循环延迟冗余技术(CDD)是OFDM系统中对抗码间串扰的一项重要技术.CDD在发送端采用多天线,不同天线采用不同的相位延迟,从而增加发送端等价的信道频率选择性.首先对CDD技术进行综合评述,然后分析了CDD中的最佳延迟选择,并和CDD技术和经典的Alamouti空时码进行性能比较.仿真结果显示最优延迟下CDD技术能达到更好的性能,并且对天线阵列的数目没有约束.%Cyclic delay diversity(CDD)is a suggested spatial diversity transmission scheme applied in OFDM systems to mitigate inter-symbol interference,by increasing the frequency selectivity of the channel seen at a single antenna receiver.An overview of space frequency-CDD coding(SFC-CDD)is provided and the optimal selection of the time domain cyclic delays is analyzed.Comparison with the well-known Alamouti scheme is presented and the analysis is then extended to muhiple transmit and receive antennas.It is shown that for an SFC-CDD scheme bene-fits from spreading and channel coding that makes it very competitive since it is applicable to any number of tl_ans-mit antennas with no loss in rate.It is shown that full diversity is achieved even without additional coding
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