A mobility management strategy for GPRS

In General Packet Radio Service (GPRS), a mobile station (MS) is tracked at the cell level during packet transmission, and is tracked at the routing area (RA) level when no packet is delivered. A READY Timer (RT) mechanism was proposed in 3GPP 23.060 to determine when to switch from cell tracking to RA tracking. In this mechanism, a threshold interval is defined. If no packet is delivered within , the MS is tracked at the RA level. When a packet arrives, the MS is tracked at the cell level again. However, the RT mechanism has a major fallacy that the READY timers in both the MS and the SGSN may lose synchronization. This paper considers another mechanism called READY Counter (RC) to resolve this problem. In this approach, a threshold is used. Like the RT approach, the MS is tracked at the cell level during packet transmission. If no packets are delivered after the MS has made cell crossings, the MS is tracked at the RA level. We also devise an adaptive algorithm called dynamic RC (DRC). This algorithm dynamically adjusts the value to reduce the location update and paging costs. We propose analytic and simulation models to investigate RC, RT, and DRC. Our study indicates that RC may outperform RT. We also show that DRC nicely captures the traffic/mobility patterns, and always adjusts the threshold close to the optimal values.