摘要
海水信道对光的吸收和散射造成信号衰减,海水湍流造成信号幅度起伏变化,两者都会降低水下无线光通信 (UWOC) 系统误码率 (BER) 性能。将两个信道特性对信号性能的影响综合考虑,提出了一种将传输距离和湍流概率密度函数等效为系统信噪比 (SNR) 和湍流噪声的方法,然后将信号衰减和湍流噪声同时作用在信号波形中,建立水下复合信道信号传输模型。依据实验系统参数,模拟复合信道下高斯最小频移键控 (GMSK) 调制的信号传输波形,采用一比特差分解调算法,对比解调波形与原始波形,分析复合信道对系统误码率性能的影响关系。模拟实验结果显示,与开关键控调制(OOK)、脉冲位置调制 (PPM) 相比,仅在海水衰减系数为0.151 m^(-1)的衰减信道下,GMSK 系统分别可获得4 .8、 3.3 dB的信噪比增益。在复合信道下,GMSK 调制性能明显优于 OOK 调制和 PPM 调制,当海水衰减系数为0.151 m^(-1)、湍流对数强度方差小于 0.16 时,GMSK 调制系统无误码率极限,系统误码率由信道的衰减、湍流特性和高斯噪声共同决定,GMSK 调制相比于 PPM 调制获得4.35 dB的信噪比增益;当湍流对数强度方差大于 0.16 时,系统存在误码率极限,极限值由湍流对数强度方差决定,且随着湍流对数强度方差的增加,系统极限误码率非线性递增。
The absorption and scattering of light in seawater channel cause signal attenuation, and the turbulence of seawater causes signal amplitude fluctuation, both of which will reduce the bit error rate(BER) performance of underwater wireless optical communication(UWOC) system. The effects of the two channel characteristics on the signal performance were considered comprehensively, and a method was proposed to equate the transmission distance and turbulence probability density function to the system signal-to-noise ratio(SNR) and turbulence noise, and then the signal attenuation and turbulence noise were combined into the signal waveform to establish the underwater composite channel signal transmission model. According to the experimental system parameters,the signal transmission waveforms of Gaussian minimum frequency shift keying(GMSK) modulation under composite channel were simulated, and the one-bit difference demodulation algorithm was used to compare the demodulated waveforms with the original waveform, and the influence relationships of composite channel on the system BER performance was analyzed. The simulation experiment results show that, compared with on-off keying modulation(OOK), pulse position modulation(PPM), GMSK system can obtain the SNR gain of 3.3 dB,4.8 dB respectively only in the attenuation channel with seawater attenuation coefficient of 0.151 m^(-1). Under the composite channel, GMSK modulation performance is superior to OOK modulation and PPM modulation. When the water attenuation coefficient is 0.151 m^(-1), and turbulence intensity variance is smaller than 0.16, GMSK modulation system has no error rate limit, the system BER is decided by signal attenuation and turbulence noise and Gaussian noise together, GMSK modulation achieves SNR gain of 4.35 dB compared with PPM modulation.Furthermore, turbulence intensity variance is greater than 0.16, system BER arrives limit, which value is determined by the turbulence intensity, and the limit value of BER increases nonlinearly with the increase of turbulence intensity.
作者
杨祎
刘妍
王艺龙
张建磊
杨方明
Yang Yi;Liu Yan;Wang Yilong;Zhang Jianlei;Yang Fangming(School of Electronic Engineering,Xi'an University of Posts&Telecommunications,Xi'an 710121,China)
出处
《红外与激光工程》
EI
CSCD
北大核心
2022年第6期400-410,共11页
Infrared and Laser Engineering
基金
国家自然科学基金(61805199)
陕西省技术创新引导专项基金(2020 TG-001)
水下信息与控制国家重点实验室基金(JCKY2020207 CD02)
陕西省微波光子与光通信创新团队(2021TD-09)
2020年西安邮电大学研究生创新基金(CXJJLY202053)。
关键词
水下无线光通信
复合信道
GMSK调制
湍流对数强度方差
误码率
underwater wireless optical communication
composite channel
GMSK modulation
turbulence logarithmic intensity variance
bit error rate
