Optical communication signal detection for on-off key modulation of opticalcommunication signal across turbulent channels based on SVM
Li Chuyu,Wang Yimin,Xu Zhiyong,Wang Jingyuan,Li Jianhua, Zhao Jiyong
(College of Communication Engineering, Army Engineering University of PLA, Nanjing 210001, China)
Abstract: Free space optical communication performs well in providing fast and stable data transmission, resistance to external interference and strong security. In the process of laser transmission in atmospheric channels, the communication performance is generally affected by atmospheric conditions, and the optical scintillation effect caused by atmospheric turbulence will lead to the deterioration of system link performance. In this paper, the decision method of onoff key modulation signal in free space optical communication under weak atmospheric turbulence channel is studied. Firstly, numerical simulation of real weak turbulence channel is carried out based on lognormal model. In view of the difficulties such as unknown channel conditions and mismatch between model training data and actual situation, data augmentation method is used to train and improve the decision performance of support vector machine. Then the decision ability across turbulent channels is improved. Experimental results preliminarily verify that data augmentation method can improve the effectiveness of SVM decision model in the case of channel mismatch.
Key words : free optical communication; onoff key regulation; channel robustness; support vector machine(SVM)
0 引言
自由空間光通信(Free Space Optical,FSO)具有高速率、高傳輸容量、抗干擾、免頻譜許可、高保密性、通信性價(jià)比相比于光纖高等優(yōu)勢(shì),是一種十分有前途的無(wú)線光通信技術(shù)。然而,在激光通過(guò)大氣信道傳播過(guò)程中,光束和周?chē)髿馕⒘Vg的相互作用產(chǎn)生的大氣吸收和散射等效應(yīng),對(duì)光接收功率產(chǎn)生一定影響。而大氣層中空氣密度的無(wú)規(guī)則起伏,稱為大氣湍流,是影響光信號(hào)質(zhì)量最主要的原因。大氣信道光束經(jīng)大氣湍流作用后,引起光強(qiáng)閃爍和光束相位的隨機(jī)變化,造成接收信號(hào)的誤碼率提高,大大降低了接收信號(hào)的質(zhì)量,最終使FSO系統(tǒng)的性能發(fā)生嚴(yán)重劣化。機(jī)器學(xué)習(xí)在無(wú)線光通信領(lǐng)域的運(yùn)用目前主要集中在無(wú)線光通信中的光性能檢測(cè)、信道均衡與補(bǔ)償、光信號(hào)的測(cè)量和分析方面,它在克服湍流影響中的應(yīng)用已在發(fā)展湍流模型、湍流模擬方法、非線性補(bǔ)償?shù)阮I(lǐng)域取得了進(jìn)展。機(jī)器學(xué)習(xí)方法能夠有效地處理高復(fù)雜度優(yōu)化和高度非線性問(wèn)題,為湍流模型的研究提供了新的思路。