Quasi-orthogonal Space-time Block Codes And Their Decoding Algorithm

Space time block code is an important skill of channel code in MIMO system. Because the space time block code (STBC), which can give full-diversity, have simple structure and decoding algorithm in space time code ,it got extensive research in recent years. Because the rate of orthogonal space time block code (OSTBC) can not get 1 when the number of transmit antennas is over 2. So the space time block code, which can improve the transmission rate only sacrifice part orthogonal feature, is worth to research deeply.In research, it showed that the quasi-orthogonal space time block code (QOSTBC) could get full transmission rate in sacrificing part orthogonal feature. In the QOSTBC for research object, based on researching deeply the criterion of space time code, we put forward new QOSTBC structures and the decoding method.First, according to the code criterion and the concept of QOSTBC, A new QOSTBC for four transmits was proposed, to improve the code performance, a new rotated QOSTBC is obtained when input signal is preprocessed by a rotation transformation. The numerical simulation results show that the performance of the unprepossessing QOSTBC is similar to the known QOSTBC. However, BER performance of the rotated QOSTBC is improved obviously.Second, according to the rank criterion, to a full-rate full-diversity QOSTBC is obtained by matrix rotation processing on the conventional QOSTBC. The numerical simulation results show that the performance of the full-rate full-diversity QOSTBC can get better performance.Last, according to the sphere decoding (SD) algorithm, we propose an improved SD, and then it is applied to QOSTBC decoding. The numerical simulation results show that at the expense of the decoding performance, the decoding complexity is obviously deduced.