中文摘要：

多输入多输出-正交频分复用（MIMO-OFDM）系统固有的较高峰均功率比（PAPR）限制了该技术的发展与应用。为了抑制较高的PAPR值,在传统算法近似梯度投影（AGP）和选择性映射（SLM）的基础上提出了QAS算法,通过建立QPSK调制的SFBC MIMO-OFDM系统模型,仿真了QAS、AGP、SLM算法的PAPR以及误码率（BER）性能,并进一步研究了不同子载波以及不同支路数对QAS算法降低PAPR性能的影响。仿真结果表明,QAS算法与传统算法AGP、SLM相比,可以有效改善MIMO-OFDM系统发射信号的PAPR值,而不破坏系统的BER性能;QAS算法对PAPR的优化性能随着子载波数目（N=32,64,128,256,512,1 024）的增加而下降,随着支路数（M=4,8,16）的增加而提高。

英文摘要：

MIMO-OFDM systems which take full advantage of time, frequency and space di- versity have become a key technology and promising candidate for wireless communications. MI- MO-OFDM systems have an inherent drawback in that the transmitted signals may suffer from a high peak-to-average power ratio （PAPR）, which limit itss development and application. In this paper, a new algorithm is proposed, which is based on the combination of AGP and SLM tech- niques for PAPR reduction in QPSK-modulated SFBC MIMO-OFDM systems. Simulation results demonstrate that the proposed approach achieves a significant reduction in PAPR without sacrifi- cing the BER performance ; The PAPR behavior of the transmitted MIMO-OFDM under QAS in- creases considerably as the value of the number of subcarriers （N=32, 64, 128, 256,512, 1 024） and branches （M=4, 8, 16） increases.