ABSTRACT
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 and transmits 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. Specifically, We propose a cooperative transmission scheme allowing each user to allocate a certain amount of power for his own transmitted data while the rest is devoted to relaying. The underlying protocol is based on amodification of the so-called nonorthogonal amplify-and-forward (NAF) protocol [1].We develop capacity expressions for our scheme and derive the rate-optimum power allocation in closed
form for centralized and distributed frameworks. In the distributed scenario, partially statistical and partially instantaneous channel information is exploited.
