Root Cause Analysis for downlink TBF drop rate degradation 2013-03-25

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Root Cause Analysis for xxxdow nlink TBF drop rate degradation

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Date

2010-07-02

HUAWEI TECHNOLOGIES CO., LTD.

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Root Cause Analysis for xxxdownlink TBF drop rate degradation

About This Document

About This Document Trouble Ticket Number

1632523

Prepared by

Baigang

Approved by Approval Date

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Contents

Contents About This Document......................................................................iii

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3 Problem Analysis

1 Basic Information Product Name

Version

BSC6900

V900R013ENGC00SPH556

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3 Problem Analysis

2 Problem Description Getting the feedback from Onsite engineer of Indonesia Telekom project, the TBF drop rate of two BSC named “BSCKE01”and “BSCSG02” had degradation after rehoming being executed. BSCKE01 did the operation in 2012-12-7 and BSCSG02 did the operation in 2013-1-23. The target value of the TBF drop rate is 2%. The problem needs to be solved as soon as possible. The statistical method of KPI: TBF drop rate of BSC in busy hour (20:00-22:00). The formula used is as follows: DL TBF Drop Rate= (A9106 + A9306) / (A9102 + A9302) UL TBF Drop Rate= (A9206 + A9006 + 9007+ A9207) / (A9002 + A9202)

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3 Problem Analysis

3 Problem Analysis 3.1 Aanlysis of BSCKE01 TBF drop rate Through analysis of BSCKE01 and BSCSG02’s performance data in busy hour (20:00-22:00) from Mar.1th to Mar.6th, we can see the uplink TBF drop rate has already reached the target value (2%). But the downlink TBF drop rate didn’t reach the target value and it is mainly resulted from the bad Downlink GPRS TBF drop rate. From the TBF drop rate formula we can see the downlink GPRS TBF abnormal release due to N3105 overflow.

Figure 1 BSCKE01 TBF drop rate

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3 Root Cause Analysis for xxxdownlink TBF drop rate degradation

Root Cause Analysis for xxxsuccessful rate of one cell tbf establishment

Figure 2 BSCSG02 TBF drop rate

3.2 Analysis of BSCKE01’s TOP cells After analysis of the busy hour (20:00-22:00) data, some TOP cells can be founded in BSCKE01. Such as TOP CELL 392、283 in BSCKE01. If get rid of the TOP cells , the Downlink TBF drop rate can reach the target value. From the analysis of TOP cell 392, we can see the Downlink GPRS TBF drop rate is bad in this cell.

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3.3 Analysis of radio environment 3.3.1 Analysis of BEP distribution From the BEP distribution from 17 to 31, we can see the BEP distribution from BEP 17 to BEP 31 is under 70%. So the radio environment is bad in TOP cell 392.

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Figure 3 BEP distribution(17~31) of cell 392

3.3.2 Aanlysis of electrical level and quality’s

distribution After analysis of electrical level and quality’s distribution in TOP cell 392, we can see the red frame in the nether figure ,the UL and DL quality are bad in the cell 392. So this means that the radio environment of the TOP cell needs to be optimized.

Figure 4 electrical level and quality’s distribution of cell 392

3.3.3 Aanlysis of retransmission After the analysis of BSCKE01’s TOP cell 392, we can see the Downlink GPRS TBF’s retransmission of cell 392 is bad. That means the radio enviroment is bad in the cell.

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Figure 4 Downlink GPRS TBF’s retransmission of cell 392

3.4 Analysis of UM signaling After analyzing the um signaling of TOP cell 392, we can see the radio environment is the main reason which cause the high retransmission and high TBF drop rate.

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Figure 5 um signaling of cell 392

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4 Root Cause There are some TOP cells in BSCKE01(CELLID 392 、283). The downlink TBF drop rate in these cells is bad and makes the KPI of the whole BSC can’t reach the target value. The radio environment especially the quality is bad in these cells.

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5 Next Plan 5.1 Next Plan 1、 Please push the spot engineer to optimize the radio environment of the TOP cells.

——Chong Mun Hou 2、 Provide the optimized parameter to optimize the KPI.

——Baigang

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6 Solution Optimize the radio environment of top cells in BSCKE01 (CELLID 392 、283)

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Root Cause Analysis for downlink TBF drop rate degradation 2013-03-25

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