Adaptive Hybrid Automatic Repeat Request (ARQ) with a Novel Packet Reuse Scheme for Wireless Communications

In wireless communication systems, selective repeat automatic repeat request (SR-ARQ) with code combining is a good solution for fading channels. However, performance of such scheme varies with different packet lengths. In this paper, we propose an adaptive hybrid automatic repeat request protocol (AH-ARQ) which continuously estimates throughput efficiency of different packet lengths with average number of packet transmission in different decoding conditions while combining received packets. By estimating channel condition and adapting packet length, throughput efficiency can be maximized. Other than former studies, throughput efficiencies of different packet lengths can be predicted without knowledge of channel condition such as Doppler frequency or vehicle speed which needs extra modification or device to the system because average bit error probability can be seen as constant for different packet lengths in the same channel condition. We also consider the influence of observation interval (OI) and difference between throughput efficiencies of different packet lengths (DTE). With optimized OI and DTE, simulation result shows that AH-ARQ can adaptively sense change of channel condition and maximize the throughput efficiency continuously in spite of its simplicity.