Guided Search MIMO Detectors aided by Lattice Reduction under Correlated Channels

The conventional detector (matched filter) becomes inefficient in MIMO systems demanding high data throughput and/or subject to interference and/or under correlated channels. The bit error rate performance or system capacity under conventional detection will be substantially degraded when the spatial diversity provided by multiple antennas cannot be fully exploited and the detection process is unable to efficiently separate the signal from each antenna. The solution discussed in this paper seeks to establish more efficient detectors for MIMO systems with the aid of the Lattice Reduction technic. These detectors use information from the interfering signals in a way to improve the signal detection in the antenna of interest, thus providing advantages over the conventional system, at the expense of increasing complexity. The focus of this paper consists in comparing the characteristics of three sub-optimal detectors, previously analyzed in [1], based on the maximum-likelihood function and the guided search principle. Especially, the complexity vs performance trade-off for the sphere detector (SD), the QR decomposition-based detector (QRD) the greedy search detector (GSD) and its variants aided by the Lattice Reduction are compared. We have considered the performance-complexity tradeoff as a main figure-of-merit of sub-optimal MIMO detectors under Rayleigh correlated fading channels.