ON THE FACTOR-OF-2 BOUND FOR GAUSSIAN MULTIPLE-ACCESS CHANNELS WITH FEEDBACK

It was recently shown by Pombra and Cover that the maximum achievable throughput (sum of rates of all users) of a Gaussian multiple-access c hannel with feedback is at most twice that achievable without feedback . We prove a somewhat stronger result which establishes the factor-of- two bound not only for the total throughput but for the entire capacit y region as well. Specifically, we show that the capacity region of a Gaussian multiple-access channel with feedback is contained within twi ce the capacity region without feedback.