Abstract

There are many technologies being considered for the next generation of wireless communications. Of these technologies, multi-input multi-output (MIMO), orthogonal frequency division multiplexing (OFDM) and Walsh spreading are drawing the most attention. Although a lot of research has been done in this area, it has not been decided yet as to which technology or combination of the technologies will be used in future wireless generations. The new generation will have to support high data rates and provide excellent performance in order to accommodate several multimedia services. In this thesis, a MIMO-OFDM system that employs Walsh sequences as block coding is designed. Simulation studies show that the proposed system exhibits high performance and comparisons show that it has low complexity compared to some of the previous systems. Two configurations are considered for the proposed system. The first configuration combines Vertical-Bell Labs Layered Space-Time (VBLAST), OFDM and Walsh block coding, for which a simplified implementation scheme for the proposed coding is presented. The system is investigated through extensive computer simulations using different system parameters and channel conditions. The proposed system is compared to some of the existing systems in terms of performance as well as computational complexity. The second configuration integrates space-time block coding (STBC), OFDM and Walsh block coding. In contrast to VBLAST, which aims to increase system capacity and data rates, STBC improves the system's performance through multipath diversity. The performance of the system is studied through computer simulations and the computational complexity of the system is also compared to some typical STBC systems from previous research. The simulations and comparisons of both configurations of the proposed system show its superiority in terms of performance and computational complexity to previous systems. Finally, to emulate real-life scenarios, the performance of the proposed system is also investigated using some common channel estimation techniques. It is shown that by utilizing a preamble of training symbols, the proposed system provides a satisfactory performance for both the configurations.