Analyzing and Optimizing Adaptive Modulation-Coding Jointly with ARQ for QoS-Guaranteed Traffic

A cross-layer design is developed for quality-of-service (QoS) guaranteed traffic. The proposed design jointly exploits the error-correcting capability of the truncated automatic repeat request (ARQ) protocol at the data link layer and the adaptation ability of the adaptive modulation and coding (AMC) scheme at the physical layer to optimize the system performance. The queuing behavior induced by both the truncated ARQ protocol and the AMC scheme is analyzed with an embedded Markov chain. Analytical expressions for performance metrics such as packet loss rate, throughput and average packet delay are derived. Using these expressions, a constrained optimization problem is solved numerically to jointly determine the retry limit for the truncated ARQ protocol as well as the prescribed packet error rate for the AMC scheme so that the overall system throughput is maximized under the specified QoS constraints.