A design for an EXIT chart based scheduling and rate control for multi-user MIMO systems

This paper proposes a scheduling and adaptive rate control scheme for multi-user multiple-input multiple-output (MIMO) systems in the uplink, designed to improve system throughput in single-carrier broadband wireless systems exploiting a frequency domain soft canceller with minimum mean square error (FD-SC/MMSE) turbo equalizer. Aiming at the reduction of computational burden involved in the scheduling and adaptive rate control while maintaining high throughput efficiency, scheduling including a stream selection is first conducted in the base station (BS) based on the expected signal to noise power ratio (SNR) under an assumption that the turbo receiver is converged. The BS then conducts a coding rate optimization for each scheduled stream to maximize the throughput efficiency. A main contribution is to reveal a mechanism that the convergence property is controlled to maximize the throughput efficiency by a prediction of the iterative behavior based on extrinsic information transfer (EXIT) trajectory which is predicted from channel transfer functions and a window control proposed in this paper. Computer simulation confirms that the achievable average system throughput can be significantly improved by the proposed scheme.