An auxiliary user location strategy employing forwarding pointers to reduce network impacts of PCS

We propose an auxiliary strategy, called per-user forwarding, for locating users who move from place to place while using Personal Communications Services (PCS). The forwarding strategy augments the basic location strategy proposed in existing standards such as GSM and IS-41, with the objective of reducing network signalling and database loads in exchange for increased CPU processing and memory costs. The key observation behind forwarding is that if users change PCS registration areas 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 rst query the user's HLR to determine the rst VLR which the user was registered at, and then follow a chain of forwarding pointers to the user's current VLR. We use a reference PCS architecture and the notion of a user's call-to-mobility ratio (CMR) to quantify the costs and beneets of using forwarding and classes of users for whom it would be beneecial. We show that under a variety of assumptions forwarding is likely to yield signiicant net beneets in terms of reduced signalling network traac and database loads for certain classes of users. For instance, under certain cost assumptions, for users with CMR < 0:5 forwarding can result in 20-60% savings over the basic strategy. This beneet comes at the price of moderately increased call setup times for the infrequent occasions when these users do receive calls.