Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks

This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then optimize an AMC scheme which directly satisfies a prescribed packet loss rate constraint at the data-link layer. The results indicate that utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the spectral efficiency compared with the system that employs AMC alone at the physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme outperforms the fixed rate counterpart when the transmission modes at the source and relay are chosen based on the channel statistics. This in turn quantifies the possible gain achieved by joint design of AMC and ARQ in wireless relay networks.Comment: 5 pages, 4 figures, To appear in the Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems (ISWCS), Rykevick, Island, Oct 200

Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay Networks

This paper presents a cross-layer approach to jointly design adaptive modulation and coding (AMC) at the physical layer and cooperative truncated automatic repeat request (ARQ) protocol at the data link layer. We first derive an exact closed form expression for the spectral efficiency of the proposed joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance measure, we then optimize an AMC scheme which directly satisfies a prescribed packet loss rate constraint at the data-link layer. The results indicate that utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the spectral efficiency compared with the system that employs AMC alone at the physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme outperforms the fixed rate counterpart when the transmission modes at the source and relay are chosen based on the channel statistics. This in turn quantifies the possible gain achieved by joint design of AMC and ARQ in wireless relay networks.Comment: 5 pages, 4 figures, To appear in the Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems (ISWCS), Rykevick, Island, Oct 200

Rate Adaptation for Cooperative Systems

Abstract — 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. I