells to be used in addition to SIB11 for Rel-6 and newer UEs.

3. DETAILED DESCRIPTION 3GPP TS 25.331 Radio Resource Control (RRC) protocol specification has inconsistent requirements concerning the maximum number of neighboring cells that can be broadcasted to the UEs in the System information block 11 and 12 messages. On one hand the SIB type 11 and 12 messages can contain information on the maximum of 96 cells (32 intra-frequency cells, 32 inter-frequency cells and 32 GSM cells), but on the other hand the physical size of SIB data (no more than 3552 bits) has capacity only for 47 cells (SIB Optimization not used)/ 95 cells (SIB Optimization and the 3GPP default values for cell reselection parameters parameters are used). The system information block type 11bis has capacity for extra 47 cells /95 cells to be used in addition to SIB11 for Rel-6 and newer UEs. Maximum numbers of each type of adjacencies that can be defined for one cell in RNC radio network database are: 31 (ADJS) Intra-frequency Adjacency 48 (ADJI) Inter-frequency Inter-frequency Adjacency (max 32 ADJI with in same UARFCN) 32 (ADJG) Inter-system Adjacency • • •

RNC has following restrictions on the maximum number of neighbour cells that can be sent in SIB11/SIB 11bis. With SIB Optimization used ( PRFILE RN50_MAINT_11 enabled) a> HCS used : 84 b> HCS not used : 95 Without SIB optimizations (PRFILE RN50_MAINT_11 disabled) a> HCS used : 35 b> HCS not used : 47

When SIB Optimisation is used, the RNC does include such cell reselection parameters to SIB11/SIB11bis which have 3GPP default value. The cell reselection parameters are defined for intra-frequency, inter-frequency and inter-system (GSM) neighbours in PDDB objects ADJS, ADJI and ADJG. The default value of each cell reselection parameter in PDDB equals to the 3GPP default value. If 3GPP default values are not used for all neighbouring cells, the



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maximum number of neighbour cells is between 95 and 47 cells (HCS not used) depending on the configuration. The capacity is smaller (84/35 cells) when HCS (hierarchical cell structure) is used because of additional cell re-selection parameters. If the number of neighbouring cells exceeds the maximum limit, the NBAP interface is not able to pack the neighbour cell information into the SIB data and the scheduling of the system information blocks fails. The cell is blocked by the system and an alarm 7771 WCDMA CELL OUT OF USE (BCCH scheduling error) is reported for the cell.

3.1 LTE neighbor cell information information Neighbour LTE frequencies are sent in System Information Block (SIB) type 19 message and they do not affect neighbour cell information in System Information Block type 11, 11bis or 12 messages.

4. SOLUTION / INSTRUCTIONS INSTRUCTIONS When SIB Optimization ( PRFILE RN50_MAINT_11) is not used, NSN guarantees 47 as maximum number of neighbors with any configuration (35 if HCS is used). The limitation of 47 neighboring neighboring cells is met with the worst possible situation that is 32 Inter-frequency Inter-frequency + 15 Intra frequency neighbors (32+3 with HCS). If some other configuration is used then the number of defined neighbor cells is higher before cell goes to BL(S) and the alarm 7771 is given. This means an operator can exceed the number but then the alarm 7771 must be observed. When SIB Optimization ( PRFILE RN50_MAINT_11) is used, NSN guarantees 95 as maximum number of neighbors when the 3GPP default values for cell reselection parameters are used (84 if HCS is used). The operator can select the neighboring cells that are broadcasted to the UE in the SIB type 11, 11bis and 12 messages. That is, if the total number of neighboring cells exceeds the physical size of the SIB data, the operator can exclude specified cells (e.g. far-awayneighbors) neighbors) from the SIB type 11, 11bis and 12 messages. In this case it is not necessary to restrict the number of neighboring cells that are required for handover in CELL_DCH state of connected mode. The operator can select the neighboring cells which are included in SIB11 or SIB11bis by means of the following neighbor cell parameters: - ADJS – AdjsSIB - ADJI – AdjiSIB - ADJG – AdjgSIB SIB12 contains the cell information which is selected in SIB11and SIB11bis. The System Information Block type 11bis (SIB11bis) is introduced in 3GPP R6 and in RAN feature RU10: RAN1323 Extension of SIB11 (SIB11bis). (SIB11bis).

5. REFERENCES NA04932806: NA04932806: Serving cell information missing after SIB optimization correction activation PRFILE Descriptions (DN0948854), (DN0948854), Nokia Siemens Networks WCDMA RAN, Rel. RU20, Operating Documentation



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Restriction on Number of Cells in SIB

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