Performance Analysis and Enhancement of Cooperative Retransmission Strategy for Delay-Sensitive Real-Time Services

As a very promising technique, multi-hop relay has been considered in many wireless networks. It can take advantage of the inherent broadcasting nature of wireless transmission and facilitate cooperative communications. In this paper, we develop an effective analytical framework to study the delay performance of cooperative retransmission strategies. All neighbor nodes overhearing the in-progress transmission cooperate in a distributed manner and contribute to retransmissions. In particular, we focus on the application of cooperative retransmission for delay-sensitive real-time services. Based on the proposed analytical framework, the cumulative distribution function of packet transfer delay can be numerically evaluated. Accordingly, we investigate the delay outage probability (i.e., the probability of violating the maximum delay bound), which is an essential statistical quality-of-service (QoS) metric for real-time services. Further, an enhancement approach is proposed to reduce unnecessary power consumption on retransmissions. It dynamically adapts the transmission probabilities of all participating nodes, depending on current retransmission count. As shown in the numerical results, the adaptive cooperative strategy can achieve a better trade-off between satisfying delay constraint and minimizing total power consumption.