科研之友
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摘要
Selection cooperation is an attractive cooperative strategy for its simplicity and automatic repeat request (ARQ) mechanism can bring additional diversity benefit for wireless networks. In this paper, we combine the distributed selection cooperation protocols with ARQ mechanism to develop more powerful cooperative schemes for delay-tolerant wireless networks and analyze their performance from the perspective of diversity-multiplexing-delay (D-M-D) tradeoff. For small networks where any two nodes have direct links, we investigate the general ARQ scheme which directly extends the selection cooperation protocol with single round of feedback to multiple rounds. We show that the D-M-D tradeoff is determined by the ability of relays in signal combining and demonstrate that allowing relays to perform combining reception can achieve optimal D-M-D tradeoff. Then we propose a simplified scheme which greatly reduces the number of feedbacks and almost achieves the optimal performance. For large networks where direct links are limited in the neighbors of each node, we present a diffusion ARQ protocol which can effectively exploit the channels of nodes that have no direct links with the source. The D-M-D tradeoff analysis and simulation results demonstrate the significant performance improvement of all the proposed schemes.
