2G problems :
a- Cross sector and cross feeder
There are 3 types of Cross sector
1-GSM cross sector
2-DCS cross sector
3-Total cross sector (GSM & DCS) cross sector
1-CROSS SECTOR
We must know the normal connection in first to understand the problems happened
Totally cross sector
in this case S1 is totally changed with S2
DCS cross sector
In this case DCS is changed between two sectors (S1,S2)
GSM cross sector:
GSM cross sector example
Cross sector between sec 1 & sec 3 on TEMS PRODUCT
GSM Cross feeder
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DCS cross feeder
DCS CROSS FEEDER EXAMPLE
GSM cross feederSector
Sector 2 & sector 3 appeared with equal levels beside sector 2
Hardware problem
The common HW problem is faulty DTRU
DTRU: Dual Transceiver Unit, Generate two frequencies
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To solve this problem you should replace this dtru with another one
BAD QUALITY
Rx qual is proportional to BER (Bit Error Rate), that affected by interference
Interference is appeared in hopping channel window (C/I)
C/I: Carrier to interference ratio.
Over shooting
It means that the cell serve at very long distance with good level This area that the cell overshoots in it most probably have cells with Co-channel or adjacent BCCH, so it will make interference that will result in bad quality
Reason:
Overshooting cell has small downtilt, 0 degree!
Overshooting cell has too high altitude
Closer cells have overshooting as well
BSIC of closer cells can’t be decoded
VSWR
Standing wave ratio (SWR) is the ratio of the amplitude of a partial standing wave at an antinode (maximum) to the amplitude at an adjacent node (minimum), in an electrical transmission line. The SWR is usually defined as a voltage ratio called the VSWR.
Missing Neighbors
This case may cause to dropped calls , bad coverage as the ms will not be able to HO on the target site as it’s not known for the serving site.
HAND OVER FAILURE
In the case of HO failure the MS fails to reach the target cell and so it returns
back to the source cell.
The reason for this case may be due to channel interference or poor coverage.
In the other case HO delay the BSIC of the neighbor is decoded but HO occurs
in much later time.
The reason for this case that all possible neighbors may suffer blocking or some
of the HO parameters (HO watch time , HO valid time) need to be adjusted.
Blocked call
The call may be blocked due to:
Cell congestion-
Bad quality due to interference.-
Faulty TRX.-
Bad coverage.-
Transmission problem.-
Long distance between MS and BTS (MAX TA = 63).-
Blocked call reasons.
No available TCH-
-No available SDCCH
-Bad Rxlev.
-Bad Quality
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DROPPED CALL
The call may be dropped due to:
- Bad quality due to interference.
- Faulty TRX.
- Bad coverage.
- Transmission problem.
reasons.
-Delayed HO àCongestion or wrong HO parameter definition.
-HO Failure.
-Bad Quality.
-Missing neighbor (Bad Rx level).
-Transmission problem (Not RF problem)
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