Delay fairness aware ARQ protocol for two-user cooperative networks

In this paper, the fairness issue of delay performance for the ARQ protocol in two-user cooperative system is investigated. Relay policy between users are constrained by their own delay performance. When the delay for two users vary greatly, the system will reduce to three-node cooperation networks. Short-delay user will always provide relay service to the long-delay user if necessary to quicken the transmission of that user. The calculation for optimal queue length thresholds to schedule relay service is also given and numerical results show that the proposed delay-aware ARQ can maintain delay fairness between two users significantly with only a small delay increase to the short-delay user.