Subject: Mobile Computing

Difficulty: Medium

Marks: 4 Marks

The Location Update process consists of the following phases Request for service; the MS detects that it has entered a new Location Area and requests to update its location.

The new MSC/VLR identifies the MS.

Authentication - The new MSC/VLR requests to the AUC for authentication parameters (SRES). Using these parameters the MS is authenticated.

Ciphering - Using the parameters which were made available earlier during the authentication the uplink and the downlink are ciphered.

Update HLR/VLR - The new MSC/VLR requests to update the MS location in the HLR. The MS is de-registered in the old VLR.

TMSI re-allocation - The MS is assigned a new TMSI.