中文摘要：

与联合空时编码的多输入/多输出的正交频分复用（STBC MIMO？OFDM）系统比较，联合空频编码（SFBC）的MIMO？OFDM系统具有更优的抗多径时变衰弱信道能力，已被TD？LTE制式采用。针对SFBC MIMO？OFDM系统存在峰值平均功率比过高的问题，提出一种低复杂度的子块间空频变换算法。首先在频域上，对所有天线的空频分组码序列进行均等分块，对天线间相应子块进行交叉反向产生候选序列，并从候选序列中选择PAPR最小序列。然后，在时域上对各天线内子块同步进行逐次循环移位，进一步选择最优PAPR序列进行传输。通过结合IFFT特性和SFBC特性分析实现大幅度降低算法复杂度。仿真结果证明在保证SFBC正交性的基础上，算法具备有效性和可靠性。

英文摘要：

Compared with STBC MIO-OFDM system,SFBC MIMO-OFDM system which is adopted by TD-LTE system has better ability to resist damages of multipath time-varying fading channel. Because of the fact that peak-to-average power ratio （PAPR）of SFBC MIMO-OFDM system is too high,an algorithm of space-frequency transformation between sub-blocks with low complexity is proposed. In the frequency domain , equal partitioning into sub-blocks generated from space-frequency block coding （SFBC） sequence of each antenna is conducted. For generation of candidate sequences,inversion cross of the corre-sponding sub-blocks between antennas are performed and PAPR minimal sequence is selected from candidate sequences. In the time domain,successive cyclic shifting of sub-blocks in each antenna are executed synchronously to do further selection of opti-mal PAPR sequence for transmission. With analysis on the characteristics of IFFT and SFBC,the complexity of PAPR algorithm can be further reduced. The simulation results prove that the scheme is valid and reliable in the premise of ensuring the orthogo-nality of SFBC.