相干光OFDM系统中MMSE信道估计研究

Optimization of channel estimation for coherent optical OFDM systems with MMSE method

信道估计作为相干光正交频分复用(CO-OFDM)的一种关键技术对系统的性能有着十分重要的影响。本文重点对系统信道估计的实现进行了数学分析,搭建起了CO-OFDM系统仿真平台,并在此平台上将提出的最小均方误差(MMSE)及其改进算法应用到CO-OFDM系统中进行信道估计。结果表明,MMSE及其改进算法能够很好地提高CO-OFDM系统的传输性能,在误码率(BER)为10-3时,与最小二乘(LS)算法相比有约2dB的光信噪比(OSNR)增益,且改进型MMSE算法的复杂度要比MMSE算法低2个数量级。

Channel estimation has a very important impact on the performance of the coherent optical orthogonal frequency division multiplexing （OFDM） system. The physical effects of optical channel, such as chromatic dispersion,polarization mode dispersion,can be obtained through the channel estimation at the receiver by transmitting known data at the transmitter, The original signal then can be restored through the equilibrium technology. This paper conducts the mathematical analysis of the realization of channel estimation after presenting the coherent optical OFDM system, and applies minimum mean square error （MMSE） and improved MMSE algorithms on our built coherent optical OFDM system simulation platform to study the performance of our channel estimation algorithms. The results show that the MMSE and improved MMSE algorithms are able to enhance the performance of coherent optical OFDM transmission system, and have 2 dB optical signal-to-noise ratio （OSNR） gain compared with least square （LS） algorithm at the bit error rate （BER） of 10 3. Th complexity of the modified MMSE algorithm is two orders of magnitude lower than that of MMSE algorithm.