Transmission schemes for time-varying wireless channels with partial state observations

In this paper, we are interested in developing a control algorithm or transmission scheme for wireless data communication over time-varying channels with memory that determines when to attempt a transmission and at what power level, so as to achieve a suitable balance between throughput and energy consumption; and studying the effect of channel memory on the performance, design, and structure of this scheme. The channel state is not directly observable, and thus the transmission decisions must be based on partial or incomplete channel state information, provided to the user by the base station over a feedback channel. More specifically, we assume that the delayed channel state information is provided to the sender at the end of those time slots during which packet transmissions are made. We cast the problem as a partially observable Markov decision process. Despite the difficulty associated with the incomplete channel information, we obtain the optimal transmission scheme, which can be interpreted as a back-off rule: at the end of the transmission, depending on the channel quality during the past time slot, the transmission may be suspended for some time slots, which can be computed in advance. Numerical results are also provided.