Throughput and Efficiency Analysis of Network-coded HARQ for Two-way Wireless Systems
Due to the explosive increase of wireless subscribers, it becomes more crucial to efficiently use the limited spectrum resources. To improve spectral efficiency, this study explores network-coded (NCed) automatic repeat request (ARQ) in two-way wireless systems. NCed-ARQ has been proved effective in multi-cast and broadcast channels by utilizing the side-information overheard during retransmissions. However, most wireless networks are two-way where each node transmits and receives. In two-way wireless systems, more side-information can be used to enhance the throughput performance with network coding, which has not received much attention. In this study, we propose a new NCed-ARQ scheme with reverse-link assistance to fully utilize the side-information generated in two-way wireless systems. We consider two typical two-way wireless system models. One is multi-access broadcast channel with one base-station and multiple users. In the second one, a relay is added as a low-cost solution for increasing the capacity. We derive the expressions of throughputs for both models. Our simulation results show that the proposed scheme achieves higher throughputs in both systems, especially for low/moderate SNRs. Additionally, NCed-ARQ requires more acknowledgments from users. The effect of the extra feedback, especially on the uplink of a two-way system, remains unclear. We also study the extra feedback required for NCed-ARQ and the resulting packet efficiency. With simulation, we reveal the trade-off in the throughput when considering the extra feedback.
Smida, Purdue University.
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