Scalable Feedback Protocol Asymptotically Achieving Broadcast Channel Sum-capacity

Distributed feedback-protocols are developed for multi-user diversity to (a) keep the feedback amount fixed regardless of the number of users (denoted as U); (b) maintain identical protocols; (c) asymptotically achieve sum-capacity; and (d) minimize power consumption. With proposed methods, the users with signal-to-noise ratio (SNR) larger than a threshold T _k send feedback messages at slot k. Tk is designed for the probability of feedback transmission at any slot to be p. With proper p, the probability of feedback from the user with the largest SNR is prescribed probability s regardless of U. Then, all four objectives are achieved with the proposed feedback methods.