A PREEMPTIVE POLLING PROTOCOL FOR APPLICATIONS IN WIRELESS LANS

This paper deals with a radio-based communication network with a singl e radio channel shared by several data terminals for transmissions to a single hub station. In particular, the communication system consider ed is a potential provider of wireless LAN-like services. The focus is on the capacity of combining a preemptive polling-based multiple acce ss scheme with a Selective Repeat ARQ technique to counteract the effe ct of the nonstationary transmission channel. The nonstationary transm ission channel has been modeled as a two-state Markov chain with param eters related to actual propagation conditions. Typical outdoor/indoor environments have been considered. The main idea is that of making th e service interruption of the preemptive polling scheme dependent on t he propagation conditions of the transmission channel by monitoring th e outcome of the data packet transmission attempts. A performance comp arison clearly reveals the superiority of this preemptive polling sche me with respect to the classical cyclic polling scheme.