Analysis of a fountain codes based transport in an 802.11 WLAN cell

A fountain codes based transport (FCT) protocol relies on an alternate paradigm to that of the ubiquitous TCP. It abolishes the need for a reverse feedback mechanism usually essential to provide reliability in packet data transmission. Absence of a reverse feedback mechanism can substantially improve the performance of networks with half-duplex wireless channels (such as 802.11 WLANs), where collisions between forward and reverse MAC frame transmissions contribute significantly towards performance degradation. We propose a Markovian stochastic framework to model the performance of a simple FCT protocol in a single cell IEEE 802.11 WLAN. Our model allows the WLAN access point to employ a generic rate control algorithm for MAC frame transmissions on the downlink. Using renewal theory we provide an explicit expression for the average downlink throughput. ns2 simulations are used to validate our model and the analytically obtained throughput metric. A detailed performance analysis study is then carried out to provide insights into the choice of various system parameters that can lead to optimal throughput performance. Finally we present a brief comparison between the performance of FCT and TCP through simulations.