基于格雷互补序列的OFDM无线激光通信定时同步  

A timing synchronization scheme based on golay complementary sequence for OFDM wireless laser communication

作　　者：陈善杰 程凌浩 吴俊[2] CHEN Shanjie;CHENG Linghao;WU Jun(Institute of Photonics Technology Jinan University,Guangzhou,Gouangdong 511486,China;Naval University of Engineering,Naval University of Engineering,Wuhan,Hubei 430022,China)

机构地区：[1]暨南大学光子技术研究院,广东广州511486 [2]海军工程大学电子工程学院,湖北武汉430022

出　　处：《光电子．激光》2021年第7期768-776,共9页Journal of Optoelectronics·Laser

基　　金：国家自然科学基金(61875246);广州市科技计划项目(201904020032)资助项目。

摘　　要：正交频分复用(OFDM)是一种能够有效对抗频率选择性衰落的通信技术。因此,结合了OFDM技术的无线激光通信技术成为对抗大气湍流影响的一种重要技术。但是OFDM技术容易受到符号定时同步偏移的影响,导致信号的快速傅里叶变换窗口失准而严重降低通信性能。针对基于OFDM的无线激光通信系统的定时同步问题,提出了一种新的定时同步方案。该方案的训练符号由格雷互补序列组成,利用格雷互补序列的自相关特性,将接收到的训练序列与本地序列做相关运算,实现精确稳定的定时同步。结合大气湍流模型,通过实验与仿真的方式验证了本文提出的方案相比于基于伪随机序列和恒包络自相关序列的方案有更好的定时同步性能。尤其是在0-4 dB的低信噪比时,本方案的定时同步偏移均方差小于1个采样点,这也使得本方案在大气弱湍流信道下,相较于对比方案有2-4 dB的性能提升。Orthogonal frequency division multiplexing(OFDM)is a communication technology to effectively combat frequency-selective fading.Therefore,wireless laser communication system with OFDM has become an important technology to combat atomspheric turbulence.However,OFDM is susceptible to the offset of timing synchronization,resulting in the misalignment of fast Fourier transform window for the received signal and degrading the communication performance seriously.For timing synchronization of wireless laser communication systems based on orthogonal frequency division multiplexing,this paper proposes a new scheme.The training symbols of this scheme are composed of Gray complementary sequences.The autocorrelation characteristics of Gray complementary sequences are used to perform correlation operations between the received training sequence and the local sequence to achieve precise and stable timing synchronization.Combined with an atmospheric turbulence model,the proposed scheme shows better timing synchronization performance than schemes based on pseudo-random sequence and constant envelope autocorrelation sequence,which has been verified through numerical simulation and experiments.Especially at a low signal-to-noise ratio of 0-4 dB,the mean square error of the timing synchronization offset of this scheme is shown to be less than 1 sample,which also makes this scheme obtain performance improvement of 2-4 dB over those comparison schemes in a weak atmospheric turbulence channel.

关 键 词：激光通信 定时同步 大气湍流 Golay互补序列对 正交频分复用 

分 类 号：TN929[电子电信—通信与信息系统]