Outage minimization and fair rate allocation for the multiple access relay channel

We consider a block fading multiple access relay channel (MARC) where K users communicate with a single destination in the presence of Q ≥ 1 half-duplex relays. Each relay employs a successive group decoder with a specified complexity constraint and a decode and forward (DF) protocol. We design an outage minimizing relaying strategy for the scenario where no channel dependent feedback is possible between the destination and any user but a limited amount of such feedback is possible between the destination and each relay. We also design a rate allocation algorithm which yields the symmetric fair rate allocation. Remarkably, even though the outage minimization and rate allocation algorithms use low-complexity ‘greedy’ or myopic sub-routines at the relays, they achieve globally optimal solutions.