A simple slicer for soft detection in Gray-coded QAM-modulated MIMO OFDM systems

Gray coding is one of the most widely adopted symbol-to-bit mapping systems. In this paper, we propose a technique that exploits its structure to reduce the complexity of the dimension reduced (DR) soft MIMO detector [1]. The proposed technique translates each coded bit of prior information into an offset for determining thresholds for one coded bit. This effectively reduces the number of Euclidean distance calculations by one dimension, something taken for granted when no prior information is present. This design is optimal for detecting QPSK constellation and incurs only a trivial performance loss of less than 0.1 dB for 16QAM and 64QAM.