drop call analysis
TRANSCRIPT
MOS report for VMS
Drop Call No. 1 & 2
1. Drop Call No.1 & Drop Call No.2:
Serving Cell: CI=10471, LAC=113, BSIC=75, BCCH=88;
Time: 17:43:29 pm;
Date: Oct 9th.
Description: Both the outgoing and incoming call mobiles dropped at the same time.
2. Problem analysis:
The mobile received RxLevBCCH=-83dbm (within normal range) from the serving cell (CI=10471,
LAC=113, BSIC=75, BCCH=88); but Rx_Quality_Sub=7, which means the speech quality was very poor.
There was more Measurement Reports than usual appeared at the uplink, which means the mobile received
strong interference signal from adjacent frequency and caused high BER. In such cases, the mobile might not
able to demodulate the BSIC of neighbor cells; the serving cell cannot receive Measurement Reports correctly.
The above problems would result in interferences to network during a call then eventually caused poor speech
quality and drop call.
3. Advised solution
a) First check the frequency allocation around the serving cell to see if there is inappropriate allocation that
causes interference to the same or adjacent frequency.
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MOS report for VMS
b) Check interference caused by equipments. For example, self-excitation of carrier frequency device,
intermodulation interference of antenna, performance degradation of antenna, repeater station etc.
c) Check traffic statistics from OMC. For example, cells that have frequent handover failure, performance
measurements of interference spectrum, receive level, receive quality and drop call.
d) If the interference is external to the network, use sweep generator to search the source of interference.
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MOS report for VMS
Drop Call No. 3
1. Drop Call No.3
Serving Cell: CI=10471, LAC=113, BSIC=75, BCCH=88;
Time: 17:46:30 pm;
Date: Oct 9th.
Description: The outgoing call mobile dropped.
2. Problem analysis:
The mobile received RxLevBCCH=-60dbm (within normal range) from the serving cell (CI=10471,
LAC=113, BSIC=75, BCCH=88); but Rx_Quality_Sub=7, which means the speech quality was very poor.
There was serious interference to the cell and caused drop call.
3. Advised solution
First to check the frequency allocation around the serving cell (CI=10471, LAC=113, BSIC=75, BCCH=88).
If there is any mistake in the allocation, amendment is needed to eliminate inter-network interference. If the
allocation is correct, check around this area for any repeater or jammer that may cause external interference.
Drop Call No.4 (Adjacent frequency interference)
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MOS report for VMS
1. Drop Call No.4
Serving Cell: CI=14281, LAC=142, BSIC=42, BCCH=97;
Time: 11:42:11 pm;
Date: Oct 12th.
Description: The outgoing call mobile dropped.
2. Problem analysis:
The mobile received RxLevBCCH=-75dbm (within normal range) from the serving cell (CI=10471,
LAC=113, BSIC=75, BCCH=88); but Rx_Quality_Sub=7, which means the speech quality was very poor. The
neighbor cell information demonstrates that there was serious adjacent frequency interference from neighbor
cell. The interference caused high BER and poor speech quality then drop call.
4. Advised solution
Adjacent frequency re-allocation is advised for base stations around the serving cell.
Drop call No.5, caused by across-boundary coverage:
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MOS report for VMS
3. Phenomenon
Log file name: LOG_2008-10-10_15-02-48-386.lg4
Time: 16:28:20 pm;
Date: Oct 10th.
Description: The outgoing call mobile dropped.
4. Problem analysis
The mobile switched to the serving cell: CI=10133, LAC=132, BSIC=27, BCCH=90 at 16:28:20 pm.
RxLevBCCH=-60dbm (within normal range). At the same time the mobile received strong signal
(RxLevBCCH=-56dbm, greater than the serving cell) from Cell=HNI_BDH3_PHO_DUC_CHINH,
BCCH=89, BSIC=55 and caused drop call (RxQualSub=7).
5. Advised solution
We advise to examine the neighbor cell information of the cell CI=10133, LAC=132, BSIC-27, BCCH=90.
We advise on declination of the antenna of Cell= HNI_BDH3_PHO_DUC_CHINH, BCCH=89, BSIC=55.
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