Three-user Gaussian multiple access channel with partially cooperating encoders

A three-user Gaussian multiple access channel (MAC) with encoders partially cooperating over a ring of finite-capacity uni-directional links is studied. The model is a simple extension of the classical two-user MAC with conferencing encoders. Upper and lower bounds on the maximum achievable common rate are derived. The lower bound is attained via a novel multi-layer cooperative strategy. The bounds are tight for a certain range of values of the inter-user link capacity. Numerical results are provided to corroborate the analysis.