Joint Rate and Power Adaptation for Type-I Hybrid ARQ Systems Over Correlated Fading Channels Under Different Buffer-Cost Constraints

We present a general framework for the computation of the optimal scheduling policies for delay and overflow-constrained joint rate and power adaptations for type-I hybrid automatic-repeat-request systems. This framework can be applied to adaptive resource-allocation problems on correlated flat-fading or frequency-selective fading channels for bursty nonconstant packet arrivals. It is shown that the optimal-rate and powercontrol laws can be obtained by solving the formulated Markov decision process problems. We consider two cases for packet scheduling over wireless channels that are of significant practical importance. In the first case, we assume that the transmitter perfectly knows the channel-state information (CSI) at the beginning of the transmission. The transmitter is also provided with the decoding result for the previous transmission in terms of observation feedback at the end of the transmission. Second, we consider the scheduling problem when the transmitter does not know the CSI at the time of transmission, but it makes the transmission decision based on the history of previous transmissions and corresponding outcomes. In both cases, our objective is to minimize transmission power, and the optimal policies are computed under two different buffer-cost constraints, namely, the average buffer delay and the average packet overflow rate. The results of this paper are of importance for the development of modern wireless standards that support heterogeneous multimedia and Internet traffic with certain application-dependent-delay and packet-dropping requirements.