Joint Interference Cancellation and Channel Shortening in Multi-User MIMO Systems


Roopsha Samanta, Robert W. Heath Jr., and Brian L. Evans


Submitted to IEEE Transactions on Vehicular Technology in December 2004.


In this paper, a two-stage receiver structure is presented for interference cancellation in multiuser multiple-input multiple-output (MIMO) systems in frequency-selective channels. The framework is developed for spatially-multiplexed systems, and is used for suppressing interference arising from asynchronous users, self-interference from the desired user.s antennas, and channel-induced intersymbol interference (ISI). A space-time equalizer is used in the first stage for joint coantenna/cochannel interference suppression and shortening of the effective channel for each transmit stream of the desired user, without equalization of ISI. The channel shortening, combined with independent detection, helps reduce the complexity of the second stage Viterbi equalizer, which is used for separate ISI equalization for each of the streams. Three algorithms are proposed for determining the coefficients of the spacetime equalizer using a direct training data-based approach. The objective functions are based on the knowledge of the training sequences of the desired user; they do not require estimation of the cochannel interferer.s channel and enable mitigation of asynchronous interfererence. Simulation results show good symbol error performance as compared to existing algorithms in single-user MIMO systems and in two-user systems with both synchronous and asynchronous MIMO interferers.

This preprint is available upon request.