基于内插结合MMSE均衡消除OFDM系统相位噪声的算法

Suppression algorithm of phase noises in OFDM system based on interpolation combined with MMSE equalization

针对正交频分复用(orthogonal frequency division multiplexing,OFDM)系统对相位噪声的敏感特性,提出一种基于内插结合最小均方误差(minimum mean square error,MMSE)均衡消除OFDM系统相位噪声的算法,通过在发射端的IFFT之前,对符号进行零子载波的内插,可有效地降低OFDM系统相位噪声造成的子载波间干扰(inter carrier interference,ICI),提高信干比。通过MMSE均衡方式,可消除OFDM系统相位噪声造成的公共相位误差(common phase error,CPE)。仿真结果表明,本算法可以消除CPE引起的整个信号星座的旋转,同时大大降低ICI引起的信号星座点的云状发散,OFDM系统的相位噪声在高斯信道和多径信道下都能够得到有效抑制,且复杂度低、实现简单,具备良好的实用价值。

Aiming at the orthogonal frequency division multiplexing （OFDM） system is sensitive to the phase noise, a suppression algorithm of phase noises in OFDM system based on interpolation combined with MMSE equalization is introduced. Before IFFT in the transmitter, interpolating the zero subcarriers into the symbol may reduce the inter carrier interference （ICI） effectively and improve the signal-to-interference （SIR） ratio. By using the MMSE equalization method, the common phase error （CPE） of the OFDM system caused by the phase noise can be eliminated. The simulation results show that the algorithm can eliminate the rotation of the constellation caused by CPE and suppress the cloud of divergence of the constellation caused by ICI. The phase noise of the OFDM system can be suppressed effectively over Gauss channel and multipath channel, so the proposed algorithm has low complexity and is good in practice.