2G - High Call Drop Rate

[070057r]

Dear 2G Experts,

I have a cell that has higher call drop in signalling channel than in traffic channels. Can any please help me to improve the CDR?
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[justdream]

Are you sure you don't have transmission alarms

[070057r]

Yes . There are no alarms of any kind in the site. btw I'm in a Huawei network.

[fdanaei]

Hi dear friend, we need some info related to you issue:
1- How many TRX are there in the cell also how many available time slot?
2- Dual or single band cell?
3- Busy hour erlang of cell?
4- How many SDCCH? which TRX and TS have been used for sdcch channels definition?
5- sdcch erlang?
6- TRXs quality (1 to 7) in peak hour.
7- SDCCH handover is active or not?
8- Radio link time out parameter value of the cell?
9- Rxmin (Rx level access minimum) parameter value of the cell?
10- cell is lac border cell or not?
sorry but we need them for suitable answer.
Thank you

[hoangtuna]

I think this document may be helpful in this case

No pass required

[070057r]

Dear Fdanaei,

sorry friend I was little busy , couldn't answer your questions. Please help

1.4 TRXs 2.Dual 3.Around 10 Erlangs 4.6 , 4 in BCCH TRX and 2 in a TCH TRX 5.Around 10 Erlangs 6.How to get this? 7.No 8.32 9.-109 10.LAC Border and a BSC Border thanks

[baby2]

Dear Fdanaei,

sorry friend I was little busy , couldn't answer your questions. Please help

1.4 TRXs 2.Dual 3.Around 10 Erlangs 4.6 , 4 in BCCH TRX and 2 in a TCH TRX 5.Around 10 Erlangs 6.How to get this? 7.No 8.32 9.-109 10.LAC Border and a BSC Border thanks

number 6 , you can chk from counter RxQual

I think did you try to lock trx of BCCH CONFIG
and keep monitoring
some time,in Huawei trx problem w/o alarm

[070057r]

Dear baby2,

Can u please explain more.

[baby2]

Dear baby2,

Can u please explain more.

When you lock the trx that Bcch&sdcch&tch camp on ,the system will automatic assign Bcch&sdcch&tch to another trx

keep this lock and monitor kip for 1-2 day

[fdanaei]

Hi dear friend and sorry for late answer,
Related cell has following noticeable info:
TCH Erlang=10,
SDCCH Erlang=10,
LAC border Cell,
RxLevAccMin=-109dBm
It seems because location update, SDCCH traffic is high related to normal condition (because the cell is a boarder cell ).
Because RxLevAccMin=-109dBm, maybe, some of Location update requests are sent in very low signal level conditions that it causes SDCCH drop.
I think we must remove or decrease bad quality location update requests. For this, you can do the following actions:

1- check RxLevAccMin in neighbor cells, I think RxLevAccMin=-109dBm is very low. If this parameter be in the cell smaller than neighbors it causes that MS camp on this cell in low signal level areas. you can change it based on neighbors value. Rarely we set this parameter less than -105dBm in our network.

2- based on your info, the cell has 2 sdcch TS in BCCH TRX an one in nonBCCH, then the cell has 3*8=24 sdcch logical channel that is good for 10 erlang sdcch.
For trial and error, you can change nonBCCH defined SDCCH to another nonBCCH TRX. in some vendors you can not define sdcch TS more than 2 in BCCH TRX (because lapd overload) but if it possible put it in BCCH TRX.

3- Increasing hysteresis parameter in neighbor cells, decrease sdcch erlang and you can remove non bcch sdcch for test purpose.

4- you can think about Maximum Timing advance (MAXTA in huawei) parameter if location update requests are from long distance and you can not control overshooting by tilt and direction. It is last choice in this condition and we must be sure that when we reject a MS's requests by TA parameter, that MS can camp on better cell in that area.

I hope it can help you,

Dear Fdanaei,

sorry friend I was little busy , couldn't answer your questions. Please help

1.4 TRXs 2.Dual 3.Around 10 Erlangs 4.6 , 4 in BCCH TRX and 2 in a TCH TRX 5.Around 10 Erlangs 6.How to get this? 7.No 8.32 9.-109 10.LAC Border and a BSC Border thanks