Multiuser Diversity in Wireless Networks: A Diversity-Multiplexing Perspective

We derive a simple characterization of the diversity-multiplexing (D-MG) tradeoff in three multiuser scenarios -multiple access, broadcast and relay assuming channel knowledge at the transmitters. Specifically, we study the D-MG tradeoff of protocols in literature that opportunistically use the channel knowledge to maximize the information rate. We show that for the multiple access channel with K users, a feedback of log K" bits is sufficient to maximize the multiuser diversity gain. The multiuser diversity gains in all three channels are obtained without explicit cooperation between users.