Research On The Combination Of Layered Space-time Code And Orthogonal Space-time Block Codes In Multi-antenna Systems

The MIMO technology, which improves the performance of BER and spectrum efficiencyof wireless communication systems, is widely considered one of the key technologies fornext-generation mobile communication. It has widely applied to space-time technologies at thetransmitter in recent years, where bell labs layered space-time coding (BLAST) and space-timeblock coding (STBC) are the two main space-time technologies. However, BLAST emphasizedon spatial multiplexing to improve capacity of the system; and STBC focused on space diversityto improve performance of the system. In view of the above problems, in order to make theMIMO system have the abilities of space diversity and space multiplexing simultaneously,assuring that the communication system has higher data rate and antifading ability, this paperconcentrates on the combination of VBLAST technology (vertical BLAST) and dual antennaSTBC technology (also called Alamouti schedule) at the transmitter in the MIMO system. Tomaintain the research goal, the paper starts in the three levels as the following:1. Deep studying the transmitting architecture of the BLAST, choose VBLAST scheme,completely research various of existing detection algorithms and compare theirperformances by the PC simulation in VBLAST system. At last, it finds the essential factorsof affecting the system performance to support the basis to the detection schedules for thehybrid system. As the results show that: QR decomposition is an ideal detection algorithmfor the VBLAST system, however, the iteration improves the performance at the cost ofcomputation complexity, and if the first layer detection diversity could be enhanced, theiterative times would be reduced.2. The architectures and the detection principles of STBC coding must be wholly surveyed, onthe basis of ensuring the high date-rate, design and choose how to integrate the STBC toVBLAST system. Adopt the VBLAST decoding algorithm; choose to insert the STBCstructure to first layer of the VBLAST architecture referring the QR decompositionalgorithm.3. To use the iteration method in the STBC-VBLAST hybrid system, the dissertation breaks theoriginal thought, the new decoding schedule built on matrix reconstruction is utilized at thereceiver, then the iteration detection algorithm is adopt according to QR decomposition. Thenewly designed schedule causes the BER performance of the system to have an obviousimprovement via increasing the diversity degree. The simulation results in new decoding schedule indicate that: the performance of QR algorithm with iteration has lessthan1dB gap compared with the ML algorithm; when the BER gets to10-3, the newalgorithm has an improvement of almost4dB compared with the original ZF-SIC algorithm.Because the fact that the iteration detection algorithm on the basis of QR decomposition canmake full use of the high diversity gain on the highest layer at each iteration step, theadvantage of the new decoding schedule in the hybrid system can be ensured.