call drop

[simmus0300]

Hello all of u,
Pl tell me what are the possible reasons of call drop found during drive test using tems tool. Tell me about RX level,Rx Qual, C/I,SQI
Thanks.

[raedsab]

As a quick answer, below are the cases for drop calls in GSM:

Poor coverage
Channel interference
Missing neighbor
Incorrect external neighbor
Improper hardware calibration
Hardware fault
UL/DL interference
BSIC of dominant server can’t be decoded
Dominant server has blocking or cell-bar
External interference at UL, like wideband repeator
Faulty ancillary. UL path loss >>> DL path loss

[ThePyramid]

As a quick answer, below are the cases for drop calls in GSM:

Poor coverage
Channel interference
Missing neighbor
Incorrect external neighbor
Improper hardware calibration
Hardware fault
UL/DL interference
BSIC of dominant server can’t be decoded
Dominant server has blocking or cell-bar
External interference at UL, like wideband repeator
Faulty ancillary. UL path loss >>> DL path loss

Thanks ,man.

[raedsab]

Yet more drive test Analysis

http://rapidshare.com/files/19191709...t_Analysis.rar

[crisnspro]

especially now the GSM equiment is very cheap

[hassen]

As a quick answer, below are the cases for drop calls in GSM:

Poor coverage
Channel interference
Missing neighbor
Incorrect external neighbor
Improper hardware calibration
Hardware fault
UL/DL interference
BSIC of dominant server can’t be decoded
Dominant server has blocking or cell-bar
External interference at UL, like wideband repeator
Faulty ancillary. UL path loss >>> DL path loss

how it is possible cell bar cause drop call

[raedsab]

how it is possible cell bar cause drop call

As you know some cells are tested before taking them into commercial use by setting the CELL_BARRED (ON) in the base station,
thus normal GSM phones will not try to camp on these barred cells. Only test mobiles can camp on these cells.
But if you are in a low coverage area trying to handover to a better cell and the only best server has blocking or cell barring
than all calls and handovers requests to this cell will be blocked and the call may drop due to low coverage since there are no cells to handover to or due to blocking on the target cell .
This may be a rare case but it is worth mentioning.
Hope it is clear now!

[hassen]

As you know some cells are tested before taking them into commercial use by setting the CELL_BARRED (ON) in the base station,
thus normal GSM phones will not try to camp on these barred cells. Only test mobiles can camp on these cells.
But if you are in a low coverage area trying to handover to a better cell and the only best server has blocking or cell barring
than all calls and handovers requests to this cell will be blocked and the call may drop due to low coverage since there are no cells to handover to or due to blocking on the target cell .
This may be a rare case but it is worth mentioning.
Hope it is clear now!

cell bar access If enabled cell selection and reselection will be barred in idle
mode and there is no relation in active mode I mean Ms can make handover to this cell.

[raedsab]

Yes hassen, You are right Barred cells accept handovers from other cells, if incoming handovers are enabled in them.

More information about cell barring:
-Barred cell information is broadcast as system information to instruct MS’s not to camp on these cells

-Barring may be implemented when:
BTS is not functioning correctly
Cells are being tested
Cells reserved for handover purposes

-Barred cells accept handovers from other cells, if incoming handovers are enabled in them

-Barring a cell while carrying calls will not disconnect carried calls.
When a call finishes, reselection will be triggered

-Emergency calls (Class 10) are not and cannot be barred

[ullazusman]

I have experienced what raedsab is talking about during a DT. When I'm in a particular area of my route which as low coverage and my MS initiates a call setup. I get the message "call blocked due to barred cell." I haven't experience a handover in this area before though.

Thanks for the info Raedsab and Hassen.