Optimal Power Control for Multi-User Relay Networks over Fading Channels

In energy-constrained wireless networks such as sensor networks, it is important to maximize power efficiency by minimizing power consumption for a given quality of service such as the data rate; it is equally important to evenly or fairly distribute power consumption to all nodes to maximize the network life. In this paper, we develop optimal power control methods to balance the tradeoff between energy efficiency and fairness for wireless cooperative networks where several relays assist the communication of multiple source-destination pairs. Our optimal power control policy is derived in a quasi-closed form by solving a convex optimization problem with a properly chosen cost-function. We further develop novel stochastic optimization algorithms to dynamically learn the statistics of the wireless channels on-the-fly to approach the optimal power control policy. Moreover, our power control algorithm can be implemented distributedly at relays requiring each relay to know its local channel state information. Simulation results demonstrate the merits of our power control methods.