Abstract: When used for cognitive radios, the traditional Orthogonal Frequency Division Multiplexing（OFDM） technology with its drawback of the spectral leakage will not only cause interference between neighboring zone but also reduce the primary user signal detection performance. This paper proposes a multi-band spectral detection scheme based on Modified Discrete Fourier Transform（MDFT） modulated filter bank. The detection probability expression of the cognitive radio system under MDFT modulated filter bank structure is derived. Theoretical analysis and simulation results show that the CR system based on MDFT filter bank has higher stop-band attenuation than the system based on OFDM with using rectangular window function as prototype filter. And with the pedestrian channel of 3GPP TS 25.104 protocol standards, especially at lower SNR, the spectrum sensing performance of the CR system based on MDFT filter bank structure is significantly improved compared to the system based on OFDM.

Key words: modified discrete Fourier transform filter bank, spectrum sensing, cognitive radio, orthogonal frequency division multiplexing

摘要： 针对认知无线电系统采用传统正交频分复用（OFDM）技术时，其高频谱泄露带来的邻带间干扰及造成的主用户信号检测性能下降等问题，提出了一种基于改进离散傅里叶变换（MDFT）调制滤波器组的认知无线电（CR）多用户接入频谱检测方案，并推导了CR系统在应用MDFT滤波器组条件下检测概率表达式。理论推导及不同参数下仿真结果表明，与基于OFDM的CR系统相比，MDFT结构的系统比以矩形窗函数为原型滤波器的OFDM系统带外有更高阻带衰减；在较低信噪比情况下，基于3GPP TS 25.104协议标准的多径步行信道采用MDFT滤波器组结构的CR系统频谱感知性能相比于采用OFDM调制方式有了明显提升。

关键词: 改进离散傅里叶变换波器组, 频谱感知, 认知无线电, 正交频分复用