Relay cooperation in multiaccess networks

Cooperation in communication networks results when terminals use their energy and bandwidth resources to mutually enhance their transmissions. Cooperation can be induced in many ways and each approach entails a different tradeoff of power, bandwidth, complexity, and costs to achieve spatial diversity gains characteristic of antenna arrays. In this dissertation, we study a specific cooperative network---a multiaccess relay channel (MARC) where cooperation is induced via a dedicated relay node in a network where multiple users communicate with one destination.;We extend the relaying strategies of decode-and-forward (DF), compress-and-forward (CF), and amplify-and-forward (AF) to the MARC. Specifically, for DF we show that real-time decoding at the destination using a sliding-window incurs a rate loss relative to an offline backward decoding technique. We develop an offset encoding technique that improves sliding window decoding and achieves the corner points of the backward decoding rate region with significantly smaller delay.;Next we compare two approaches to inducing cooperation in a multiaccess channel. In one approach we allow the users to cooperate while in the other we induce cooperation via a relay when the users cannot or do not cooperate. Using the total transmit and processing power consumed at all nodes as a cost metric, we compare the DF and AF sum-rates and outage probabilities for the two networks. Our results show that cooperation is most desirable in the regime where processing power is significantly smaller than the transmit power. We also show that relay cooperation is on average more energy efficient than user cooperation.;Finally, we develop a capacity result for the MARC. The MARC belongs to a class of multi-terminal networks whose capacity is, in general, not known. For a degraded Gaussian K-user MARC, we use max-min optimization techniques to show that DF achieves the K-user sum-capacity.