Integrating lattice space-time codes of highest rank and multiplexing over rayleigh fading channels

In this thesis, we consider the problem of finding an optimal combination of multiplexing and space-time coding over a MIMO array when a transmitter has a prior knowledge about correlation. Some existing work in this area used multiplexing and space-time coding methods as a technique to achieve capacity over a MIMO wireless channel. In this work, we consider a 2x2 lattice space-time code of highest rank and multiplex it over a MIMO system to improve the bit error rate performance. The main focus of this thesis is to address the problem of switching between spatial multiplexing and space-time coding to enhance the performance of a MIMO system. The data rate over wireless links is improved by using a MIMO system. For this type of system, the spatial dimension is exploited by using spatial multiplexing and space-time coding with diversity oriented transmission. Spatial multiplexing uses spatial degrees of freedom and space-time coding uses the antennas. To integrate them the system has to compromise to some extent in performance criterion. This thesis investigates the need to switch between the spatial multiplexing and space-time coding over space by making the instantaneous channel feedback available at transmitter. This thesis also indicates that the bit-error rate of the combination of lattice space-time code and multiplexing can be reduced when compared with the combination of Alamouti scheme and spatial multiplexing