On Differential Unitary Space-Time Codes

Recent advances in communications across multiple-antenna wireless commuincation links show that space-time coding(STC) can have very high channel capacites. A new class of STC called unitary space-time signals is proposed that is well tailored for Rayleigh flat-fading channels where neither the transmitter or the receiver knows the fading coeffients.In this thesis, we briefly introduce the development of STC, and study the characteristic and the simulations models of two kinds of fading channel. We discuss some details about STC, including layered space-time coding, space-time trellis coding and space-time block coing. Space-time coding can support very high data rates with low error propabilities, especially when the wireless channel response is known at the receiver. However, the assumption that the channel is known is questionable in a rapidly changing mobile environment, or when multiple transmitter antennas are employed. Unitary space-time codes and differential unitary space-time codes don't need any channel information. Compared with the unitary space-time codes, DUSTC not only dosen't need any channel information, but also has simple constellation structure and coding-decoding algorithm.We discuss the unitary space-time codes briefly and study the details of the DUSTC, including the fundamental differential transmission and receiver equation, the constellation design based group theory, and parameters searching algorithm. The parameters searching and simulations results is proposed. Then we analyze the exact PEP and union bound of SEP of the DUSTC. And the conclusion that different range of SNRs needs different searching criteria is proposed. Finally, we search these parameters in the group constellation based on union bound criteria, and simulate the performance in the Rayleigh fading channel. The simulation results show that the union bound criteria is pretty tight at medium range SNRs, and the non-integer parameters can improve the performance slightly.