Study Of Space-Time Block Codes

Without increasing the system bandwidth or transmit power,Multiple-Input Multiple-Output (MIMO) technology can increase channel capacity and spectral efficiency. Space-time coding is a key technology in MIMO system. Generally, Space-time coding can be classified into Space-Time Block Codes (STBC) and Space-Time Trellis Codes (STTC). Due to the attractive properties of STBC of having full transmitted diversity and a decoupled maximum-likelihood (ML) decoding algorithm, the STBC has received increasing attention. However, previous studies showed that the data rate of STBC is low.Firstly, based on the radio channel propagation characteristics, the channel capacity and different models of MIMO system including the Single-Input Single-Output (SISO), Multiple-Input Single-Output (MISO) and Single-Input Multiple-Output (SIMO) are analyzed in this paper. Secondly, from the perspective of capacity, the performances of several classical STBC including Orthogonal Space-Time Codes (OSTBC) and Quasi-orthogonal Space-Time Codes (QOSTBC) are presented, respectively. Finally, for the three transmit antennas or four, the non-orthogonal STBC with high rate and full diversity are studied. Referring to the schemes of Alamouti codes and QOSTBC, this paper proposes two novel coding schemes. The code rate of the proposed coding schemes are both 2 bits/s, which means that the two proposed coding schemes can transmit eight symbols just in four time slots. For the two proposed coding schemes, in order to reduce the decoding complexity, the conditional ML algorithm is used for one, and block decoding algorithm based on the equation of the ML is used for the other. The mutual information of the proposed coding schemes are analyzed in this paper, respectively. The results of simulation prove that one of the proposed coding schemes is with more excellent BER performance and the mutual information between the transmitters and receivers of the other coding scheme are higher.