Delay-aware Power Adaptation for Incremental Redundancy Hybrid ARQ over Fading Channels with Memory

We investigate transmit power adaptation strategy for IR-HARQ scheme over correlated fading channels. In order to jointly analyze physical and link layers, the transmitter model incorporates a finite-size buffer that receives randomly varying traffic from a higher layer application. It is assumed that channel variations can be modeled with first order Markov chain. We show that the optimal power adaptation law under buffer delay and packet overflow constraints can be obtained using the framework of semi-Markov decision processes. The optimal policy is computed using the linear programming approach. Simulation results show that substantial power savings can be achieved if the transmission delay requirements are relaxed.