Rate Adaptation for Cooperative Systems

Throughput is an important performance measure for data communications over wireless links. In this work, we consider joint adaptation of coding rates, modulation modes and level of cooperation for cooperative relaying to maximize the data throughput. We consider five different schemes with joint adaptation based on channel statistics: Direct transmission, conventional multihop, stationary and dynamic coded cooperation, cooperative multihop. We first obtain closed form expressions for the throughputs achieved by these schemes. Considering channel coding and modulation schemes used in wireless local area standard (WLAN) IEEE 802.11, we then compute the best throughputs and provide performance comparisons. Our results show that coded cooperation with adaptation provides substantial improvement over direct transmission and conventional multihop. Cooperative multihop enables further improvements over coded cooperation by fully exploiting cooperative diversity as well as rate adaptation and achieves the highest throughput performance among these five transmission schemes. We also observe that to maximize the data throughput in direct transmission and conventional multihop, adaptation for each hop only depends on the channel quality from the transmitter to the receiver. However, in cooperative strategies a system wide optimization is necessary.