Mumbai University > Computer Engineering > Sem 6 > Mobile Communication & Computing

Marks: 5 Marks

Year: May 2016

Home Location Register (HLR):

The HLR in telecom is the reference database for subscriber parameters. Actually HLR Having all the detail like customer ID, customer number, billing detail and for prepaid with IN intelligent network its has detail of current recharge of prepaid user.The HLR in telecom database contains the master database of all the subscribers to a GSM PLMN.

The Basic Parameters stored in the HLR in telecom are listed below:

1. Subscriber ID (IMSI and MSISDN)
2. Current Subscriber VLR (Current Location)
3. Supplementary Services Subscriber to (Caller Tone, Missed Call Alert, Any Other Services etc.)
4. Subscriber Status (Registered or Deregistered)
5. Authentication Key and AUC Functionality
6. Mobile Subscriber Roaming Number

Visitor Location Register (VLR):

The VLR contains a copy of most of the data stored at the HLR. It is, however, temporary data which exists for only as long as the subscriber is “active” in the particular area covered by the VLR.

The additional data stored in the VLR in telecom is listed below:

1. Location Area Identity (LAI).
2. Temporary Mobile Subscriber Identity (TMSI).
3. Mobile Station Roaming Number (MSRN).
4. Mobile status (busy/free/no answer etc.).

Location Area Identity in Both VLR and HLR in TELECOM

Cells within the Public Land Mobile Network (PLMN) are grouped together into geographical areas. Each area is assigned a Location Area Identity (LAI), a location area may typically contain 30 cells.

Each VLR controls several LAIs and as a subscriber moves from one LAI to another, the LAI is updated in the VLR. As the subscriber moves from one VLR to another, the VLR address is updated at the HLR.

Temporary Mobile Subscriber Identity (TMSI) is in VLR

The VLR controls the allocation of new Temporary Mobile Subscriber Identity (TMSI) numbers and notifies them to the HLR. The TMSI will be updated frequently, this makes it very difficult for the call to be traced and therefore provides a high degree of security for the subscriber.

Mobile Subscriber Roaming Number

As a subscriber may wish to operate outside its “home” system at some time, the VLR can also allocate a Mobile Station Roaming Number (MSRN). This number is assigned from a list of numbers held at the VLR (MSC). The MSRN is then used to route the call to the MSC which controls the base station in the MSs Current location.