Distributed power control for cooperative diversity in the MAC channel

We consider a multiple access MAC fading channel with two users communicating with a common destination, where each user mutually acts as a relay for the other one as well as wishes to transmit his own information as opposed to having dedicated relays. We wish to evaluate the usefulness of relaying from the point of view of the system's throughput (sum rate) rather than from the sole point of view of the user benefiting from the cooperation as is typically done. We do this by allowing a trade-off between relaying and fresh data transmission through a resource allocation framework. We develop capacity expressions for our scheme and derive the rate-optimum power allocation in closed form for distributed frameworks. In the distributed scenario, partially statistical and partially instantaneous channel information is exploited. Our results indicate that the sum rate is maximized when both mobiles act selfishly.