Near-optimal joint multiuser detection for MIMO spatial multiplexing TD-HSPA evolution

In this paper, we propose a novel linear equalization and progressive group detection (PGD)-assisted constrained Viterbi algorithm (MIMO LEG-CVA) as a near-maximum likelihood sequence estimation (MLSE) approach for the multi-stream MIMO TD-HSPA+ downlink system under frequency-selective fading channels. PGD is a near-maximum likelihood (ML) detection technique that spans and intelligently prunes the set of possible transmit-symbol combinations, and provides a set of the most probable spatially-multiplexed transmit symbol candidates to a Viterbi equalizer performing set-constrained sequence estimation. Simulation results for the TD-HSPA+ system show that the proposed receiver outperforms block linear equalizers, and provides substantial performance gains that scale with complexity (in terms of the size of the candidate-set).