Throughput Analysis of Arq Protocols in Rayleigh Block Fading Environments

Block fading is a popular channel model that approximates the behavior of different wireless communication systems. Automatic-Repeat Request (ARQ) protocols are used to provide reliable communications in wireless networks. In this paper, the throughput of basic and hybrid ARQ protocols over Rayleigh block fading channels is derived. The throughput is computed for different modulation schemes and for a wide variety of channel memory length. Results show that longer channel memory improves the performance of basic ARQ protocols whereas it degrades the performance of hybrid ARQ protocols. This is due to the fact that the decoder in a hybrid ARQ protocol utilizes the diversity provided by the independent fading blocks to average over the channel behavior and to obtain a good performance. Furthermore, the throughput improvement obtained in basic ARQ protocols decreases with increasing the memory length.