Differential Unitary Space Time Coding Techniques In MIMO Wireless Communication System

Space-time code ( STC ) ,which based on multi-antenna at the transmitter and receiver, is the combination of channel coding and antenna diversity techniques. It can increase system capacity and data rates without spreading the system bandwidth and increasing the transmit power in wireless fading channel, satisfy the desire of the future wireless communication systems. Different with the conventional STC, differential Space-time code can keep good performance when neither the transmitter nor the receiver knows the channel state information in Rayleigh flat fading channels. This thesis first discussed the design criterion, en/decoding scheme and the characteristic of each kind of space-time coding techniques, analysed and compared the performance. Then we studied the optimal diversity product constellation structure criterion of differential unitary space-time coding (DUSTC) in high signal to noise ratio situation, analysed the constellation structure and en/decoding algorithm of three DUSTC which based on the group structure, the orthogonal design and the matrix rotation in detailed, simulated and compared the performances.The traditional DUSTC with only one level of amplitude are considered and this may degrade the performance of code. This dissertation proposed a new code which named Multi-Level DUSTC through relax the constraint of amplitude to allow the information symbols to have multiple level and keep the fast maximum likelihood (ML) decoding algorithm. The minimal distance between constellations can be enlarged and the constellation diversity product is enhanced. Simulation results demonstrate the improved new DUSTC outperforms the original differential unitary space-time code, and the Multi-Level DUSTC is preferable choice for the future wireless communication system.