The Diversity-Multiplexing Tradeoff for the Multiaccess Relay Channel

This paper studies the diversity-multiplexing tradeoff for the multiaccess relay channel (MARC) with static, flat fading. It develops two simple strategies, namely multiaccess amplify-and-forward (MAF) and multiaccess decode-and-forward (MDF), that help the users gain the benefit of cooperative diversity without changes in their devices. Results suggest that in the regime of light system loads, both strategies offer improved performance to each user as if no other users interfere or contend for the relay. However, they are inferior to the optimal dynamic decode forward (DDF) protocol in this regime. In the regime of heavy loads, the MARC with MAF offers better performance, and MARC with MDF degenerates into the multiaccess channel (MAC) without a relay. Moreover, the MAF protocol is optimal in the regime of high multiplexing.