GSM RNP&RNO Cases
GSM RNP&RNO Cases
Table of Contents
Table of Contents Chapter 1 Assignment Problem...................................................................................................... 1 1.1 Title: Can not make a call even there is high Rx level on mobile phone .............................. 1 1.1.1 Phenomenon Description:.......................................................................................... 1 1.1.2 Cause Analysis:.......................................................................................................... 1 1.1.3 Handling Process: ...................................................................................................... 1 1.1.4 Suggestions and Summary: ....................................................................................... 1 Chapter 2 Call Drop Problem .......................................................................................................... 2 2.1 Title: Interference causes Call Drop ..................................................................................... 2 2.1.1 Phenomenon Description:.......................................................................................... 2 2.1.2 Alarm Information:...................................................................................................... 2 2.1.3 Cause Analysis:.......................................................................................................... 2 2.1.4 Handling Process: ...................................................................................................... 2 2.1.5 Suggestions and Summary: ....................................................................................... 2 2.2 Title: Call Drop Problem Due to A-interface Congestion ...................................................... 2 2.2.1 Phenomenon Description:.......................................................................................... 2 2.2.2 Alarm Information:...................................................................................................... 3 2.2.3 Cause Analysis:.......................................................................................................... 3 2.2.4 Handling Process: ...................................................................................................... 3 2.2.5 Suggestions and Summary: ....................................................................................... 3 2.3 Title: Incorrect frequency led to a cell with abnormal traffic statistics................................... 4 2.3.1 Phenomenon Description:.......................................................................................... 4 2.3.2 Alarm Information:...................................................................................................... 4 2.3.3 Cause Analysis:.......................................................................................................... 4 2.3.4 Handling Process: ...................................................................................................... 4 2.4 Title: External interference leads to drop call ....................................................................... 4 2.4.1 Phenomenon Description:.......................................................................................... 4 2.4.2 Alarm Information: ................................................................................................... 4 2.4.3 Cause Analysis:.......................................................................................................... 4 2.4.4 Handling Process ....................................................................................................... 5 2.4.5 Suggestions and Summary ........................................................................................ 5 Chapter 3 Congestion Problem....................................................................................................... 6 3.1 Title: High TCH congestion rate caused by reverse connection between antenna and feeder cable ........................................................................................................................................... 6 3.1.1 Phenomenon Description........................................................................................... 6 3.1.2 Alarm Information ....................................................................................................... 6 3.1.3 Cause Analysis........................................................................................................... 6 3.1.4 Handling Process ....................................................................................................... 6 3.2 Title: TCH seizure failure for the difference of BCC and TSC .............................................. 7 3.2.1 Phenomenon Description........................................................................................... 7 3.2.2 Alarm Information ....................................................................................................... 7 3.2.3 Cause Analysis........................................................................................................... 7 3.2.4 Handling Process ....................................................................................................... 7 3.3 Title:Target Cell Blocking Cause Outgoing Handover Failure for a New Site On-air Commission Test ........................................................................................................................ 7 3.3.1 Phenomenon Description........................................................................................... 7 3.3.2 Alarm Information ....................................................................................................... 7 3.3.3 Cause Analysis........................................................................................................... 8 3.3.4 Handling Process ....................................................................................................... 8 Chapter 4 Handover ......................................................................................................................... 9 4.1 Title: Co-BCCH and Co-BSIC caused wrong attempted incoming inter cell handover ........ 9
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GSM RNP&RNO Cases
Table of Contents
4.1.1 Phenomenon Description........................................................................................... 9 4.1.2 Alarm Information ....................................................................................................... 9 4.1.3 Cause Analysis........................................................................................................... 9 4.1.4 Handling Process ....................................................................................................... 9 4.2 Title: A interface identifier deferent cause BSC handover successful ratio was low.......... 10 4.2.1 Phenomenon Description......................................................................................... 10 4.2.2 Alarm Information ..................................................................................................... 10 4.2.3 Cause Analysis......................................................................................................... 10 4.2.4 Handling Process ..................................................................................................... 10 4.2.5 Suggestions and Summary ...................................................................................... 10 4.3 Title: Non-configuration of BA2 table causes no handover ................................................ 10 4.3.1 Phenomenon Description......................................................................................... 10 4.3.2 Alarm Information ..................................................................................................... 11 4.3.3 Cause Analysis......................................................................................................... 11 4.3.4 Handling Process ..................................................................................................... 11 4.3.5 Suggestions and Summary ...................................................................................... 11 Chapter 5 Data Configuration Problem ........................................................................................ 12 5.1 Title: zero outgoing interBSC handover success rate ........................................................ 12 5.1.1 Phenomenon Description......................................................................................... 12 5.1.2 Alarm Information ..................................................................................................... 12 5.1.3 Cause Analysis......................................................................................................... 12 5.1.4 Handling Process ..................................................................................................... 12 5.1.5 Suggestions and Summary ...................................................................................... 12 5.2 Title: Wrong CGI causes low outgoing inter BSC successs rate........................................ 13 5.2.1 Phenomenon Description......................................................................................... 13 5.2.2 Alarm Information ..................................................................................................... 13 5.2.3 Cause Analysis......................................................................................................... 13 5.2.4 Handling Process ..................................................................................................... 13 5.2.5 Suggestions and Summary ...................................................................................... 13 5.3 Title: Wrong parameter settings of IDLE SD Thrash leads to fake congestion .................. 13 5.3.1 Phenomenon Description......................................................................................... 13 5.3.2 Alarm Information ..................................................................................................... 14 5.3.3 Cause Analysis......................................................................................................... 14 5.3.4 Handling Process ..................................................................................................... 14
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GSM RNP&RNO Cases
Chapter 1 HAssignment ProblemH
Chapter 1 Assignment Problem 1.1 Title: Can not make a call even there is high Rx level on mobile phone 1.1.1 Phenomenon Description: There is high Rx level on mobile phone (idle state) but can not make a call.
1.1.2 Cause Analysis: During the investigation by using Sagem testing MS, we found that there are several cells covering the problem spot. Rx level ranges from -76dBm to -92dBm. All cells covered the place are 900 cells (all cells CRO = 0). We have found the cell with highest Rx level covering very far (TA is more than 63), even though other cells covering closer (due to higher propogation loss their signal is lower). The Rx level of the second strength cell is about -80dBm, and its TA is 16. Considered that Rx_access_min in the 900 netwok equals 5, for 1st cell, C1 = 105-76 = 29 = C2; for 2nd cell, C1 = 105-80 = 25 = C2. 1st cell C2>2nd cell C2, therefore, the cell which TA<63, couldn't be chosen even the Rx level is high (-80dBm), and call cannot be established from it.
1.1.3 Handling Process: To solve the problem, need adjust downtilt or output power of the far coverage cell, or implement extended cell technology.
1.1.4 Suggestions and Summary: If possible, make software simulation before new BTS installation, and estimate coverage of the BTS. In those situations when coverage is very far (Rx>-80, TA>63), we need adjust antanna's downtilt during installation.
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Chapter 2 HCall Drop ProblemH
GSM RNP&RNO Cases
Chapter 2 Call Drop Problem 2.1 Title: Interference causes Call Drop 2.1.1 Phenomenon Description: call drop in highway always occurs in only one direction of the road .
2.1.2 Alarm Information: No alarm information
2.1.3 Cause Analysis: After checking eliminating hardware, congestion , path balance and coverage as a source for the problem . Thus it was obviouse that the problem was due to interference .
2.1.4 Handling Process: We did a drive test in the area using tems software connected to two phones one in idle mode and the other in dedicated mode we tested the road in both way . And the Drop occured as suspected . After analysing the logfiles of the DT we found that we found there is unjustified handover due to quality to a cell not suppose to serve in that area and it cause the call drop. After checking the logfile of the mobile in the idle mode there was cell overshooting to the area of call Drop and causing Co-channel thus causing the call drop. This cell didn't apear in the dedicated mode phon logfile. After changing the frequency a second drive test confirms that the problem was solved.
2.1.5 Suggestions and Summary: Performing Drive test for some problems is Mandatory . And some problem can be better viewed in idle mode .
2.2 Title: Call Drop Problem Due to A-interface Congestion 2.2.1 Phenomenon Description: Total 41 calls were attempted form the Ashulia bazaar Site. 24 (58%) calls were blocked.
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GSM RNP&RNO Cases
Chapter 2 HCall Drop ProblemH
DT was performed in the coverage area of DCS Ashulia Bazar on 14th December, 2006 (between 6PM & 7PM). As uplink (from Terminal) and downlink (from DT) data was simultaneously examined, it was clear that, there was available free TCH when the calls were blocked. [Excerpt from customer complaint sent on 14th December, 2006].
2.2.2 Alarm Information: E1 remote alarm, Mains supply failure, Second extended I/O alarm, Second extended I/O alarm.
2.2.3 Cause Analysis: Huawei Team made a series of Drive test and signal tracing in the problem zone after getting complaint from the customer. The alarms means Low voltage and Rectifier fault alarm.This alarm happened many times.Also, High temperature alarm. Because of the faulty E1 there occured E1 remote alarms. But even after the alarms were recovered the call blocking problems were not solved. Though the good signal level and good call quality there is a notable amount of blocked call in the site. During the DT there were following message from the L3 information when we encountered such block calls. "No circuit/Channel available".
2.2.4 Handling Process: From the traffic statistics it seems there is a notable amount of CM SERVICE REJECTIONS DUE TO CONGESTION in the CM Service rejection causes. The Description of this statistic item is , if NSS cannot normally respond to a CM SERVICE REQUEST message due to the congestion after receiving.this message from MS MM layer, NSS will respond MS a CM SERVICE REJECT message in which the rejection cause is congestion. Another important statistics item is the Percentage of A-interface circuit (Busy) reached more than 90% in the site which is resulting in the failure of a call. The traffic volume (excluding very early assignment) is 96.06Erl in the peak hour, 87.08ERL in FR and 8.98 ERL in HR. In terms of statistics excluding synchronization channel and NO.7 channel, 100 channels are available. So the traffic per A inferface channel is 0.96 (96.06 divided by 100). This value is much bigger than the recommended 0.7Erl/channel. This shows there is serious congestion on the A interface thereby making it difficult to make calls especially during busy hour.
2.2.5 Suggestions and Summary: The most critical thing required is to expand the A interface. Currently we have notable rejections during busy hour because of A interface congestion, this number should be brought down to zero by adding more circuits.
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GSM RNP&RNO Cases
Chapter 2 HCall Drop ProblemH
2.3 Title: Incorrect frequency led to a cell with abnormal traffic statistics 2.3.1 Phenomenon Description: The customer RNP engineers reported that one cell was abnormal from the traffic statistics, adding that the call drop rate became high and handover rate became low.
2.3.2 Alarm Information: High call drop rate and low handover rate
2.3.3 Cause Analysis: The frequency of the cell with abnormal traffic statistics was incorrect, which led to interference among the cells. As a result, there was need for changing the frequency for this cell in question
2.3.4 Handling Process: 1. Checked and analyzed the traffic statistics of this site; 2. Went to the site and carried out dial test with the result of high call drop rate and low handover rate; 3. Made local loop of radio frequency of that cell with abnormal traffic statistics, with the result of 5.5% error; 4.Checked all the frequency of the site and neighbour sites with the result of finding out that this frequency was incorrect; 5. Changed the frequency of the TRX and the error was corrected and the traffic statistics became normal.
2.4 Title: External interference leads to drop call 2.4.1 Phenomenon Description: During the driver test, MS faces drop call when the receiving signal is below -75dBm. At the same area, MS can't make call any more
2.4.2 Alarm Information: No any alarm on OMC
2.4.3 Cause Analysis: 1. weak signal. 4
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GSM RNP&RNO Cases
Chapter 2 HCall Drop ProblemH
2. interference in Um interface(uplink and downlink). 3. TRX or CDU faulty. 4. unbalance between uplink and downlink. 5. radio parameters are unsuitable. 6. transmission problem.
2.4.4 Handling Process 1. checked all the alarms of hardware on OMC and found no alarms on the hardware. 2. checked the traffic statistics and found that the cause is balance between uplink and downlink. 3. analyzed the drive test data and didn't find any downlink interference. 4. checked the traffic statictics and found that the "Average num. of idle TCHs in Interf. band 5" and "Average num. of idle TCHs in Interf. band 4" have big numbers. it means there exists uplink interference. The conclusion is proved by MS measurement reports which have high bit error rate in Abis interface. 5. this situation just exist one area which covered by sector 3 of site A. sector 1 and 2 are normal. 6. changed and swapped the TRX and CDU, the problem still exists. 7. because sector 1 and 2 are normal, so transmission of Abis interface is ok. 8. swapped antenna between sector 1 and 3 and found the problem still exists in that area. 9. the frequency resource came from airforce, so this is considered as external interference and brought spectrum tool to test the external interference. A jam was found in one rooftop and produced the interference in one direction. switched off this equipment, and the problem was solved.
2.4.5 Suggestions and Summary External interference is normal case in some country. when we face problems, we shall analyze the problem step by step
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GSM RNP&RNO Cases
Chapter 3 HCongestion ProblemH
Chapter 3 Congestion Problem 3.1 Title: High TCH congestion rate caused by reverse connection between antenna and feeder cable 3.1.1 Phenomenon Description High TCH congestion rate with some BTSs after expansion
3.1.2 Alarm Information None
3.1.3 Cause Analysis The network needs expansion due to the capacity requirement, and two transmitting antennas must be employed along with BTSs's configurations increasing. It is found out from the analyzing of traffic statistics result after expansion, that the receiving level of downlink signal is much low. The problem should locate in the stand-alone transmitting channel because all the expanded TRX are connected with the antenna by a stand-alone transmitting feeder cable.
3.1.4 Handling Process Check the transmitting channel from TRX, HPA to Combiner, and no connection fault of hardware is found. 2. Both TRX and HPA are replaced, but no improvement. 3. When call tests are done near the BTS, but the obvious difference of receiving level after expansion is not found from that of before expansion. 4. Tracing the Abis interface signaling, there are many TCH occupied failures when TA=2. The transmitting channels are interchanged, the TCH congestion occurs in the old TRXs. So the problem must locate in the feeder cable connected the antenna and the expanded TRXs. 5. Checking the jumpers on the tower, the transmitting antennas are connected reversely with the jumpers. The main reason is that the antenna labels below the tower are not installed, so that feeder cables are not in order on the platform of antennas. The jumper of Cell 1 is connected with the antenna of Cell 2, and the jumper of Cell 2 is connected with the antenna of Cell 1. Meanwhile the coverage directions of BCCH and TCH TRXs is different, the TCH occupied failures are very often.
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GSM RNP&RNO Cases
Chapter 3 HCongestion ProblemH
3.2 Title: TCH seizure failure for the difference of BCC and TSC 3.2.1 Phenomenon Description In one place, RNP engineer find that one site''s TCH seizure failure rate is high, and the other KPI is ok
3.2.2 Alarm Information No
3.2.3 Cause Analysis BCC and TSC should be same, if it is not same, TCH seizure failure rate must be high
3.2.4 Handling Process 1,Check the statistics, find that immediately assignment failure rate and handover assignment failure rate are high, but other site is ok after network optimization. 2,Check the frequency planning, no same frequency or adjacent frequency interference. 3,Test the signal in the site, no abnormal interference, so the reason is not for interference. 4,For traffic, this site is not busy, no congestion, so the reason is not for configestion. 5,Check the tables which have been modified, HSN, frequency and so on, no problem. 6,Finally, check the TSC parameter, find that: the TSC is different from BCC, change these two parameter to be same, the problem is solved
3.3 Title:Target Cell Blocking Cause Outgoing Handover Failure for a New Site On-air Commission Test 3.3.1 Phenomenon Description In dual-band network, the 1800 system is Huawei equipment, another vender is S company. "Cell-A" visualize "outgoing handover successful rate" is very low when we do commission test after cutover. When we do drive test find that even the serving cell Rx-lev is as poor as -100dBm, the mobile still doesn't handover to the other better signal strength G900 adjacent "cell-B", we use the forcing handover function several times but only few times handover successful
3.3.2 Alarm Information None
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GSM RNP&RNO Cases
Chapter 3 HCongestion ProblemH
3.3.3 Cause Analysis 1.Because force handover can be successful, so we can make sure that there is no trouble about data for handover. 2.Trace the signaling, check the same connect serial number, it visualize that huawei BSC send "handover required" to MSC, but there is no signaling of "handover command" for this "handover required" from MSC. 3. Check the statistics, the target G900 "cell-B" block rate is very high
3.3.4 Handling Process Change the penalty time for handover failure from "10s" to "20s". The mobile can't attempt to handover into "cell-B" again within short time after handover failure, the mobile handover to another adjacent cell successful and the problem solved
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Chapter 4 Handover
GSM RNP&RNO Cases
Chapter 4 Handover 4.1 Title: Co-BCCH and Co-BSIC caused wrong attempted incoming inter cell handover 4.1.1 Phenomenon Description One day we found one cell (cell A) which was not on air but still had attempted incoming inter cell handovers and TCH seizures, but all of them were failed
4.1.2 Alarm Information No Alarm
4.1.3 Cause Analysis We checked there were many attempted incoming inter cell handovers, but no incoming inter cell handovers, no successful incoming inter cell handovers and no attempted outgoing inter cell handovers. All the incoming inter cell handovers were failed. The number of incoming inter cell handovers was always same as TCH seizures, so it showed that all the TCH seizures failure were caused by handover. From above exact phenomenon, the most probability was that some closed cells(for example cell B) had Co-BCCH and Co-BSIC with cell A. when other cell(cell C) intended to hand over to cell B and it wrongly handed over to cell A. Of course, the handover would fail because cell A was not on air.
4.1.4 Handling Process According to above analysis, we checked the problem as following steps: 1)Checked the BCCH and BSIC and found there was a cell B (2 Km away) Co-BCCH and Co-BSIC with cell A. A and B didn’t have neighbor relation. A was defined neighbor relation with other closed cells. Some other cells which had neighbor relation with A can receive B’s signal because B had overshooting problem. So those cells would consider the signal was come from A. So it would handover to A wrongly. 2)Changed the BSIC of A and down tilt the antenna of B. after finished this, we checked the performance of A, and there were no attempted incoming handovers and TCH seizures.
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GSM RNP&RNO Cases
Chapter 4 Handover
4.2 Title: A interface identifier deferent cause BSC handover successful ratio was low 4.2.1 Phenomenon Description In Iran ESFAHAN MTCE, Customer have one MSC and two BSC. One MSC and one BSC belong to HUAWEI, we found that HUAWEI BSC handover successful ration was low. But ERRICSON BSC handover successful ratio was normal
4.2.2 Alarm Information No Alarm
4.2.3 Cause Analysis Because our INTRA-BSC handover was normal, so I think our handover data is correct. We can found ERRICSON sites can send require to HUAWEI sites, so two side data was consistent. We checked the traffic statistic, we can found our aim cell CGI, So MSC data also was normal. At last we doubted that link have some problems.
4.2.4 Handling Process Checked traffic statistic and found HUAWEI sites handover successful ratio was low. But ERRICSON sites handover successful was normal. Checked BSC handover parameters, everything is ok. Traced A interface link, checked that cause value"protocol error between MSC-BSC ---1100000", so I checked BSC and MSC A interface identifier. I found MSC identifier is GSM_phase_2+ and HUAWEI BSC identifier is GSM_phase_2,ERRICSON BSC identifier is GSM_phase_2+. I changed HUAWEI BSC identifier to GSM_phase_2+, that problem solved
4.2.5 Suggestions and Summary We need to attention some practical problems, although in theory GSM_phase_2+ and GSM_phase_2 are compatible. But in fact we couldn't do that.
4.3 Title: Non-configuration of BA2 table causes no handover 4.3.1 Phenomenon Description In a recent GSM Project which involves 1 (2-module) BSC + 4 BTS312 (S222/222) + 5 BTS312 (S222/444) + 3 BTS312 (S22/22), during drive test in the area, it was noticed that in dedicated mode, there was cell reselection and no handover from one cell/site to another. 10
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GSM RNP&RNO Cases
Chapter 4 Handover
4.3.2 Alarm Information No Alarm
4.3.3 Cause Analysis From the "Serving + Neighbor window", the serving cell was displayed with no neighbors being displayed; Non-configuration of BA2 table suspected
4.3.4 Handling Process 1.Reported the problem to BSS Engineer at the BSC site who did the configuration to check the adjacent relationship if it is ok; and it was observed that there was no problem with the adjacent relationship; 2.Also checked was the BA2 table if configured or not in BSC and it was observed that the BA2 was not configured; 3.The BA2 table was then configured dynamically in the BSC Auto Data Configuration system by the BSS Engineer; 4.Implemented DT to ascertain the anomaly has being corrected. BA2 list, is used to inform the MS in the active mode to search the BCCH frequencies of adjacent cells. BA list is sent through system information 5, 5bis, and 5ter. During network optimization, all BCCH frequencies in the network can be put into the BA2 table so as to use the performance measuring function of the undefined adjacent cells in the traffic statistics console to find out the adjacent missing cells. MS must keep on measuring the BCCH signal levels of the serving cell as well as the neighbor cells. In order to know the cells adjacent to the current serving cell, neighbor cell description information will be broadcast periodically in the system information of each cell. This information lists the BCCHs of all the neighbor cells. MS must extract this information from the system information and use it as the basis of neighbor cell signal measurement.
4.3.5 Suggestions and Summary This problem was as a result of an oversight from the BSS Engineer on site. As result of this, all site installation/configuration must be carefully checked by BSS Engineers and ensure to be in order before any other optimization measure is taken to solve problems discovered on site.
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GSM RNP&RNO Cases
Chapter 5 HData Configuration ProblemH
Chapter 5 Data Configuration Problem 5.1 Title: zero outgoing interBSC handover success rate 5.1.1 Phenomenon Description From the traffic statisticas we a found a cell with high attempted outgoing inter BSC handover but with zero success. There was only on external BSC neighbor
5.1.2 Alarm Information No Alarm
5.1.3 Cause Analysis The main reasons causing the failure of handover between cells follow: 1) Unreasonable handover data configuration 2) Problem with equipment (individual TRX damaged) 3) Congestion 4) Interference 5) Clock problem 6) Coverage 7) uplink/downlink unbalance There was no interference or congestion or hardawre problem. We suspect there is a a data configuration problem. We checked the neighbor and found one external neighbor.This neigbor was not online as we discovered from the BTS maintenance. After checking the sites around , we found a cell with the same BCCH as the external neighbor in the same BSC of the cell having the problem. and serving in the same area and it was not defined as a neighbor. So the problem was due to CO BCCH between undefined neighbor and offline external neighbor
5.1.4 Handling Process After adding the missing neighbor the cell having the problem at hand and changing the BCCH of the neibor added the inter BSC handover returned to normal
5.1.5 Suggestions and Summary When you have a handover problem check the neigbor defintion and possible cells that can be defined as a neighbor . Check for CO-BCCH CO-BISC problem
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GSM RNP&RNO Cases
Chapter 5 HData Configuration ProblemH
5.2 Title: Wrong CGI causes low outgoing inter BSC successs rate 5.2.1 Phenomenon Description we found a problem of low outgoing inter BSC successs rate
5.2.2 Alarm Information No Alarm
5.2.3 Cause Analysis call drop maybe caused by: 1. Unreasonable Parameter Settings. 2. Coverage. 3. Interference. 4. Transmission Failure. 5 Unreasonable Parameter Settings. 6. Uplink/downlink Unbalance Caused by Antenna & Feeder System
5.2.4 Handling Process No alarms are found.No problem in interfernce was found. after further analysing we found that specfic cell in the BSC cause this problem, and the cell is on the bordaer of the BSC. after invetigating the External neighbors of this cell we found there neighbors having wrong CGI.
5.2.5 Suggestions and Summary correct the CGI the neighboring cell in the external neighbors relation table of the BSC
5.3 Title: Wrong parameter settings of IDLE SD Thrash leads to fake congestion 5.3.1 Phenomenon Description Recently in TMIB network of Bangladesh we found that after comissioning new BSC at CTG(CB37) Version (G3BSC32V300R002C12), TCH congestion is around 5% to 10% in all cell at evening time. After checking the traffic statistics it is found that at the evening time TCH is congested where as from Erl B table it Confidential Information of Huawei. No Spreading without Permission
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GSM RNP&RNO Cases
0
should not be congested. It should carry more traffic then congestion. After checking the SDCCH congestion, found that no SDCCH congestion seen
5.3.2 Alarm Information No Alarm
5.3.3 Cause Analysis At first we check the data configuration specially cell data that is set by customer when comission those sites and found that in Channel Management Console the parameter IDlE SD Thrashold is put 24. Then from BTS Maintanance console check the BT view channel state and found that at evening time more TCH is converted to SDCCH where as dedicated SDCCH in IDLE.IDLE SD Thrash: When the number of idle SDCCH channels is less than or equal to the \Idle SD Thrsh.\, the system will try to find available TCHs and convert them to SDCCH channels.As this parameter set to 24, that meansall the time there would be idle SD channel less than 24, and System will convert more TCH to SDCCH, Also Min Recovery time is long (600S), so TCH channel would become less and leads to overflow.So the reason may be wrong setting of IDLE SD thrash leads to more TCH is Convered to SDCCH and leads fake congestion. The default value of this parameter is 2.
5.3.4 Handling Process Tue, 4 Apr 2006 09:35:00 UTC OVS Local SE 85725jonysaha So the reason may be wrong setting of IDLE SD thrash leads to more. TCH is Convered to SDCCH and leads fake congestion. The default value of this parameter is 2.As for trail we change one site this parameter and check the KPI next day and found that for that site all cells congestion vanishes. Later change all site this parameter.
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