sudden drop investigation report_revc.ppt

VIP AREASlide title In CAPITALS 50 pt Slide subtitle 32 pt
Investigation Report
Mobilis
Algeria
Top right corner for field-mark, customer or partner logotypes. See Best practice for example.
Slide title 40 pt Slide subtitle 24 pt Text 24 pt Bullets level 2-5 20 pt
EAL/O/EO Yasser SALEM
Problem Description
A slow increase of the drop call rate has been noticed on BSC level as well as cell levels.
BSC traffic trend was normal.
BSC congestion trend was normal.
BSC Handover success rate was normal.
BSC random access success rate was normal.
BSC TCH availability was fluctuating during the whole period of monitoring.
VIP AREA
Delly Ibrahim , El Achour and Babhessan area are inter MSC areas. A cell cet was defined on the BO in order to have an average value for the KPIs in this area.
Drop Call Rate Trend
Drop Call rate trend has a continues increase over a period of 6 consecutive weeks.
VIP AREA
Drop Call Reasons [BSC Level]
Drop call due to “Other and “Sudden loss” reasons were found to be the main reasons in the BSC level as well as cell level in the same period.
The worst 20 cells were not fixed during the whole period, but always the main reasons in the list were “Other” and “sudden loss”.
VIP AREA
Drop Call Rate [Cell Level]
About 15 cell of those having TCH drop > 2% have 100% drop Due to “Other”!!!!
Other 10 Cells of those having TCH drop > 2% have 100% drop Due to “Sudden Loss”!!!!
In accordance Hardware [RBS/TRM] was highly suspected and investigation procedure started by Field maintenance team, BUT a surprising Feed back was received saying “No errors at BTS side” !!!!.
A question has been Submitted to NT& C Technical focused community. The received suggestions and recommendations from Ericsson Expertise forms a deep investigation procedure.
VIP AREA
Slide title In CAPITALS 50 pt Slide subtitle 32 pt
Suspected Areas ?
Investigation Procedures?
Suspected Areas
4 Areas were defined and 4 investigation procedure has been performed
Radio Parameters
RLINKT,TX, MAXRET, …
VIP AREA
NON Radio:
Radio Investigation Team
Yasser Salem [Ericsson/NPOC]
Billel Cherouati [ATM/NPOC]
Radio Zone
Radio Parameters.
Drive test.
Radio Features.
Site16158 have 51% TCH drop Call rate with 100% drop due to “Other”
Site Sample
VIP AREA
Radio Zone [Radio Parameter]
A review and comparison of radio parameters have been performed between sample of cells having high drop call rate versus some cells did not have it especially for RLINKUP, RLINKT, MISSNM, TX, MAXTA, …
Review of Power parameter setting versus RBS type and CDU type in use.
Freq changes to avoid any possible External interference.
Parameter changes did not show any improvement !!!
Radio Parameters
Drive test
VIP AREA
Radio Zone [Drive Test]
Drive test was performed on a sample of Extreme sites [TCH Drop >30% and Drop Reason was 100% Sudden Loss or 100% other.
Drop reason was not clear in the drive test, But a repeated manner have been noticed in 40 test calls in same cell as following:
Call setup [Successful].
Call continue for 10 to 60 Sec.
intra cell handover to Half rate was noticed.
Long Beep, then drop!
VIP AREA
Radio Zone [Radio Features]
Based on the Drive test finding regarding the intra cell handover between Enhanced full rate and Half rate channels a decision was taken to perform the following test one after the other:
Stop EFR for a test period of three days. BUT No Improvement noticed !!!
CRT “change rate and type” property on the MSC level was set to DFRN, DHRN in order to prevent the change of channel rate during the Call. BUT Also No Improvement noticed !!!
Stop IHO for a test period of three days for a sample of affected sites. BUT No Improvement noticed !!!
Assignment to worse cell was OFF.
Immediate assignment on TCH was ON.
SDCCH Dim was max.
Radio Zone
RBS & TRM
VIP AREA
On site Hardware investigation Team
Elli Eid [Ericsson/FMO]
Billel Cherouati [Mobilis/NPOC]
Check alarm list [No Alarms on RBS from system side!!!]
ON site BTS Hardware investigation [TRU, CDU, DXU] [No Alarms on RBS, all the site was working normally !!!]
Antenna system Investigation [NO cross feeders, No broken feeders, No VSWR alarms, No lose connections, no earth protection problems, No major installation mistakes !!!!
HDSL modem Installation check [Mirnor Installation mistakes were found and corrected BUT no major changes in the site Performance !!!]
Site switch OFF/ON was performed BUT no major changes in the site Performance !!!]
DXU log file check. [DXU log shows a repeated error “Lost communication to transcoder” in accordance Transcoder to be investigated.
RBS & TRM
BSS Zone
VIP AREA
BSS Investigation team
BSS Zone [BSC side]
The following checks has been performed on sample of sites suffering from High drop call rate
Site definition on BSC. OK
Transcoder check. [Faulty Board was found then it was Blocked but no improvement was noticed!!!]
Transceiver handler check. OK
LAPD used check. [LAPD was changed from CONC/MULTX to Normal but no improvement was noticed !!!]
Dip Supervision has been performed [but it does not show common problem !!!].
DXU/TRU software version has been checked versus other sites in the same BSC and other BSCs. OK
BSS Zone
VIP AREA
Transport Network Investigation Team
Mohamed Habrout [Ericsson/NRO]
Transport network
E1s quality test [PCM analyzer test on site sample for 40 hours did not show transmission quality problem !!!!].
ML supervision [Minilink Quality supervision on sites for 60 min did not show quality problems !!!!]
DXX check. It was found that 98% of the sites suffering from TCH drop >2% have the same path [DXX-STM1].
A test procedure has been defined and prepared to be performed in the low traffic period.
Test-1: Near-end loop test [BSC to DXX]
Test-2: DXX check over [Routing, Cross connections, Synchronization, configuration,…]
Test-3 Far-end loop test [To include the STM1 supplied from the PTT as well as far end DXX].
VIP AREA
Transmission Area
OK
Test-3
TBD
Test-2
Test-1: Near end Loop test
No Errors or alarms at BSC side for a test period of 120 min. Pass
Test-2: DXX check over on going
DXX synchronization was taken from the STM1 itself, a decision was taken to change it to be taken from the BSC itself and monitor the effect for at least 24 hours.
Test-3: Far end loop test TBD
Test time to be defined based on Test-2 result.
Transport Network Test -2
MUS_DXX Synchronization was taken from the STM1 coming from AT.
It was changed to be taken from BSCMUS1 for small test period of 10Min between 13:30 to 13:40 on 11th of Sep.
This result as Synchronization reset.
Then after result of the near end loop test [TEST-1] which toke place at 12th of Sep midnight [00:00] a decision has been taken to fix the MUS_DXX Synchronization to be taken from BSCMUS1.
[TCH Drop Reasons]
TCH drop call due to Other has sharp decrease just after the Synch reset
at 11th of Sep 14:00.
[TCH Drop Rate ]
See how TCH drop call rate follow the same slope at 11th of Sep 14:00 !!!
Just after Synch-Reset
Drop Call Rate Trend BSCMUS1
The reduction of Drop call due to OTHER has direct impact on the overall drop call rate. This is show how strong the relation between the radio area and the Transmission area.
Radio performance is very much related to Field maintenance and Transmission performance.
Improvement in Transmission will improve most of the Radio KPIs not only the drop, such as Handover success rate.
VIP AREA
Handover Also has change at the same time
Incoming Handover performance
Incoming Handover Lost % has the same slop at the same time.
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Outgoing Handover performance
Outgoing Handover Lost % has the same slop at the same time.
VIP AREA
See how SDCCH and TCH Congestion affected
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Radio Performance
Eliminating NON radio causes [Transmission and RBS Hardware] give wider space to radio optimization for further improvement.
VIP AREA
Drop call tracing document.
Drop call Rate due to Other.
VIP areas follow up reports.
El-Biar
VIP Areas
Limited Internal
VIP AREA
El Biar area is one of the high traffic areas.
It has high building and relatively narrow streets which affecting the wave propagation.
Micro Street layer to be considered in such areas for better coverage and traffic capacity.
VIP AREA
Limited Internal
VIP AREA
El Biar is one of the VIP areas.
A Cell set was defined on the Business Object in order to have an average of the KPIs in this area.
18 sites were serving the whole area of El-Biar and its surroundings.
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Hardware stability
in
El-Biar
Limited Internal
VIP AREA
VIP AREA
Fluctuation of the TCH availability has bad impact on most of the KPI specially Drop, Congestion and Handover.
Limited Internal
VIP AREA
Normally Hardware problem is mutual responsibility between NOM/FO and FMO.
As Soon as NPOC are responsible for the performance they keep an eye on the Hardware stability and following up with FMO for fast repair actions.
Sample
TT:18374
16224
10-Sep-05
12-Sep-05
16224 is defined as S344 but working as S222, because there are no Enough TX capacity.
Transmission Capacity problem
TT:18195
16224
6-Sep-05
30-Aug-05
31-Aug-05
16226 is defined as S344 but working as S222, because there are no Enough TX capacity. 16109 1800 cells were fixed
Transmission Capacity problem, HW fault in 16109
TT:17359
16224
22-Aug-05
No Replay
Drop Call Rate
El Biar
Limited Internal
VIP AREA
<1%
Limited Internal
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Handover
in
El Biar
Limited Internal
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>97.5%
Limited Internal
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Limited Internal
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~2%
<0.5%
~98%
Eliminating NON radio causes [Transmission and/or Hardware] give wider space to radio optimization for further improvement.
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Limited Internal
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Outgoing Handover performance
TT:183741622410-Sep-05
S222, because there are no Enough TX
capacity.Transmission Capacity problem
capacity. 16109 1800 cells were fixed
Transmission Capacity problem,
Delly Brahim
VIP Areas
Limited Internal
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Delly Brahim [Delly Ibrahim, El Achour Bab Hessan]
Dark green sites represent the sites connected to MSCBMR1/BSCBMR1 and dark blue represent sites connected to MSCMUS1/BSCMUS1.
VIP AREA
Hardware stability
Delly Brahim
Limited Internal
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Fluctuation of the TCH availability has bad impact on most of the KPI specially Drop, Congestion and Handover.
Drop Call Rate
Delly Brahim
Limited Internal
VIP AREA
36.49%
Limited Internal
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Delly Brahim [SDCCH Drop Reasons]
Limited Internal
VIP AREA
SDCCH BQ
60.00%
Limited Internal
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SDCCH SS
63.20%
Limited Internal
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22.99%
Limited Internal
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30.05%
Limited Internal
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Delly Brahim [TCH Drop Reasons]
Limited Internal
VIP AREA
DLQ
63.20%
ULQ
48.94%
VIP AREA
Drop Calls due to Bad Quality in Up Link has been improved by 48%.
Drop Calls due to Bad Quality in Down Link has been improved by 63%.
Limited Internal
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ULSS
51.50%
VIP AREA
Drop Calls due to low signal strength in Up Link has been improved by 51%.
Limited Internal
VIP AREA
Other
35.71%
Sudden
7.30%
Drop Call Rate in
Delly Brahim
Radio causes for the drops have been reduced by Neighbor relation optimization , Frequency tuning, Power parameter adjustment as well as locating parameter tuning; which in turn have to reduce the total drops. BUT NON-Radio causes was strong enough to compensate that reduction and increase the overall drop call rate.
VIP AREA
NON Radio:
Handover
in
Delly Brahim
Limited Internal
VIP AREA
1 %
Limited Internal
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VIP AREA
More over the 1% improvement in the Incoming Handover success rate, the Handover reversion was improved by 33% which reflect the reduction of the Handovers to wrong candidates and this will reduce the BSC-CP Load due to un-necessary Handover processes.
Limited Internal
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VIP AREA
More over the 0.5% improvement in the Outgoing Handover success rate, the Handover reversion was improved by 14% which reflect the reduction of the Handovers to wrong candidates and this will reduce the BSC-CP Load due to un-necessary Handover processes.
Limited Internal
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SDCCH Drop due to Low Signal Strength
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SDCCH Drop Call Reasons
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12.00
14.00
16.00
18.00
20.00
22.00
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
08/01/05
08/02/05
08/03/05
08/04/05
08/05/05
08/06/05
08/07/05
08/08/05
08/09/05
08/10/05
08/11/05
08/12/05
08/13/05
08/14/05
08/15/05
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09/01/05
09/02/05
09/03/05
09/04/05
09/05/05
09/06/05
09/07/05
09/08/05
09/09/05
09/10/05
90.00
91.00
92.00
93.00
94.00
95.00
96.00
97.00
98.00
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
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DELLY_BRAHIM
DELLY_BRAHIM
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DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
DELLY_BRAHIM
08/01/05
08/02/05
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08/05/05
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09/01/05
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09/05/05
09/06/05
09/07/05
09/08/05
09/09/05
09/10/05
Outgoining Handover Trend
Causes unknown.
High TCH dropped calls due to other reasons
Caused by a loose connection to the antenna & resolved by tightening the connector
High TCH dropped calls due to other reasons
Funtion change in regional processor (RP) handling the RHDEV.
!Fetch RHDEV value on problematic TG
RXMDP:MO=RXOTRX-tg-trx;
BSC/TRC - R7.1
No alarms.
[email protected]
Caused by missing time slot definition in the mini-DXC after a TRU upgrade and resolved by defining the correct number of transmission time slots.
This was partly identified by performing TCH tests and comparing the BSC & mini-DXC mapping of time slots.
Notes:
1.
Uppgjord (även faktaansvarig om annan) - Prepared (also subject responsible if other)
Dokansv/Godk - Doc respons/Approved
OPEN
BSC Corrections [Half Rate]
Hi, I really suggest that you ask for support to review that all the updated packages have been loaded in the BSC's. We have seen these problems when we turn on some features like MAR-HR and the problem was that the BSC has not all the updated corrections and packages loaded. BR Alejandro
Anderson Falci (CE/EBS
Transcoders, Transmission, Transceiver Handler
Hi Yasser, it is very strange that scenario you describe in your message. I'm not sure of how many calls per cell per hour you are talking about but, anyway, I am sure you have a HW problem. First of all, try to identify the common resources the cells are sharing like transmission paths, transcoders, etc, mainly for cells with 100% of TCH drop due to other reasons. Try to see when this behaviour has started and search for hardware alarms that showed up in that date/time. Look at the transceiver handlers (RHDEV) those cells are connected to, try to identify if they are connected to the same RP. Synch problems are very common to generate that kind of problem, try to see alarms related to it. Verify if there have been changes on transmission paths, A-ter interface, transcoder pool configuration, synch sources, etc. I'm not sure the amount of historical statistic data you have, but it is the best proof that there is something besides RF that started in a specific date and degraded the system performance. And you mention a large group of cells that probably have no RF characteristics in common. Good luck and I'm available if you need more details. BR, Anderson.
Tony Delaney (DL/LMI)
BSC DIP Superv, Transcoders, Trancever Handler
Hi Yasser, Make sure you have DIP supervision active for all DIPs (DTQSP/DTQUP). Are these generating any alarms? DTQUP will show slips and errors. You need to check DIPs to BTS and TRC and/or MSC. Check your transcoders on this BSC and setup transcoder supervision if it is not setup already. Have the worst 15 sites any hardware in common i.e. RHDEVs on the same RP? Lastly, clear everything off the alarm list in the BSC. regards, tony
Claude Dhlomo (ZA/ESA)
RBS
Hi Yasser, Just turn the RBS off and on again, it should work.... BR///Claude.
Cesar Romero (E2/EEM)
Transmission [Synch]
Yasser: Just an idea: check the synchronization reference signal for all these BSCs / BTSs, specially if the transmission is not owned by the operator, but instead leased to a third party. AXE has good synchornization supervision tools (NSDAP for example. Have a look to cpistore for details) Regards. /César.
Johan Tägt (KI/EAB)
Transcoders, TRA/PCU
Hi Yasser, you can try to get an alarm and/or malfunction log and see if the transcoders are doing ok. I was working in a network where we detected a correlation between "other" and "TRA / PCU (Remote Transcoder / PCU Communication Lost)" When transcoder were checked they were blocked as of HW failure. Best Regards, Johan
Brs//
Weidong
weidong
TRA
Hi, would you pls. check the TRA pool in BSC node? First to check the alarm infor about TRA, if the state of TRA is Ok pls try to block and deblock the TRA device one by one. Only personal experience, FYI. Brs// weidong
Dr. A. Oguzhan KOCA
BSC[LAPD], RBS[TRU]
Please follow these procedures in order of priority printed... ie procedure 1 first and so on..... PRCEDURE-1 Symptom Symptom LAPD protocol errors 14,12,1 in TRU logfile Cause Cause There is a broken connection between DXU and TRU via x-bus or there's a loose contact of the pins connectors in the x-bus connector. Fix Fix Solution: Conditions: Procedure: 1. Check TRU pin connectors on x-bus. 2. Check pin connectors back plane cabinet if connectors not bend. 3. Insert properly the TRU to the TRU Magazine. 4. If same problem exist try to move the TRU to the other slots, if problem will follow the, TRU have a problem 5. If TRU has a problem 6. Replace TRU. 7 If said problem will raise only specific slot on the TRU magazine. 8. Replace TRU magazine. End Procedure PROCEDURE-2 Symptom Symptom LAPD protocol error 12 Symptom Symptom LAPD protocol error 1 Symptom Symptom There is a CF link disturbance (intermittent) Symptom Symptom BTS site will experienced outages Symptom Symptom PCM_UPDATE_RPT arived, error on 1st bit=1(standalone topology) Symptom Symptom PCM_UPDATE_RPT arived, error on 3rd bit=1(cascaded topology) Cause Cause CF link is broken on both direction (uplink and downlink) due to loose connection of PCM connectors. The said connector C7&C8 on plate C were located at connection field of the BTS & G703-1 on DXU. Fix Fix Mount properly C7,C8 connector on plate C and G703-1 on DXU. Tightened the mounting screw on the connector C7,C8 and G703-1. Note Note Before you fix or mount properly the connector into the mounting base connector, please see to it that the pins of the said connectors will not be misalinged or bend. PROCEDURE-3 Symptom Symptom Alarms: LAPD protocol errors 14, 12, 1 in DXU logfile Cause Cause LAPD errors 12 and 1 occurs when the link is broken in the downlink only or in both directions. LAPD Error 14 usually occurs when the link is broken in the uplink. Communication errors can have many causes like problems on the Local Bus or link problems to the BSC. Fix Fix
Rahul S. Sathe (BG/EIL)
Transmission [Synch] T200 Timer BSC[RBLT]
Hi Yasser, lot of things can cause these drops. here are few tips that may be helpful to you 1. Check Transcoders for bad faulty / inactive devices. 2. Check utilisation or congestion on E1s (both traffic and signalling) going to "other networks". 3. Check if you get timer T200 expired during call establishment / Handover procedure this is caused by RBLT LAPD link issues. 4. Check for stats on RBLT devices for errors on transmission
Weidong Li (HA/HEC)
BSC[TRU Pool]
Hi, Do you check the TRU pool in BSC node? And you can check the high drop call cell is controled by the TRU device, is it same TRU device? If it is sure, maybe it is the TRU device problem. you can block the related TRU device if the TRU is enough. Brs// weidong
Enrique Alvelo
Radio [Environment type] Transmission [Quality] Transmission [Synchronization]
Hello Yasser, Sudden Loss drops might happen when you have mobiles going quickly into closed spaces like elevators and tunnels or other hard to cover spots with no best server/high interference levels. Try verifying if any of these scenarios are present within the areas covered by these specific cells... Other causes might be faulty Tx links, Tx synchronization problems and timing problems within the RBS... Also, these kind of drops might happen when the battery of the mobile dies or gets disconnected. This is a little bit tricky to find out... Regards, Enrique Alvelo
Fabio Paulo
Radio [Parameters],Radio [Drive Test]

Area-2 Area-3
TCH Drop Reason, Other
BSC Drop Reasons Tracker
-1.00
0.00
1.00
2.00
3.00
4.00
5.00
6.00
93.00
94.00
95.00
96.00
97.00
98.00
99.00
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
0.00
200.00
400.00
600.00
800.00
1000.00
1200.00
1400.00
1600.00
1800.00
0.00
2.00
4.00
6.00
8.00
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
BSCMUS1
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BSCMUS1
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BSCMUS1
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09:00
11:00
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21:00
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01:00
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07:00
09:00
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09:00

sudden drop investigation report_revc.ppt

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