CARLA: Combining Cooperative Relaying and Link Adaptation for IEEE 802.11 Wireless Networks

In this paper, we present a novel design named CARLA which combines Cooperative Relaying and Link Adaptation for IEEE 802.11 wireless networks, in order to maximize spectral efficiency and hence improve the throughput of the network. Unlike previous studies assuming that accurate channel information is available for relaying and link adaptation, the novelty of our approach is to use the expected packet transmission time (ETT) and RTS/CTS exchange to estimate the quality and level of contention for the current channel. By taking into account the quality of the direct channel from source to destination and the relay channel between relay and destination, CARLA enables both source and relay terminals to adjust their transmission rates so that not only the reliability of the transmission but also the bandwidth efficiency can be improved, hence fully utilizing the diversity gain. CARLA is a simple, distributed and rate-per-link adaptation protocol requiring no modification on 802.11 PHY and MAC. Simulation results show that CARLA can achieve significant performance improvement in terms of end-to-end throughput and energy efficiency for different network conditions.