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A Proposal of QRM-MLD for Reduced Complexity of MLD to Detect MIMO Signals in Fading Environment

This paper proposes symbol replica candidates reduction type QRM-MLD using simple quadrant detection for 4-by-4 MIMO/SDM system with 16 QAM. Though MLD is known as the optimal SDM signal detection algorithm, its computational complexity is exponential in the number of transmit antennas (van Zeltst et al). As the signal detection algorithm that can greatly decrease its computational complexity, QRM-MLD with adaptive selection of surviving symbol replica candidates is proposed (Higuchi et al.). While this algorithm is using multiple quadrant detections and symbol ranking, we propose a simple algorithm in terms of operation though the number of calculation of branch metrics is larger than that of its algorithm. In this paper, we compare the BER performance and computational complexity of the proposed scheme with that of conventional QRM-MLD and MLD.