Space-time multiuser detectors for TDD-UTRA: design and optimization

Linear multiuser detection (MUD) for frequency selective channels has always been considered a prohibitive computational task in CDMA systems. In time slotted CDMA, the block-type MUD involves the inversion of a large matrix that depends on the block size and on the number of users. Sub-optimal techniques are computationally efficient but show some performance degradation. The reduced complexity detectors can be either block-type or one-shot. Compared to one-shot approximation of MUD, the block-type detectors have less computational complexity and large latency. However, the tracking of channel variations within the block is not feasible with any block-type processing (e.g., for the adaptive receiver). These compelling aspects force us to use a one-shot MUD algorithm for space-time channels such as the sliding window decorrelator (SWD). Block-based MUD and SWD algorithms for TDD-UTRA systems are compared in terms of performance, computational complexity, parallelism and hardware implementation.