Spatial Precoder Design for Differential Space-Time Coded Systems: Based on Fixed Parameters of MIMO Channels

In this paper, we introduce the novel idea of linear spatial precoding based on fixed and known parameters of MIMO channels to improve the performance of differential space-time coding schemes. Antenna spacing and antenna placements (geometry) are considered as fixed parameters of MIMO channels, which are known at the transmitter. This new linear spatial precoding scheme exploits the antenna placement information at both ends of the MIMO channel to ameliorate the effect of non-ideal antenna placement on the performance of differential space-time coded systems. With this design, the precoder is fixed for fixed antenna placement and the transmitter does not require any feedback of channel state information (partial or full) from the receiver. A second precoding scheme is proposed by exploiting the non-isotropic scattering distribution parameters of the scattering channel. Unlike in the first scheme, the second scheme requires the receiver to estimate the non-isotropic distribution parameters and feed them back to the transmitter. Simulation results show that first scheme provides significant performance improvements at low SNRs and the second scheme provides significant performance improvements both at low and high SNRs.