irat analysis (2)

IRAT HO Failure RatioAnalysis - Huawei

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Introduction

IRAT Fail Ratio for NBH and BBH hours are consistently high in Huawei circles based on Daily NQI report.

This is one KPI which is usually dragging NQI into negative territory.

NBH – IRAT Trend BBH – IRAT Trend

14-Ja

n-11

19-Ja

n-11

24-Ja

n-11

29-Ja

n-11

3-Fe

b-11

8-Fe

b-11

13-F

eb-1

1

18-F

eb-1

10.00

2.00

4.00

6.00

8.00

10.00

12.00

DELHI CSVIRATFail-ureRate(BBH)MUMBAI CSVI-RATFailureRate(BBH)Chandigarh CSVI-RATFailureRate(BBH)

14-Ja

n-11

19-Ja

n-11

24-Ja

n-11

29-Ja

n-11

3-Fe

b-11

8-Fe

b-11

13-F

eb-1

1

18-F

eb-1

10.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

DELHI CSVIRAT-FailureRate(NBH)MUMBAI CSVI-RATFailureRate(NBH)Chandigarh CSVI-RATFailureRate(NBH)


IRAT HO Analysis Mumbai Feb 9, Feb 16 (Daily Total Stats)

Feb 9, Feb 16 raw data have been used for this analysis.

Total IRAT attempts (whole day Feb 9) = 89021. IRAT failure due to physical channel failure = 2569 (2.88% of total attempts).

Total IRAT attempts (whole day Feb 16)= 86247. IRAT failure due to physical channel failure= 2197 (2.54% of total attempts).

IRAT Failure rate during the NBH, BBH hour only will be higher than daily total.

Majority of these failures are due to cause “Physical channel failure”.

IRAT Failure Causes for Delhi24-Feb-2011


Mumbai drive analysis example - 1

e2d (compressed mode) triggered at good RSCP and Ec/Io


Mumbai drive example analysis – 1 contd.

Failure reason = Physical Channel Failure

Call returned to3G after the failureAnd then successfullyHanded over to 2G In later stage.


Mumbai drive analysis example- Layer 3

IRAT Fail due to Physical channel fail. GSM cell levels were good. No congestion issues found on target GSM cell. As mentioned before, call handed over to another GSM cell in later stage of the call.


Analysis of a Cell (12972) with High IRAT failure

RNC1/BSC6900UCell:Label = W_MB_MMBAI_068_10@2, CellID =12972 with 21 IRATHO.AttOutCS (IRAT attempts) and 20 failures, all due to physical channel failure.

Congestion in target 2G cells checked - No congestion.

Checked for missing 2G neighbor cells – 24, 3G-2G neighbors defined and 10 2G-2G neighbors defined on co-located 2G cell. 1 neighbor from 2G/2G neighbor not defined but HO attempts % from existing 2G/2G cell relation is only 1.8%.

3G-2G BCCH/BSIC discrepancy: NO discrepancies found.


IRAT thresholds – Mumbai

Inference: Different threshold values are in Mumbai and Delhi RNCs. In Mumbai Ec/No targets are -15 dBm while in Delhi, same is set at -14 dBm.


IRAT HO analysis for Delhi Feb 16 (Daily Total Stats)

VS.IR

ATHO.A

ttOut

CS.Tr

igDLT

xp

VS.IR

ATHO.A

ttOut

CS.Tr

igEc

No

VS.IR

ATHO.A

ttOut

CS.Tr

igRsc

p

VS.IR

ATHO.A

ttOut

CS.Tr

igULT

xp0

100002000030000400005000060000700008000090000

IRATHO attempts due to RSCP is very high (80,588) as opposed to IRAT HO attempts due to Ec/No (5381)

Inference: More IRAT HO attempts triggered at RSCP values below -100 dBm but at good Ec/No values.

These counters are currently not showing any data in Mumbai.


Key Observations

Attempts in the range of ~ 6000 for BBH and NBH.

Some counters like VS.IRATHO.FailRelocPrepOutCS.Abort , IRATHO.FailRelocPrepOutCS.HigherTrafficLod, IRATHO.FailRelocPrepOutCS.HigherTrafficLodare missing in the Mumbai raw data but available for Delhi.

The counter that shows a higher percentage of failures is IRATHO.FailOutCS.PhyChFail .- Physical channel failure.

Very high percentage of IRAT triggers due to RSCP as opposed to Ec/No.

Checked individual cells with high failures and most of the attempts were triggered by RSCP and failures by physical channel.


Conclusion & Recommendation

Compressed mode is starting early w.r.t RSCP and needs to be further optimized (as mentioned below) w.r.t Ec/No.

Our objective is to start compressed mode attempts when quality is poor and to reduce when quality is good. This could give the UE sufficient time to initiate and complete IRAT procedure.

Current setting of InterRATCSThd2DEcNo= -15 in Mumbai. This could be trialed out as -12 in non core areas on a case by case basis. This will start the compressed mode early before reaching bad quality and decrease possible failures due to RF issues. InterRATCSThd2fEcNo could also be modified accordingly and set to -10.

Current setting of InterRATCSThd2DRSCP =-100. This should be set to -104 to minimize compressed mode attempts which are still of good quality. InterRATCSThd2fRSCP should be set to -101.

irat analysis (2)

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