Explain 2G problems faced telecom engineers in mobile field the
problems faced the telecom engineer in the mobile sites :
2G problems :
a- Cross sector and cross feeder
There are 3 types of Cross sector1-GSM cross sector2-DCS cross
sector3-Total cross sector (GSM & DCS) cross sector
1-CROSS SECTORWe must know the normal connection in first to
understand the problems happened
Totally cross sectorin this case S1 is totally changed with
S2
DCS cross sectorIn this case DCS is changed between two sectors
(S1,S2)
GSM cross sector:
GSM cross sector exampleCross 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 DTRUDTRU: 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 interferenceInterference is appeared in hopping channel window
(C/I)C/I: Carrier to interference ratio.
Over shootingIt 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 altitudeCloser cells have
overshooting as wellBSIC of closer cells cant be decoded
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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 NeighborsThis case may cause to dropped calls , bad
coverage as the ms will not be able to HO on the target site as its
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 returnsback 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 occursin
much later time.The reason for this case that all possible
neighbors may suffer blocking or someof 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 Congestion or wrong HO parameter
definition.-HO Failure.-Bad Quality.-Missing neighbor (Bad Rx
level).-Transmission problem (Not RF problem)
