On the Throughput of Wireless Communication With Combined CSI and H-ARQ Feedback

In this paper, we characterize the combined channel state information (CSI) and re-transmission feedback on wireless communication. Feedback, often assumed free, has traditionally been used to either learn the channel state, or to request the re-transmission of a failed reception. We propose here a generalized framework for feedback that captures the channel time-variation. We consider two-way communication model where all the resources needed for training, feedback (CSI and automatic repeat request), and data. In order to maximize the throughput and optimize resource allocations, we provide the expressions of outage probabilities for different rate/power adaptation and re-transmission protocols. The simulation results show that, besides signal-to-noise ratio (SNR) and Doppler, the optimal pilot overhead depends on whether we are using rate/power adaptation and the number of re-transmissions. We also prove that in slow-fading channels with high SNR regimes, varying the rate provides the best throughput. When dealing with fast time-varying channels and low SNR regimes, using constant power and rate gives the best throughput performance.