Why UE/Mobile try to do routing area update while on ongoing voice call.

[Matulpagla]

In drive test UE was locked to 2G. UE is sending Routing Area Update request on NAS message while it was in dedicated mode voice call. Can anyone please answer why it is doing so?


Best regards

[laks777]

Network tracks location of UE based on LAU and RAU. Location area is for CS domain and RAU is for PS domain. Regardless of whether UE is in voice call, if it was registered to the PS domain through a GMM Attach, it should perform RAU when it moves from one RAU to another. Also RAU can be triggered through a periodic timer as well. Network can then page the UE in all the cells in that RAU, because in idle, network does not know the UE location at the cell level but only in the LA or RA level. Hope this helps.

[Matulpagla]

Thank you very much for the reply.

Can you please provide the timer name/number for LA & RA update? Is it possible to get this timer value from L3 messages?

Thanks

[laks777]

Its T3212 AND T3312. They are signalled in SysInfo messages, not sure which SysInfo exactly.
http://www.docstoc.com/docs/57214300/GSM-GPRS-Timers