Research On Detection Algorithm For MIMO-OFDM System

Multiple input multiple output (MIMO) is well known as a great breakthrough in smart antenna techniques of wireless mobile communication areas. It can exponentially improve the system capacity and spectral efficiency. The Orthogonal Frequency Division Multiplexing (OFDM) has the ability to overcome the multi-path interference and frequency selective fading. The MIMO-OFDM system which combined MIMO and OFDM can provide better performance. It is a most promising communication system for the future wireless communication.Generalized MIMO technology is comprised of transmit diversity and spatial multiplexing. The vertical bell laboratories layered space-time (V-BLAST) technology is a typical application of spatial multiplexing, but it can not get the transmit diversity. The proposed space-time coding technology just to make up this shortfall, in which the space-time block code (STBC) is quite practical for its lower decoding complexity at the receiver. This paper mainly researched the application of V-BLAST and STBC in MIMO-OFDM system in detail.Firstly, the research background and significance was described, and then the summary of the development of wireless communication, and the detection technology status of the system receiver and its future development was introduced.Secondly, the wireless communication channel characteristic was introduced, and the V-BLAST system and V-BLAST MIMO-OFDM system ware given and analyzed. Focused on the detection algorithm of V-BLAST MIMO-OFDM, analyzed some typical detection algorithms, and the bit error rate (BER) performance was simulated and compared.Thirdly, the very promising detection algorithm called QRD-M algorithm was studied. Based on the problem of high computational complexity when the QRD-M algorithm obtained the better performance, we proposed two improved detection algorithm, named SQOC algorithm and QMC algorithm, and verified the performance of the two algorithms by computer simulation. The SQOC algorithm used sorted QR decomposition and ordered serial interference cancellation (OSIC) to achieved better trade-off between computational complexity and performance by reducing the branch search space. The QMC algorithm focused on the performance of the first detected signal floor, used different detection algorithm and saved different nodes in different signal floors, therefore improving the effectiveness of the branch search, not only achieved better performance, computational complexity was also decreased.Lastly, the STBC is introduced, based on the Alamouti STBC, the STBC and V-BLAST combined with MIMO-OFDM system is researched, three transmit system models are analyzed and given. The STBC diversity gain and the V-BLAST multiplexing gain are analyzed and compared, and the optimal trade-off curve was given. Then focused on the detection algorithm on the receiver based on the first transmit system model, and proposed a group iterative QR detection algorithm with a lower complexity, and simulation results show that the algorithm obtained an effective combination within spatial diversity and spatial multiplexing.