03 g-lii 304 case study of rno-20080520-a-1.0

7/30/2019 03 G-LII 304 Case Study Of RNO-20080520-A-1.0

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HUAWEI TECHNOLOGIES CO., LTD.

TROUBLE SHOOTING & CASE STUDY---- GSM RNP & RNO 2008-02


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All Rights Reserved 2008, Huawei Technologies CO., LTD. Page 1

CONTENT

Foundational Trouble Shooting Method & Skill

Enhanced Case Study of GSM RNO


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Trouble Shooting Method Overview

Signaling AnalysisRemote Trace andAnalysisA, Abis, Um interface

Drive TestCheck on siteTest a point or a line in detail

OMC Traffic StatisticsRemote monitor andAnalysisNetwork, BSC, Cell level

NetworkTrouble


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Trouble Shooting Procedure

User complaintspecified (when, where,how)

It happen in cell levelor BSC level, in someplace or all

It happen in some houror whole day

It happen for some kindmobile phone, or somekind operator, or all

Whats thetrouble?

Check and fix hardwarealarm or connection problem

Parameter check and

optimizationFind interference sourceand get rid of it

Expand network capacityor upgrade for the softwareversion

How toresolve it?

Traffic statistics analysis,the problem caused by radiopart or BSS part. If caused by

BSS part any alarm, check if any operation done at the timepoint which problem occur

Signal tracing and analysis,find the detail reason

Drive Test and Call QualityTest

Why get thetrouble?

Su mmar i z e t he ex per i ence


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CONTENT

Foundational Trouble Shooting Method & Skill

Enhanced Case Study of GSM RNO


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Case 1: In VINH LINH site hard making call

Description: Subscriber complain that it is difficult to make call at QTVLH (Vinh Linh).

Procedure test: Drive test

Check on the hardware alarm, and hardware condition.

Check on antenna orientation, and antenna tilting.

Check on the RF parameter, found some parameter does not suitable.

Solution: Change of T3212 from 40 to 20. To standardize with MSC setting.

Follow up: drive test and follow up with the mobile phone dealer. No more complaint

received on the following days.


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Case 2: Coverage Issue in HA_TINH site

Case Description Customer complained the

signal was weak near the

HA TINH site

Analysis According to drive test

result, in Hopping channels,

we can see

The signal of 87, 89

frequency is 15dB better

than the other two

In HA_TINH_A sector we

cant handover to this cell

We suspect HA_TINH site

has swap feeder


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Traffic statistics Use the UL\DL

balance to checkthe swap feeder

problem

Summary for swap

feeder case

Swap between TCHTRX (TCH

assignment failure)

Swap between TCH

and BCCH TRX(one sector area no

main BCCH signal,

also TCH

assignment failure)

HA_TINH A and B Swap feeder before and after (above is before)

Swap between TCH TRX Swap between TCH and BCCH TRX

Case 2: Coverage Issue in HA_TINH site


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Case 3: Weak signal in one street of THANH HOA

GA_THANH_HOA TTA alarm cause the site coverage reduce

Before the alarm had been fixedBefore the alarm had been fixed

After the alarm had been fixedAfter the alarm had been fixed


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Case 4: Coverage issue in HA_TINH market

Subscribers in HA_TINH market complained signal is

weak inside the market.

NewBuilding HA_TINH

Market

Suggestion for this issue is adding new

site or add indoor coverage system for

market.


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Case 5: Bad Voice Quality issue in HA TINH BSC

Case Description Voice quality turned bad since March 19th in the city area of HA_TINH

Analysis Check the hardware equipment, no abnormal

Later receive the same kind of complaint from other area of HA TINH BSC,

so we suspect the E1 fault

Co-operated with VMS1 MSC engineer, we tested the transmission betweenTC and MSC one by one and found 3 E1 fault

Solution

Locked the fault E1 and changed to other transmission, and then voicequality became ok.


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Case 6: Call Drop increased in THANH HOA city

Case Description In THANH HOA city,

some cell suddenly got

the call drop timesincreased

Analysis

According to the trafficstatistics analysis, UL

interference is strong

in THANGH_HOA_C

cell, and a little strongin

GA_THANH_HOA_B

Chart 1: THANH_HOA_C turns bad at 7:00 am. Jan 5th

Chart 2: GA_THANH_HOA_B turns bad at 7:00 am. Jan 5th


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Where is the interference?


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-105/-108-105/-106-107/-108-102/-1048:30:0020070112THA_THA2_THANH-HOA-C




-102/-108-104/-108-105/-109-103/-1087:30:0020070112THA_THA2_THANH-HOA-C-90/-96-89/-100-88/-101-89/-987:15:0020070112THA_THA2_THANH-HOA-C




Frequency87( mainset/sub set)



Frequency

84 ( mainset/subset)

TimeDateObjects

THANH_HOA_C interference

disappeared at about 7:30am inJan 12 th

THANH_HOA_C interferencedisappeared at about 7:30am in

Jan 12 th


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After the

interference

disappear, this area

cells TCH call dropdecreased

GATHANH_HOA_B interference disappeared at about 7:30am in Jan12 th

THANH_HOA_3C interference disappeared at about 7:30am in Jan 12 th


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Case 7: KY_LOI Call Drop Case

67M:2, No: 4, Name: KY_LOI-22006-12-25 16:001314M:2, No: 4, Name: KY_LOI-22006-12-25 15:00

99M:2, No: 4, Name: KY_LOI-22006-12-25 14:00

1011M:2, No: 4, Name: KY_LOI-22006-12-25 13:00

22M:2, No: 4, Name: KY_LOI-22006-12-25 12:00

TCH seizure failures(internal clear)TCH call dropObjectsSampling Time

Case Description KY_LOI site is high in call drop, and the call drop type is not RF call drop

Analysis The mainly reason of Call Drops in KY_LOI site is internal clear. This reason means

that, there is some problem with the BSC hardware equipment, or the transmission

hardware equipment.


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Case 7: KY_LOI Call Drop Case

There are many

LAPD_OML alarms in

KY_LOI site

Suggestion is to

check and fix the

LAPD alarm of this

site


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Case 8: Immediate Assignment failure in THANH HOA

Abnormal signaling procedure is showed below, afterAssignment cant receive SABM frame. It will sendDEACTIVATE_SACCH when the Timer T3101 expired.

In THANH HOA province, some cells got many times Immediate Assignment Failure.Below is the normal signaling procedure for Immediate Assignment.


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Case 8: Immediate Assignment failure in THANH HOA

Solution Modify the

parameter

MAX_TA from 62

to 40, in order toforbid too far

access

Reason Only in THANH

HOA BSC has

this issue, we

suspect repeater

make the ghost

access.


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Case 9: No half rate for whole BSC

Case Description After swapping 1 Alcatel BSC to Huawei BSC, BSC has no half rate traffic.

Analysis Network topology: Before swap its Alcatel MSC-Alcatel BSC, After swap its AlcatelMSC-Huawei BSC. Signaling analysis: We traced the A interface signaling and found the Assignment

Request from MSC only permit this BSC FR speech version 1. So we judged this

problem was caused by wrong data configuration of BSC or MSC. Check BSC data configuration: Check cell data configuration in BSC, its correct.

Check circuit pool number, it was set to 7, which means this BSC can support FR speech

version 1,FR speech version 2,HR speech version 1. Check MSC data configuration: We check the Alcatel MSC data configuration, The

half rate parameter was set to DR (dual rate) nor DRMSV (dual rate and multiple

speech version), which means only permitted FR speech version 1.


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Message Assignment Request Traced inHA TINH and THANH HOA BSC

Message Assignment Request Traced in NGHE AN BSC


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Solution Change MSC half rate parameter from DR (dual rate) to DRMSV (dual rate and

multiple speech version), problem was solved.


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Case 10: Handover Frequently in Cao-Lanh

Issue Description: During Drive Test in Cao-Lanh site in Dec 12th, two places show handover frequently.

A: Weak coverage area,frequently ping-pong betweenTran-Quoc-Toan2_DTP andCao-Lanh1_DTP

B: Triangle handover : UL of

cell A -> OL of cell A -> UL ofNeighbor cell B -> UL of cell A->

Drive Test by VNP


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Case 10: Cao-Lanh Drive Test after Optimization

Result After doing optimization, Frequently Handover issue had been resolved, as showed

below:

Action1: Change Cao-Lanh1_DTP azimuth from 340-

>320 to improve Place Acoverage, its the main road

direction.

Action2: Increase PBGThandover threshold between 3sectors of Cao-Lanh site: from4->8, and increase PBGTwatch time and valid time: from

(4, 3) -> (5, 4) in order toreduce PBGT handover timesbetween different sectors of

Cao-Lanh.


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1) UL of cell A -> OL of cell A U to O HO Received Level Threshold : 35, if current signal > -75dBm, it will trigger U->O

HO, make OL get more traffic.

2) OL of cell A -> UL of Neighbor cell B PBGT HO Threshold : 68=4dB, if Path loss A Path loss B > 4dB, and during PBGT

watch time : 4s, last PBGT valid time : 3s. O to U HO Received Level Threshold : 20, it means if signal reduce to -90dBm will HO

from O -> U. So it trigger PBGT HO to neighbor cell, for 1800 coverage is always weakerthan 900 band.

3) UL of Neighbor cell B -> UL of cell A But actually, this area Neighbor Cell Bs 900, is not

as strong as Cell As 900. So it will HO back to

UL of Cell A.

If the MS stand at this area,

it may triangle handover

again and again

Case 10: What is Triangle Handover?

ULOL

Cell A

UL

OL Cell B

3

1

2


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Case 10: Drive Test Log File Analysis 1

Now MS is using OL(1800 band) of Cao-Lanh3_DTP. Preparing HO toUL(900 band) of Cao-Lanh2_DTP by PBGT HO.


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After HO to UL(900 band) of Cao-Lanh2_DTP, it find Cao-Lanh3_DTPis stronger than Cao-Lanh2_DTP, preparing HO back to UL of Cao-Lanh3_DTP.


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HO back to UL(900 band) of Cao-Lanh3_DTP


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HO back to OL(1800 band) of Cao-Lanh3_DTP


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In order to reduce Triangle Handover, we must reduce step 2.

Why? Step 1 is UL to OL, for Co-BCCH cells, UL is 900 for coverage, OL is 1800 for traffic load, so we

prefer MS to use OL sub cell channel if the 1800 quality is not so bad. We cant modify parameter to

avoid or delay the HO form UL to OL, otherwise OL channel will be wasted and UL will be easy tocongested.

Step 2 is PBGT from 1800 to neighbors 900, PBGT is triggered only between the same layer cells.

For dual band co-site, we often set 1800 cell layer higher than 900, but for Co-BCCH cell, 900 and1800 combined into only one cell, so OL of Cell A is the same layer with UL of Cell B, even they are

using different frequency band and 900 is much better than 1800(about 10 ~ 20dB stronger). In this case we must try to delay the PBGT handover from 1800 to neighbors 900, so we increase

PBGT handover threshold between 3 sectors of Cao-Lanh site: from 4->8, and increase PBGT watchtime and valid time: from (4, 3) -> (5, 4) to reduce PBGT handover times between different sectors of

Cao-Lanh.

Case 10: How to Anti Triangle Handover

ULOL

Cell A

UL

OL Cell B3

1

2


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Case 10: PBGT Handover of Cao-Lanh After Modify

PBGT Handover timesreduced afterparameter optimization,this means triangle

handover times alsoreduced accordingly.

Before

After


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Case 11: DTP Single Way Call

V: TCH_MEAN_HOLDING_TIME (s)

15

20

25

30

35

40

45

1 6

1 2

- 1 1

1 8

1 2

- 1 1

2 0

1 2

- 1 1

8 1

2 -

1 2

1 0

1 2

- 1 2

1 2

1 2

- 1 2

1 4

1 2

- 1 2

1 6

1 2

- 1 2

1 8

1 2

- 1 2

2 0

1 2

- 1 2

8 1

2 -

1 3

1 0

1 2

- 1 3

1 2

1 2

- 1 3

1 4

1 2

- 1 3

1 6

1 2

- 1 3

1 8

1 2

- 1 3

2 0

1 2

- 1 3

8 1

2 -

1 4

1 0

1 2

- 1 4

1 2

1 2

- 1 4

1 4

1 2

- 1 4

1 6

1 2

- 1 4

1 8

1 2

- 1 4

2 0

1 2

- 1 4

8 1

2 -

1 5

1 0

1 2

- 1 5

1 2

1 2

- 1 5

1 4

1 2

- 1 5

V: TCH_MEAN_HOLDING_TIME (s )


15

20

25

30

35

40

45

50

1 6

1 2

- 1 1

1 8

1 2

- 1 1

2 0

1 2

- 1 1

8 1

2 -

1 2

1 0

1 2

- 1 2

1 2

1 2

- 1 2

1 4

1 2

- 1 2

1 6

1 2

- 1 2

1 8

1 2

- 1 2

2 0

1 2

- 1 2

8 1

2 -

1 3

1 0

1 2

- 1 3

1 2

1 2

- 1 3

1 4

1 2

- 1 3

1 6

1 2

- 1 3

1 8

1 2

- 1 3

2 0

1 2

- 1 3

8 1

2 -

1 4

1 0

1 2

- 1 4

1 2

1 2

- 1 4

1 4

1 2

- 1 4

1 6

1 2

- 1 4

1 8

1 2

- 1 4

2 0

1 2

- 1 4

8 1

2 -

1 5

1 0

1 2

- 1 5

1 2

1 2

- 1 5

1 4

1 2

- 1 5

V: TCH_MEAN_HOLDING_TIME (s )V: TCH_MEAN_HOLDING_TIME (s)

15

20

25

30

35

40

45

1 6

1 2

- 1 1

1 8

1 2

- 1 1

2 0

1 2

- 1 1

8 1

2 -

1 2

1 0

1 2

- 1 2

1 2

1 2

- 1 2

1 4

1 2

- 1 2

1 6

1 2

- 1 2

1 8

1 2

- 1 2

2 0

1 2

- 1 2

8 1

2 -

1 3

1 0

1 2

- 1 3

1 2

1 2

- 1 3

1 4

1 2

- 1 3

1 6

1 2

- 1 3

1 8

1 2

- 1 3

2 0

1 2

- 1 3

8 1

2 -

1 4

1 0

1 2

- 1 4

1 2

1 2

- 1 4

1 4

1 2

- 1 4

1 6

1 2

- 1 4

1 8

1 2

- 1 4

2 0

1 2

- 1 4

8 1

2 -

1 5

1 0

1 2

- 1 5

1 2

1 2

- 1 5

1 4

1 2

- 1 5


Sa-Dec_DTP Mean Holding Time TrendProblem Description: User complained single waycall in Sa-Dec_DTP site.

Analysis: From CQT we found the percentage of

single way call was nearly 90%, so we suspect it

caused by equipment and transmission part. FromOMC Traffic Statistics, we can see this problem

began from 12-14 10pm. Because in single way

bad cells, subscriber will hung up more quickly, so

that MHT will be shorter, like the charts shows here.


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Result: After Switch the GTNU board in 13:00 12-16, Mobile A and B can hear each

other. And then did CQT, one way call did not happen anymore.

Double checked by OMC Traffic Statistics, this problem didnt exist.


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Some days later, single way call happen again. The percentage of single way call

was about 30%

Check traffic statistics, found some abnormal in A-interface from 01-21 10:00AM.

Confirmed with customer, the subscriber complaint also start from that time point.

At last, we asked OMC engineer, they expanded some A-interface at that time, and

the A-interface quality was not good. After locked these A-interface, the single way

call disappeared.

109.303102.283BSC_242H_DTP12:00:0021/01/2008

109102BSC_242H_DTP11:00:0021/01/2008

58.74490.089BSC_242H_DTP10:00:0021/01/2008078.217BSC_242H_DTP9:00:0021/01/2008

078BSC_242H_DTP8:00:0021/01/2008

078BSC_242H_DTP7:00:0021/01/2008

AL0089:Mean Number of

Circuits with UninstalledPeer Circuits on the AInterface

AL0050:Mean Number

of UninstalledCircuits on the AInterfaceBSC NameTimeDate


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Thank You

03 g-lii 304 case study of rno-20080520-a-1.0

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