03 G-LII 304 Case Study Of RNO-20080520-A-1.0
Transcript of 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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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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Case 6: Call Drop increased in THANH HOA city
Where is the interference?
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Case 6: Call Drop increased in THANH HOA city
-105/-108-105/-106-107/-108-102/-1048:30:0020070112THA_THA2_THANH-HOA-C
-106/-107-107/-108-109/-109-106/-1048:15:0020070112THA_THA2_THANH-HOA-C
-108/-108-109/-109-109/-108-103/-1048:00:0020070112THA_THA2_THANH-HOA-C
-108/-108-108/-107-109/-109-106/-1067:45:0020070112THA_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
-90/-95-89/-98-88/-101-89/-987:00:0020070112THA_THA2_THANH-HOA-C
-90/-95-89/-99-88/-102-89/-986:45:0020070112THA_THA2_THANH-HOA-C
-90/-95-89/-99-88/-102-89/-996:30:0020070112THA_THA2_THANH-HOA-C
Frequency87( mainset/sub set)
Frequency86( mainset/sub set)
Frequency85( 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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Case 6: Call Drop increased in THANH HOA city
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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Case 9: No half rate for whole BSC
Message Assignment Request Traced inHA TINH and THANH HOA BSC
Message Assignment Request Traced in NGHE AN BSC
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Case 9: No half rate for whole BSC
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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Case 10: Drive Test Log File Analysis 2
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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Case 10: Drive Test Log File Analysis 3
HO back to UL(900 band) of Cao-Lanh3_DTP
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Case 10: Drive Test Log File Analysis 4
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 )
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
V: TCH_MEAN_HOLDING_TIME (s)
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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Case 11: DTP Single Way Call
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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Case 11: DTP Single Way Call
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