Location management is crucial for mobile systems. A mobile must be located whenever a connection is established. Thus, mobile systems must cope with frequent location updates and queries. In addition to the HLR/VLR scheme in IS-41 and GSM, the feasibility of reducing the network load caused by locating mobile users has received considerable attention. One user location algorithm called "Pointer Forwarding with Single HLR," was proposed to reduce location update cost. Thereafter, the distributed HLR scheme was proposed to prevent HLR from becoming a signal bottleneck in the signaling network. This approach eliminates the cost of updating multiple HLRs, vastly reducing the database access delay, but also introduces long pointer chain traverse that may cause large location tracking costs and long call delivery times/costs. This study proposes a efficient location tracking strategy, named, "Fast Pointer Forwarding Strategy with Distributed HLR. " This strategy ensures that the pointer chain length never exceeds one. In fact, this strategy provides an upper bound on location tracking time. Its performance is numerically analyzed. Results in this study demonstrate that our strategy can considerably reduce the complexity of implementation and the call delivery time/cost.

In this paper, we propose a new location tracking method for pointer forwarding with distributed HLRs schemes to decrease the location tracking cost. Similar to the distributed HLR schemes, the location information is replicated on all HLRs in our scheme. However, unlike the traditional distributed HLR schemes, we propagate the most recent location changes from an HLR to reset the forwarding pointers in other HLRs, and thus reduce the cost of location tracking for call deliveries. The signaling cost of location propagation may be too costly to be practical. Therefore, we allow some inconsistency to exist among the location data of HLRs and defer the propagation of location changes to reduce the propagation cost. Three delay propagation policies are also proposed and analyzed using simulation. The performance result shows that the delay propagation policies reduce the propagation cost and the propagation resetting process degrades the location tracking cost. Our method preserves a low total cost for call deliveries, registrations and propagations in distributed HLRs.