1178 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 2, NO. 6, NOVEMBER 2003 A Mobility Management Strategy for GPRS Yi-Bing Lin, Fellow, IEEE, and Shun-Ren Yang Abstract—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 in that the RTs in both the MS and the serving GPRS support node 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. Index Terms—General packet radio service (GPRS), mobile net- work, mobility management (MM), wireless data. NOMENCLATURE The probability that an ON-period is followed by an OFF-period in the same session. The total number of states for an -layer RA random walk. The number of boundary edges in an -layer RA. The expected total cost for location update and terminal paging during . The net cost in an idle period with threshold . The expected location update cost during . The expected terminal paging cost during . The density function for the distribution. The density function for the distribution. The Laplace Transform for the distribution. The RC threshold. The expected value for the distribution. Manuscript received September 11, 2001; revised May 24, 2002; accepted July 3, 2002. The editor coordinating the review of this paper and approving it for publication is Y. Fang. The work of Y.-B. Lin was supported in part by MOE Program of Excellence Research under Contract 92-E-FA04–4, FarEastone, the Lee and MTI Center for Networking Research, NCTU. The work of S.-R. Yang was supported by the MediaTek Fellowship. Y.-B. Lin was with the Department of Computer Science and Information Engineering, National Chiao Tung University, Hsinchu 30050, Taiwan, R.O.C. He is now with the Institute of Information Science, Academia Sinica, Taiwan, R.O.C. (e-mail: liny@csie.nctu.edu.tw). S.-R. Yang is with the Department of Computer Science and Information Engineering, National Chiao Tung University, Hsinchu 30050, Taiwan, R.O.C. (e-mail: sjyoun@csie.nctu.edu.tw). Digital Object Identifier 10.1109/TWC.2003.819034 The expected value for the distribution. The expected value for the OFF-periods distri- bution. The expected value for the intersession idle pe- riods distribution. The number of cell crossings during . The number of RA crossings occurring between the th cell crossing and the th cell crossing during . The number of location updates (cell updates plus RA updates) during . The probability that after cell movements, an MS crosses RA boundaries provided that the MS is initially in an arbitrary cell of an RA. The probability that after cell movements, an MS crosses RA boundaries provided that the MS is initially at a boundary cell of an RA. The number of cells in an -layer RA. The RT threshold. The cell residence time of an MS at cell . The time interval between the end of a packet transmission and the beginning of the next packet transmission. The cost for a cell/RA update. The cost for paging in a cell. The variance for the distribution. The probability that an MS will leave an RA at the th step provided that the MS is initially in an arbitrary cell of the RA. The probability that after an MS enters an RA, it moves out of the RA at the th step. I. INTRODUCTION G ENERAL PACKET radio service (GPRS) provides packet-switched data services for existing mobile telecommunication networks such as global system for mobile communications (GSM) and digital advanced mobile phone service [10]. GPRS core network has also evolved into 3G network (i.e., universal mobile telecommunications (UMTS) [11]). Most GSM-based mobile operators are deploying GPRS for wireless Internet services. The network architecture of GSM/GPRS is shown in Fig. 1. In this figure, the dashed lines represent signaling links, and the solid lines represent data and signaling links. The core network consists of two service domains: a circuit-switched (CS) service domain (i.e., PSTN/ISDN) and a packet-switched (PS) service domain (i.e., IP). GPRS is evolved from GSM by introducing two new core network nodes: serving GPRS support node (SGSN) and gateway GPRS support node. Existing GSM nodes including base station subsystem (BSS), visitor location register (VLR), 1536-1276/03$17.00 © 2003 IEEE