Soft decision-based iterative interference cancellation (IIC) in group-wise STBC (G-STBC) MIMO systems

In this paper we present our study on soft decision based iterative interference cancellation (IIC) for group-wise space-time block coded (G-STBC) multiple-input multiple-output (MIMO) systems. In such a MIMO system, the transmission antennas are partitioned into several groups, and each group transmits independent data streams which are individually STBC encoded. The minimum number of receives antennas required is the same as the number of antenna groups at the transmitter. We first give a brief overview on the zero-forcing interference suppression (ZFIS) and the hard decision based IIC schemes. We then propose a soft decision based IIC scheme. The soft decision functions for BPSK, QPSK, 16QAM and 64QAM modulated signals are derived based on the maximum likelihood detection (MLD) criteria. For a 4 /spl times/ 4 G-STBC MIMO system with two groups, simulation results show about 2 dB performance gain for BPSK and QPSK signals, and 1.2 dB for 16QAM and 64QAM modulated signals, for the soft decision based IIC when compared with hard decision based IIC.