Limiting the constellations subjected to ML detection in OFDM/SDM systems

This paper presents a signal detection scheme for orthogonal frequency division multiplexing (OFDM)/space division multiplexing (SDM) that can realize high-rate wireless LANs offering over 100 Mbit/s. The signal detection scheme separates each subcarrier signal from the multiplexed OFDM/SDM subcarrier signal. In this paper, we propose a new signal detection scheme based on a reduced dimension technique, which limits the number of constellations subjected to maximum-likelihood detection (MLD) for OFDM/SDM systems. Considering 64QAM OFDM/SDM, the proposed scheme uses only 64 combinations of constellations regardless of the number of data streams. It is shown that the proposed scheme greatly suppresses the negligible degradation, in terms of required E_b/N₀, in two-by-two OFDM/SDM transmission, compared to conventional MLD. i.e. brute-force MLD. In addition, we show that the proposed scheme suppresses the degradation in required E_b/N₀ by approximately 1.5 dB in three-by-three OFDM/SDM transmission at PER=0.01.