The Study Of Closed-loop Quasi-orthogonal Space-Time Codes

Space time codes (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 date rates without spreading the system bandwidth and increasing the transmit power in wireless communication systems. As a kind of new technique, space time coding attracts many investigators and has also become popur in wireless communication. Not only used in 3GPP, but also space-time coding is used in other wireless communication systems. To preserve the full symbol rates, however with a small lose in diversity Quasi-orthogonal space-time block codes (QOSTBC) have been developed on the basis of OSTBC.In this thesis, the transmission rare one space-time from quasi-orthogoal design for the even number of transmit antennas and an arbitrary number of receive antennas is discussed. At first, it introduceds three kinds of traditional QOSTBC and their equivalent channel models, the interference parameter and its common properties.Most OSTBC and QOSTBC are designed assuming that the transmitter has no knowledge about the channel. However in some applications, the transmitter can exploit channel state information (CSI) to improve the overall performance of the system. In this thesis, the improved transmit antenna shuffling (TAS) scheme can increase the ergodic capacity of QOSTBC even if there has high correlation between transmit antennas. And it gives the upper bounds of ergodic capacity of QOSTBC with the imporoved TAS scheme. The numerical results show that the derived analytical results agreed with the simulations.At last, the proposed TAS scheme is used to minimize the Bit Error Ration (BER) with the liner zero forcing(ZF) and Maximum-Liklihood(ML) receiver. We give a simple ML algorithm withouting increasing the decoding complexity, compare its BER with the traditional QOSTBC's and the QOSTBC's of constellation rotation. Only send partial channel state information back from the receiver to the transmitter, the proposed TAS scheme can achieve almost the same performance as the ideal full diversity.AS for the ZF receive,we analytized the relations between interference parameter with the number of receive antennasIn conclusion, this thesis take the predecessor's theory study on QOSTBC as the basis, mainly discuss the ergodic capacity and the Bit Error Ration (BER) of QOSTBC, the improved TAS scheme is used for the system with multiple transmit and receive antennas. The theory analytical and simulations results proved the feasibility.