IRAT problem

[islam wagih]

Dear EXPERTS,

I'm so sorry for disturbance, just I have question. I have IRAT problem from 3G to 2G in E// site, when I checked configuration I found that it is due to LAC problem. site is in BSC 21 with LAC=602-02-5712-9173 but all other sites in BSC 21 with LAC=602-02-5212-XXXX . The site is defined on MSCS with LAC=602-02-5712-9173 and site working normally without any problems EXCEPT that there are n't any IRAT attempts to the site.

Just i didn't understand why this LAC problem affect only on IRAT without any other effect "DCLR/CFR" on the site.

and why IRAT is affected while LAC in BSC is the same in MSC "however it is not the right LAC" ?

[islam wagih]

Also what Commands should I use in BSC & RNC to check neighbor definitions ?

[Ghost78]

Hi;

check the lac configuration from RNC side, if the lac differs, you will get absolutely this IRAT issue, use the below command from the RNC where this 2G cell is defined as external gsm relation.

get ExternalGsmCell=xxxx lac

B.R

[Muhammad]

Hi;

check the lac configuration from RNC side, if the lac differs, you will get absolutely this IRAT issue, use the below command from the RNC where this 2G cell is defined as external gsm relation.

get ExternalGsmCell=xxxx lac

B.R


Actually this sort of issue is faced when your External cell definitions at 3G end are not consistent with 2G side. Either the mismatch in Cell ID, LAC / BSC ID may lead to IRAT HO failures. If this step is OK, if you have no External LAC definitions in MSC than this issue can also be faced. Check the Signaling traces at RNC and try to isolate the cause ID. it will help you in fault diagnosis.


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[islam wagih]

thank you for your reply, but but I revise all configuration from two sides BSC & RNC and all is OK LAC,BCCH,BSIC. also what do you mean with " External LAC definitions in MSC" and how could I check it ? >>
note that I checked LAC definition in BSC and MSC pool and no mismatch between them.

[Muhammad]

External LAC definition are done at the core side if 2G and 3G MSC are different. In this case the wrong definition or no definition may lead to IRAT failures. Actually the MSC has no info to route HO request in these cases.

[islam wagih]

Dear Muhammed,
Kindly support with steps to check theses external LACs, your support is very appreciated.

[rogand.lomboka@gmail.com]

Actually this sort of issue is faced when your External cell definitions at 3G end are not consistent with 2G side. Either the mismatch in Cell ID, LAC / BSC ID may lead to IRAT HO failures. If this step is OK, if you have no External LAC definitions in MSC than this issue can also be faced. Check the Signaling traces at RNC and try to isolate the cause ID. it will help you in fault diagnosis.


Please add reputation, if you find this post helpful.
hello Check also the Ho 2G to 3G bidirectionnal.