Multiple CCCH

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COPYRIGHT 2011 ALCATEL-LUCENT. ALL RIGHTS RESERVED.ALCATEL-LUCENT INTERNAL PROPRIETARY USE PURSUANT TO COMPANY INSTRUCTION

mCCCH - SonatelFeature introduction Strategy and MonitoringNnamdi E - NDE


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1. Issue Description/Analysis

2. Theoretical Overview of Solution

3. Test Strategy/Monitoring

AGENDA


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.


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Issue Description/Analysis


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Issue Description/Analysis

Issue

High Load on AGCH and PCH Channels Observed on certain LAC/Cells in Dakar City

End user Perception:

AGCH Congestion: Call establishment Failure.

PCH Congestion: Failure to connect to call Party. Mobile Subscriber cannot be reached/Voice Mail.

Proposed Solutions:

Modify Parameter BS_AG_BLKS_RES: Not recommended since issue is observed both on Paging and Access Grant at same time


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Increase AGCH/PCH capacity by Implementing mCCCH: Gains in both Access Grant and Paging Channel at the same time.

Redesign LAC to reduce Paging Load: (High risk of SDCCH Congestion after LAC Split. For scenario where Paging Load remains

above limit after mCCCH Upgrade)

Option 2 is chosen mCCCH (as first approach in order to avoid LAC Split)

Test LAC

LAC131 with current paging load 100% resulting in Discarded paging due to Congestion.

Risk

No risk identified


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Theoretical Overview


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The CCCH channel is used by:

Paging Channel (PCH): Downlink only, used to page mobiles.

Random Access Channel (RACH): Uplink only, used to request allocation of a SDCCH.

Access grant channel (AGCH): Downlink only, used to allocate a SDCCH or directly a TCH.

Notification channel (NCH): Downlink only, used to notify mobile stations of voice group and voice broadcast calls.

Only one additional CCCH is required, TS2 would be used on the same TRX than the TS0 supported BCCH+CCCH.

System Information Duplication


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, . .

Information messages sent on the both BCCHs in TS0 and TS2 are duplicated by BTS..


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TCU limitation (G2BSC) and TRX/RSL/TCU Mapping

For G2BSC, TCU can cope with the load equivalent to 4 Time Slot signalling channels (SDCCH or CCCH).

The number of SDCCH on each TCU needs to be reduced in case of multiple CCCH.

The rule should be: N_TS_CCCH + N_TS_SDCCH


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Test Strategy/Monitoring


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Test Strategy

Statistical tests (QoS analysis, and Traffic evaluation) as mandatory tests.

The planning is basically split in two phases,

first, reference tests shall be done without mCCCH feature activated and

the same tests and assessment shall be performed with mCCCH feature activated.

The high level planning is as follow:

Phase 1: Usage of a single CCCH TS (BCCH) (Reference period)

Statistical tests


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Statistical tests

The duration of each phase is minimum 1 week.

Prerequisites

Cell selection for feature activation must be done after a first analysis of CCCH traffic load in the designated LAC.

The cells with highest load on AGCH and RACH must be the preferred ones.

Also the number of discarded pagings and Immediate Assign messages may be used as a selection criterion.

LAC131 is chosen for this Test.


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Test Strategy

Paging Load 100%

Paging Status of LAC131


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Paging Failures due to Congestion/Load


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Test Strategy

Procedure

The feature must be activated in all cells inside LAC131 in order to take benefit from more resources available on CCCH.

Feature License must be enabled and ensured at OMC-R

Feature activation from OMC-R:

Step1: Select the cell to be configured with Multiple CCCH

Step2: Modify the Radio TS2 of BCCH TRX from TCH to CCCH

CCCH CONF 2


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Statistical Monitoring


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AnnexAir interface Limitation (cells in LAC131 are non combined CCCH, BS_AG_BLKS_RES = 5)

There are 9 CCCH blocks per 51 Multiframe for non-combined cells.

Then, if the parameter, BS_AG_BLK_RES = 5(meaning 4 blocks are reserved for Access Grant Channel), we have 9 5 = 4

channels available for paging (PCH)

Engineering Limit applied (from lab simulations): 2.5 Paging/PCHTherefore;

Available blocks for paging per hour:

4 PCH blocks/51Multiframe * (3600s / 235 ms) = 61,277 PCH / hour


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o e: ms s e per o or u rame

Maximum paging per hour

:2.5 paging/Block x 61,277 Blocks = 153,193 paging/hour (100%load)

When 60% engineering limit is applied

Recommended max paging per hour: 91,916 paging/hour With mCCCH 2*91,916 = 183,832paging/hr

Recommended max paging per second: 25 paging/second With mCCCH 2*25 = 50 paging/second


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Annex

Abis Interface Limitation

The Abis limitation is determined by the maximum amount of paging commands that

can be sent through the Abis interface to the cell.

An Abis can carry a paging load of 33 paging commands per second, or:

Maximum paging per hour: 118,800 paging/hour


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When mCCCH feature is enabled, the paging load on Abis is also doubled and

corresponds to 66 paging/sec, or

Maximum paging per hour: 237,600 paging/hour


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Multiple CCCH

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