Location Tracking with Distributed HLR’s and Pointer Forwarding

Location tracking operations in a personal communications services (PCS’s) network are expensive. A location tracking algorithm called pointer forwarding has been proposed to reduce the location update cost. The key observation behind forwarding is that if users change PCS registration areas (RA’s) frequently, but receive calls relatively infrequently, it should be possible to avoid registrations at the home-location register (HLR) database by simply setting up a forwarding pointer from the previous visitor-location register (VLR). Calls to a given user will first query the user’s HLR to determine the first VLR, which the user was registered at, and then follow a chain of forwarding pointers to the user’s current VLR. To reduce the “find” cost in call delivery, the PCS service provider may distribute HLR databases in the network. This paper integrates the concept of distributed HLR’s with pointer forwarding, and the new scheme is referred to as the pointer forwarding with distributed HLR (PFDHLR). Since no registration to the HLR is performed in the pointer forwarding scheme when a user moves to the new locations, the cost of updating multiple HLR’s is eliminated in PFDHLR. Our study indicates that PFDHLR may significantly reduce the mobility management cost compared with the single HLR approach.