Rate Allocation for K-user Mac with Turbo Equalization

A primary objective of this paper is to examine the achievable rate region of frequency selective K-user multiple access channels (MACs) with soft-cancelling frequency domain minimum-mean-squared-error (SC FD-MMSE) turbo equalization. With the aid of the knowledge about the extrinsic information transfer (EXIT) characteristic of the equalizer, we study the problem of determining the optimal rate allocation (RAAL) to the K users, for which the sum rate is maximized, and introduce a heuristic approach based on the dynamic programming principle for solving this optimization problem. We also propose a practical code selection algorithm for the RAAL to the K users given the multidimensional EXIT functions of the equalizer. It is shown through simulations that with SC FD-MMSE turbo equalization, substantial throughput gain can be achieved with the proposed RAAL technique over automatic repeat request with fixed coding rate.