Research And Algorithm Realization Of PAPR Restrain In MIMO-OFDM Systems

Multi-input Multi-output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) can increase the system capacity and efficiency, resists the multi-path fading, has high use ratio of frequency spectrum at the same. So it is regarded as a key technology of the fourth generation mobile communication system, and it gets more and more attention.However, MIMO-OFDM system have the shortcoming of high peak to average power ration (PAPR) because the IFFT transform in modulation of the sending symbol sequence, this disadvantage affect the performance of MIMO-OFDM systems seriously. The existing MIMO-OFDM system PAPR algorithm is mostly apply the PAPR algorithm of OFDM system to each antenna directly without taking into account of the character of the MIMO-OFDM system, so that algorithm not only need large quantity of calculation but also increase the amount of sideband information transmission reducing transmission efficiency.In this paper, on the base of the character of MIMO-OFDM system we mostly analyze the PAPR restrain algorithms of MIMO-OFDM system. Then the proof and analysis of the signal that through the orthogonal space-time coding has the same PAPR with its conjugate signal, and the orthogonal space-time code structure has the character of conjugate and symmetry is given firstly. Based on that and a Low-complexity PAPR reduction algorithm for MIMO-OFDM system is proposed. The simulation result shows that this algorithm is better than the present algorithm, it not only reduce computational complexity significantly and reduce the amount of iteration computation but also improved PAPR reduction effect slightly at the same time. So this algorithm can improve performance of the system. In addition, aiming at the SFBC MIMO-OFDM system, we apply the principle of cross-antenna rotation and inversion algorithm in STBC MIMO-OFDM to the SFBC MIMO-OFDM system, propose the sub-carrier rotation optimal and suboptimal algorithm in SFBC MIMO-OFDM system. The simulation result shows that algorithm have better PAPR than original signal.