Downlink distributed beamforming through relays with imperfect CSI

Future wireless systems face challenges in supporting high-rate multimedia streaming with wide coverage area and at low power. In this paper we study cooperative MIMO systems in the context of imperfect channel estimation with per-user quality-of-service constraints with the objective of minimizing the sum transmission power at the source and relays. Simulation results quantify the different performance tradeoffs obtained in incorporating imperfect CSI into the problem formulation as a function of channel estimation accuracy.