GSM Location Update Flow

The procedure of location update is as follows:

• When a MS finds that better service is provided in a certain location area, this MS notifies the MSC of the MSC/VLR which this new location area belongs to.
• If the original location area and new location area belong to the same MSC/VLR, the MSC only changes the location information of this MS in the VLR. If the original location area and new location area belong to different MSCs/VLRs, the new MSC/VLR requests the data of this MS from the HLR.
• The HLR returns the information needed by the new MSC/VLR and at the same time notifies the original MSC/VLR to delete the original registration information of this MS and notifies the new MSC/VLR to register this MS.

Location Update When the MS Roams Inside the Same VLR Area

Location Update When the MS Roams In the Areas of Different VLRs