Modeling and enhancement of the IEEE 802.11 RTS/CTS scheme in an error-prone channel

In this paper, we present a new discrete time Markov chain model to estimate the packet transmission probability tau, in order to develop mathematical models to derive the saturation throughput and the average packet delay of a 802.11 wireless LAN based on the RTS/CTS access method in the presence of noise, which distorts transmitted frames. Besides the standard backoff rule of the 802.11, Distributed Coordination Function assumes that each loss in the network is caused only by collision and acts to treat this situation by delaying the retransmission of the lost packet. We propose an enhancement of the IEEE 802.11 RTS/CTS scheme to recognize the reason of a transmission failure (collision or noise errors). Thus, the data packet is immediately retransmitted with zero-waiting time if a failure happens due to distortion by noise. This retransmission continues until the data packet is successfully transmitted or it is dropped when the number of packet transmission retries attains its limit. After that, we model the enhanced RTS/CTS scheme using a four-dimensional Markov model and we compare its performance with the actual RTS/CTS scheme.