2G E******* Inter BSC HO problem.

[wsoong]

Hi,

Anyone know what could be the problem if we encounter all the cells in BSC A could not Handover to BSC B?

Is there any BSC setting required? FYI, BSC A is a new BSC.

We almost have 100% handover failure in all the cell in BSC A.

Looking forward your reply.. :)

[Osman Nayeem]

Hi,

In most of the cases i found it happens only due to wrong definition in either BSC or MSC end. Please go through the following steps and check whether things are defined correctly or not. Hope it will helps:


1. Check NCCPERM for the internal and external cells [command- RLSSP:CELL=cell;].

2. Check Idle and active BA List [command- RLMFP:CELL=cell;] whether it is defined correctly.

3. Check external cells are defined (BCCH & BSIC) correctly in both the BSC or not [command- RLDEP:CELL=cell;].

4. Check if the CGI is correctly defined in BSC and MSC [for BSC, command is, RLDEP:CELL=cell; for MSC, command is, MGCEP:CELL=cell;].

5. These two BSC's are in the same MSC or not? if not, then please check external cells CGI is defined correctly in MSC or not [Command- MGOCP:CELL=cell;].


Thanks!

[wsoong]

Hi,

Pretty strange, as all the information seems correctly defined, except the parameter RO which is set to 0 compared to others cell.

Will this effect the HO? What does the RO parameter does?

1. Check NCCPERM for the internal and external cells [command- RLSSP:CELL=cell;].
Correct defined

2. Check Idle and active BA List [command- RLMFP:CELL=cell;] whether it is defined correctly.
Correctly defined

3. Check external cells are defined (BCCH & BSIC) correctly in both the BSC or not [command- RLDEP:CELL=cell;].
Correctly defined

4. Check if the CGI is correctly defined in BSC and MSC [for BSC, command is, RLDEP:CELL=cell; for MSC, command is, MGCEP:CELL=cell;].
CGI is correctly defined as well. However there is a different for a parameter RO.

CELL CGI BSC CO RO NCS EA

Found that BSC A, all the cells is set to RO=0 compare to the others cells which sits in the same switch.


5. These two BSC's are in the same MSC or not? if not, then please check external cells CGI is defined correctly in MSC or not [Command- MGOCP:CELL=cell;].
Both of the BSC belong to the same switch

[Osman Nayeem]

Hi,

I just checked and found RO means "Routing origin for mobile-originating calls". I think this RO could be routing path identity though not so sure about it. You can do one thing-- check the RO value of other BSCs belong to another MSC.

Last thing i can suggest- you can ask back office guys to check clock synchronization for BSC-A and BSC-B.

Please share if you can find out the root cause of this problem. The issue seems pretty interesting.

Thanks!

[takeiteasy612]

When i perform DT, when there is interBSC HO fail, the message will be "protocol, unspecified" right?

[wsoong]

Hi takeiteasy,

The handover failure i see, cause value is abnormal release, timer expired.

Hi Osman,

BSC A , has two inter BSC which is BSC B and BSC C. The strange thing is BSC A can Handover to BSC C but only having problem with BSC B.

And i found that the drive test log files, the cell in BSC A continously trying to handover to cell in BSC B eventhough itself is having good rx_level.

Synchronization, can we checking using the command handling? i tried nsstp; can you guide me?

[wsoong]

The problem due to one of the parameters in BSC were set wrongly. After changes it has handover back to normal according to the BSC personel.

[zeldalcl]

The problem due to one of the parameters in BSC were set wrongly. After changes it has handover back to normal according to the BSC personel. --> what is parameter? please, share your experience about this.

[wsoong]

Hi Friends,

The parameter changes was ALG.

Command:

rlcap;

There are 4 options for choosing the ciphering algorithm.

ALG1- Ciphering algorithm A5/1
ALG2- Ciphering algorithm A5/2
ALG3- Ciphering algorithm A5/3

NOCIPH - No ciphering.

The problem was due to this new BSC were set to ALG2 which is different ciphering algorithm to other BSCs.

The probrem resolved after change this using the same algorithm with the neighbor BSCs.

I learn something new through this problem. If you like my sharing please remember to give me some reputation. :p

Regards,
wsoong