Ia Access Protocol for Wireless §*

In this paper, we analyze the throughput performance of a wireless media access protocol taking into account the effect of capture in the presence of Rayleigh fading. For efficient access on the uplink (mobile-to-base), the protocol makes use of the uplink channel status information which is conveyed to the mobile through a busy/idZe@g on the downlink (base-to-mobile link). The uplink is slotted such that each slot duration is equal to one ATM cell duration. Each message generated at the mobiles is assumed to consist of a multiple number of ATM cells. Analytical estimates of throughput are derived for capture under slow fading and i.i.d. fading conditions. Throughput estimates obtained through simulations at various Doppler bandwidths validate the analysis. Next generation wireless systems must support not only voice communications, but a range of multimedia services (including data, video, etc.) as well [ 11. Asynchronous transfer mode (ATM) is widely being regarded as the enabling technology to realize this goal [2], [3]. ATM relies on packet switching where messages, irrespective of the nature of the message source (i.e., voice, data or video), will be segmented into fixed size (53 byte) packets (called cells) and transported across the network. Design and performance analysis of efficeient media access protocols for transporting ATM cells over wireless networks remains an important issue. Media access protocols play a vital role in determining the network efficiency in terms of throughput and delay performance when multiple mobile users share a common wireless medium. Classical random access protocols, for which extensive analyses have been carried out, are random ALOHA, slotted ALOHA, and carrier sense multiple access [4]. In this paper, we propose and analyze the performance of a media access protocol applicable to next generation wireless messaging systems. The proposed protocol uses the uplink (mobile-to-base station link) channel status information, which is conveyed to the mobile through the down-link (base station-to mobile link) broadcast from the base station by periodically inserting a busylidle flag. In addition, the protocol uses a header packet for each message, and the access procedure is so designed that collisions (due to simultaneous transmissions from different mobiles) are possible only during the header packets transmission and not during the data packets transmission. This feature of the protocol improves the channel utilization efficiency. We analyze the throughput performance of this protocol in a fading environment taking into account the effect of capture. Mobile radio channels are severely …