Dependence Balance and the Gaussian Multiaccess Channel with Feedback

Dependence balance bounds of Hekstra and Willems are generalized and refined. The new bounds are applied to the K-user multiaccess channel (MAC) with output feedback, and they are shown to establish the feedback sum-rate capacity for the Gaussian MAC when all users have the same per-symbol power constraints. The sum-rate capacity is achieved by Fourier modulated estimate correction. The feedback sum-rate capacity is shown to improve the no-feedback capacity by only log log K nats per use for large K. The new bounds also improve on cut-set bounds for asymmetric powers and rates.