GPRS Location Update Channel

Hi Experts,

I am really new to this GSM and GPRS side of things.

I was asked a question from my seniors at work, What channel is used for Location Update on both CS and PS mode.

I was able to find that for BCCH channel is used in CS mode.

I just wanted to confirm that PBCCH channel will be used for Location Updating in PS mode. Is it also used for Periodic updating or is it only used on cell changes.

Would you also be able to provide some kind evidence from 3GPP or any standard documents or book.

Thanks in Advance Experts