Improving the MAC error exponent using distributed structure

Structured codes have been utilized in deriving the best known achievable rate regions in certain network scenarios. In this paper we demonstrate that structure can be also beneficial in terms of error exponents even in cases where there is no capacity gain. We use distributed structure, i.e., different users use codes which satisfy a nesting condition. Specifically, for the scalar Gaussian multiple-access channel we obtain an improvement over the best known achievable exponent, given by Gallager, for certain rate pairs.