Stochastic feedback control for spatial interference avoidance

Spatial interference avoidance is a simple and effective way of mitigating interference in multi-antenna wireless networks. The deployment of this technique requires channel-state-information (CSI) feedback from each receiver to all interferers, resulting in substantial network overhead. This paper proposes the method of distributive feedback control that intelligently allocates feedback bits over multiple feedback links and adapts feedback to channel dynamics. Using tools from stochastic optimization, the structure of the optimal control policy is characterized. Specifically, the optimal numbers of feedback bits are proved to increase with corresponding interference-channel gains and feedback is performed only when such gains are large or the transmit-CSI errors are significant. Simulation demonstrates that the proposed feedback-control design yields significant throughput gain over the conventional fixed-feedback approach especially at low mobility.