Cooperation in Random Access Networks: Protocol Design and Performance Analysis

This paper tries to answer the questions of how to enable cooperative communications in random access networks. And, since cooperation introduces extra transmissions in the channel, what are the benefits and possible tradeoffs associated with cooperation? To answer these questions, a novel cooperative protocol for wireless networks based on IEEE 802.11 random access protocol is proposed. Cooperation is achieved through the deployment of a relay node that intelligently access the wireless medium without imposing any penalties in terms of increased collision probability. To help other network nodes, relay stores packets in its queue, and accesses the channel after each transmission attempt made by any network node. Using this scheme, relay is guaranteed uncontested access to the channel. To capture the interactions between different network nodes and the relay, the network is modeled using Markov chains in conjunction with queuing analysis. Throughput and delay performances of the proposed protocol are characterized and compared to CSMA/CA without cooperation. The results demonstrate that significant gains are achieved by the proposed cooperative protocols.