Abstract: To explore the parameters estimation of OFDM (Orthogonal Frequency Division Multiplexing) signals in cognitive radio systems, the symbol duration blind estimation of OFDM signals was achieved through the cycle spectrum. Firstly, the cyclostationarity of the OFDM signals with cyclic prefix and rectangular pulse shape was demonstrated. Then based on the cycle spectrum of single-carrier signal and the orthogonality of OFDM subcarriers, the cycle spectrum expressions of OFDM signals were derived on the condition of no noise and low SNR. Finally, the computer simulation results of both the continuous signals and discrete signals are the same, which can estimate the symbol duration of OFDM signals blindly with low SNR through the cycle spectrum.

Key words: cyclic spectrum, cognitive radio, blind signal processing, OFDM(Orthogonal Frequency Division Multiplexing), parameters estimation

摘要： 针对认知无线电系统中正交频分复用(OFDM)信号参数估计这一重要问题,利用OFDM信号的循环谱实现了符号周期的盲估计。首先证明了加循环前缀矩形脉冲成型的OFDM信号具有循环平稳性,然后分别在无噪声和低信噪比条件下,以单载波信号的循环谱为基础,利用OFDM信号各子载波的正交性,从理论上推导出了OFDM信号的循环谱表达式。最后通过对连续信号和离散信号进行仿真,得到了相同的循环谱图,并且在低信噪比条件下,利用循环谱实现了OFDM信号符号周期的盲估计。

关键词: 循环谱, 认知无线电, 盲信号处理, 正交频分复用, 参数估计