Cs irat degradation due to physical channel failure

1. RNO Case Security Level:
Case Title：How to improve CS IRAT HO due to physical channel failure
Author Kayode Banjo (K00733670)
Date 31-07-2013
Product &
Version
V900R012C01SPH510------RNC;
V200R012C00SPC400------NodeB;
Problem
Descripti
on
In A Project, a dip in CS IRAT HO was discovered on RV0561H
Alarm
Informati
on
Null
Possible
Causes
1. Missing Neighbor (2G and 3G)
2. 2G Congestion (TCH or SDCCH)
3. Poor 2G Coverage
4. Hardware and Transmission Alarm on 3G and 2G
5. Hidden Fault like UL & DL unbalance, main diversity
6. Abnormal neighbor definition
7. Parameter Conflict (BCCH, LAC and BSIC)
Analysis CS IRAT HO KPI
CS IRAT Failure was due to physical channel failure.
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Before Optimization After Optimization

2. RNO Case Security Level:
Location of the 2G Cells
RV0561B(co-site of the problematic cell), BY0002B and RV0351C had the same
BCCH and BSIC.
Solution 1. Alarms checked on both 3G and 2G site indicated no alarm.
2. Checked 2G KPI i.e TCH and SDCCH Congestion and Drop rate, the KPI is
normal.
3. Abis and A interface checked for any faulty reason, none found and it is stable.
4. Uplink and downlink imbalance and main diversity cross-checked on 2G target
cell. KPI is normal.
5. Neighbor audit carried out on 3G showed that target 2G cell that has highest
failure was 100km away which has the same BSIC and BCCH with RV0351C
(43km away from source cell), RV0561B(co-site) with different LAC area as
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RV0351C
RV0561B
BY0002B

3. RNO Case Security Level:
shown in the table below. We checked TA measurement of both BY0002B and
RV0351C, the result showed that BY0002B was overshooting to the coverage of
RV0561B thereby causing adjacent interference. After consulting 2G planning
team, find below the BSIC and BCCH replan for the target 2G cell in question,
BY0002B and after monitoring within some days, KPI improved and target was
met.
2G Parameter Info before Replaning
After replanning BY0002B
Find below the 3G to 2G performance stat of RV0561H. The action was carried out on
24/04/2013 08:00:00 and after monitoring, HO stopped handing over to the cell around
25/04/2013 08:00:00 am and the KPI improved.
Suggestio
n and
Summary
In this scenario, apart from checking any impacting alarms on both source and target cell,
parameter audit should always be carried out on both 2G and 3G most especially LAC, BCCH and
BSIC to avoid conflict in every 5days because 2G planning team made changes to these parameter
often without informing the 3G team. Even when the reason of the failures indicated “Physical
channel failure” meaning “congestion on the 2G cells or 2G cell is not available”, it may be due to
parameter conflict during decoding by the MS.
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4. RNO Case Security Level:
Attachme
nt
Reference
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