Gaussian (dirty) multiple access channels: A compute-and-forward perspective

Lattice codes are applied to the two-user Gaussian multiple access channel (MAC) combined with a modified compute-and-forward transmitting scheme. It is shown that non-corner points on the boundary of the capacity region can be achieved by decoding two integer sums of the codewords, which can be viewed as a generalization of the well-known successive cancellation decoding. A similar idea is then applied to the so-called dirty MAC where two interfering signals are known non-causally to the two transmitters in a distributed fashion. Our scheme recovers previously known results and gives new achievable rate regions. The proposed scheme can be extended to the case with more than two users.

I. Introduction

Recent results on lattice codes applied to Gaussian networks show remarkable advantages of their linear structure which random codes do not possess. In particular the compute-and-forward scheme [1] demonstrates the idea that sometimes it is better to first decode sums of codewords than the codewords individually.