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/191917096/Drive_Test_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.

[david_sam_1234]

it is realy very usefull data for us

dears , i wish if there is analysis reports for tested areas for 2G and 3G for you.

i will be very thankful

[ghassen]

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.

you have to see
cell barr qualify
tch drop rate
number of cleared request
tch assignement faillure
rxlev
rxqual

[hassen]

General Reasons for Drop Calls are as follows:

Drop Call due to Low Signal Strength
Drop Call due to Missing Neighbor
Drop Call due to Bad RX Quality
Drop Call due to Not–happening Handover
Drop Call due to Interference
Radio Failures
Radio Failures on old Channel in HO
Transcoder Failures.
Transcoder Failures of old Channel in HO
Abis Failures on old Channel in HO
Lapd Failures
BTS failures
Failures due to User Actions
Failures due to BCSU Reset
Failures due to Radio Network Configuration Action
Channel Activation Failures During Call

[simmus0300]

General Reasons for Drop Calls are as follows:

Drop Call due to Low Signal Strength
Drop Call due to Missing Neighbor
Drop Call due to Bad RX Quality
Drop Call due to Not–happening Handover
Drop Call due to Interference
Radio Failures
Radio Failures on old Channel in HO
Transcoder Failures.
Transcoder Failures of old Channel in HO
Abis Failures on old Channel in HO
Lapd Failures
BTS failures
Failures due to User Actions
Failures due to BCSU Reset
Failures due to Radio Network Configuration Action
Channel Activation Failures During Call


thanks for this.

[kiskhan]

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.


If you are talking about experiencing this situation in a 2G environment then, please check the neighbor list in the AUdit ****. I believe there you should find the cell which is barred and also the Incoming Handover paramater is disabled. Usually these parameters are located under the SM where you can change the settings.

[tibetan]

General Reasons for Drop Calls are as follows:

Drop Call due to Low Signal Strength
Drop Call due to Missing Neighbor
Drop Call due to Bad RX Quality
Drop Call due to Not–happening Handover
Drop Call due to Interference
Radio Failures
Radio Failures on old Channel in HO
Transcoder Failures.
Transcoder Failures of old Channel in HO
Abis Failures on old Channel in HO
Lapd Failures
BTS failures
Failures due to User Actions
Failures due to BCSU Reset
Failures due to Radio Network Configuration Action
Channel Activation Failures During Call


The question is how to determine root cause of a drop call.

[kiskhan]

The question is how to determine root cause of a drop call.

Well, then you need to look at the Layer 3 Messaging before and after of the drive test analysis. Actix or TEMS can pin point to the drop and specify the root cause (Radio Link Time out, Interference, etc...)

[John The Backfist]

The Layer 3 messges are useful but I find that this all has to be tied in back with statistics for the dropped calls and their reasons as the drive test information is limited to Downlink information.

[tibetan]

Well, then you need to look at the Layer 3 Messaging before and after of the drive test analysis. Actix or TEMS can pin point to the drop and specify the root cause (Radio Link Time out, Interference, etc...)

Neither Actix nor TEMS has the capability to quickly pin-point to the problem spots from a large number of drive test files. As for the root causes ... they are another hours away from even the experienced engineers... so don't place to much hopes for them to solve problems for you.

[hassen]

Well, then you need to look at the Layer 3 Messaging before and after of the drive test analysis. Actix or TEMS can pin point to the drop and specify the root cause (Radio Link Time out, Interference, etc...)
My friend don't forget drive test for downlink measurement and what about uplink (external interferance) for example.

[georgiadiy]

If it's possible, please, post list of 'dropcall reasons' for 3G networks

[alexfokin]

Maybe too much RWTP in UL. in other words too many ue's are serving in a cell and the RNC will start a disconnection of some calls

[alexfokin]

Maybe too much RWTP in UL. in other words too many ue's are serving in a cell and the RNC will start a disconnection of some calls

[nabil el haddani]

Hi guys,

Somebody know the parameter or the feature to disable incoming handover to the barred cell?

I'm using NSN.

Br,

Nabil

[aircom_vn]

General Reasons for Drop Calls are as follows:

Drop Call due to Low Signal Strength
Drop Call due to Missing Neighbor
Drop Call due to Bad RX Quality
Drop Call due to Not–happening Handover
Drop Call due to Interference
Radio Failures
Radio Failures on old Channel in HO
Transcoder Failures.
Transcoder Failures of old Channel in HO
Abis Failures on old Channel in HO
Lapd Failures
BTS failures
Failures due to User Actions
Failures due to BCSU Reset
Failures due to Radio Network Configuration Action
Channel Activation Failures During Call


thanks hassen, you r really VIP member. So professional !

[salmeterol]

Thanks, very useful