Abstract: To combat synchronization errors in cooperative communication，Orthogomal Frequence Digital Multiplexing（OFDM） technique is applied to achieve the full cooperative diversity and full multipath diversity for asynchronous cooperative communications，in which a kind of Space-Frequency（SF） code is used at relay nodes.Although OFDM can combat timing errors，it is very sensitive to Carrier Frequency Offset（CFO）.For cooperative communication，multiple CFO makes frequency compensation difficult if not impossible.By exploiting the structure of the SF code and energy distribution characteristics of Inter-Carrier Interference（ICI），this paper proposes re-ranging the SF code at transmitter and multiple frequency shifts with corresponding FFT at receiver to combat multiple CFO effectively.Based on this，by using Q tap method，it gets a performance to close Minimum Mean Square Error（MMSE） at the cost of lower algorithm complexity.

Key words: cooperative communication, Space-Frequency（SF） code, Carrier Frequency Offset（CFO）, Orthogonal Frequence Digital Multiplexing（OFDM）

摘要： 在协作通信中为了对抗同步误差，可基于OFDM技术在中继节点采用空频码实现协作分集和多径分集。OFDM可以抗定时误差，但对载波频率偏移非常敏感，对于协作通信，多个载波频率偏移的存在使得频率补偿很难实现。利用空频码结构和载波间干扰能量分布特点，提出在发射端调整空频码相对位置，在接收端进行多次频率搬移和相应的FFT变换，能有效对抗多个载波频率偏移。在此基础上采用Q抽头滤波算法，以较低的算法复杂度实现了接近于最小均方误差的性能。

关键词: 协作通信, 空频码, 载波频率偏移, 正交频分复用技术