Simulation Research On Space-Time Block Coding And Its Combination With Beamforming Technique

Space-time coding is a channel coding technology based on multiple-input multiple-output(MIMO) systems, which not only can greatly improve wireless communication system capacity, but also can extremely increase the spectrum efficiency by providing diversity gain and coding gain without sacrificing bandwidth. Therefore, space-time coding can efficiently solve the problem of limited bandwidth and will be used in the future of high speed wireless data communication systems.This thesis mainly studies space-time block coding(STBC), including orthog-onal space-time block coding(OSTBC), quasi-orthogonal space-time block coding (QOSTBC), rotating STBC and the issues combining with beamforming. The main content of the thesis is as follows:First of all, the orthogonal design and decoding algorithm of QOSTBC are studied. It has simply encoding and decoding algorithm and can achieve full-rate transmission, so system perfomance is significantly improved. But when the transmit antennas are more than two, OSTBC can't be transmitted with full-rate.Secondly, the thesis lays emphasis on the study of improved STBC, including QOSTBC, matrix rotation STBC and constellation rotation STBC. Givens rotation and constellation rotation methods are used to construct improved schemes of QOSTBC, this not only can eliminate the interference of QOSTBC, but also can access to full rate and full diversity. The system performance is futher improved. The simulation analysis shows that, some different QOSTBC coding matrix are offered to achieve full rate transmission, but the performance is the same; Rotating QOSTBC by encoding improved greatly improve the system performance. Furthermore, great attention is paid on the paired maximum likelihood decoding algorithm(DML), fast maximum likelihood decoding algorithm(FML), QR decom-position algorithm based on maximum likelihood decoding. Simulation analysis shows that, fast decoding algorithm has the worst performance; in the premise of almost without sacrificing system performance, the QR decomposition decoding scheme reduces the decoding complexity, providing nearly the same performance as maximum likelihood decoding.At last, STBC combinng with beamforming is studied. STBC can be effective against multi-path fading,but can't suppress various kinds of interference. And the beamforming technology can enhance the disired signal, and restrain the co-channel interference between users. Simulation analysis shows that, the system performance of STBC combined with beamforming is superior to single STBC system; Meanwhile, improved QOSTBC combined with beamforming showed by this thesis further improves the system performance.So system performance can be greatly improved by effectively combining STBC with beamforming technology.