Stabilization of contention-based CDMA ranging channel in wireless metropolitan area networks

TitleStabilization of contention-based CDMA ranging channel in wireless metropolitan area networks
Publication TypeJournal Article
Year of Publication2005
AuthorsWon, J. J., C. H. Cho, H. W. Lee, and V. C. M. Leung
Secondary AuthorsBoutaba, R., K. Almeroth, R. Puigjaner, S. Shen, and J. P. Black
JournalNetworking 2005: Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications Systems

The current IEEE 802.16a and 802.16d standards of wireless metropolitan area networks specify a ranging channel in the OFDMA physical layer that employs a set of CDMA codes for ranging and bandwidth requests. The ranging channel is contention-based and inherently unstable. In this paper, we propose two stabilization algorithms to enable efficient utilization of the ranging channel at close to the theoretical throughput limit, and analyze their performance using a continuous time Markov chain M/M/1 model. We show how to estimate system parameters such as the number of backlogged users, arrival rate and the first exit time for the critical. Based on these parameters, we present two methods for channel stabilization, for the cases that the number of ranging codes per frame is fixed and adjusted dynamically, respectively. We then present simulation results to show that, by restricting the actual arrival rate or dynamically adjusting the number of ranging codes, the ranging channel can be stabilized under all traffic conditions.

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