平流层衰落信道下QOTDM系统的盲均衡研究

Blind Equalization Research for the QOTDM System Based on HAPs Fading Channels

提出一种在平流层衰落信道条件下适用于准正交时分复用(QOTDM)系统的盲均衡算法。发送端基于QOTDM基本原理得到频谱白化的发送信号,接收端根据发送信号的特性,用梳状滤波器对接收信号滤波,恢复样点序列。通过改进的恒模算法(MCMA)对样点序列初步均衡,时分分接后再通过阶数很短的MCMA-FSE-DFE方法均衡,可以消除多径衰落带来的符号间干扰。在平流层衰落信道下,该算法可以明显消除QOTDM系统存在的误符号率下界。在相同的信息传输速率,相同的信道条件下,当信道的莱斯因子为10dB、系统的误符号率在10-3左右时,该算法比基于DFT信道估计算法的OFDM系统有3.5dB左右的性能改善。

A blind equalization algorithm for the Quasi-Orthogonal Time Division Multiplexed （QOTDM） system based on high altitude stratospheric platforms （HAPs） fading channel was proposed.At the transmitter,the transmitted signal with white frequency spectrum could be obtained based on the theory of QOTDM,and the receiver could get the sample sequences by filtering the received signal with a comb filter.The sample sequences were firstly equalized blindly by the modified constant modulus algorithm （MCMA）,and the output of the primary equalizer was equalized by MCMA-FSE-DFE methods with very short length of weights.After the equalization,the inter symbol interference （ISI） could be cancelled.It is shown by Monte Carlo simulation that the new scheme can cancel the SER limit of QOTDM system in the HAPs fading channel.Under the same bit rate,and the same channel condition,when the Rice fading factor is 10dB,and SER is 10-3,the signalto-noise ratio of QOTDM is about 3.5dB lower compared with OFDM system,which is based on the DFT channel estimation arithmetic.