Hi Everybody. Whenever a re-election of GSM to LTE or WCDMA to LTE occurs, has a TAU occurred?
The answer to your question is Yes.
After a re-selection (2G to 4G or 3G to 4G) occurs the TAU. Even after a CSFB (when LTE network does not support VoLTE and the mobile originate/terminate a call in 3G or 2G and then returns to LTE Network) TAU occurs. TAU is composed by:
- Tracking area update request
- Tracking area update accept
- Tracking area update complete