We propose a new cooperative Medium Access Control (MAC) protocol in the context of fixed wireless networks. The protocol implements on-demand cooperation and a selection of the best relay. Hence, cooperation between a source terminal and a destination terminal is activated only when needed. In that case, only the best relay among a set of available terminals is retransmitting the source message to the destination terminal. We improve this typical approach using three additional features. First, we use a splitting algorithm to select the best relay. This ensures a fast selection process. Moreover, the duration of the selection process is now upper bounded by a known value. Second, only terminals that can improve the direct link are allowed to participate to the relay selection. By this mean, inefficient cooperation is now avoided. Finally, the destination terminal discards the source message when it fails to decode it. This saves processing time at the relay candidates. We prove that the proposed protocol achieves an optimal performance in terms of Diversity-Multiplexing Trade-off (DMT).
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