基于四进制频移键控调制的无线光通信同态滤波技术研究

Research on Homomorphism Filtering Technology of Wireless Optical Communication Based on Four Frequency Shift Keying Modulation

基于无线光通信链路噪声特性,建立了大气信道等效数学模型。针对大气湍流引起的信号起伏,对通过大气信道的四进制频移键控(4FSK)已调信号采用了同态滤波技术去噪,同态系统中线性滤波器设计了零相位数字滤波器。当信源码字长度取500时,同态滤波去噪后的信号通过过零检测进行解调,在光强闪烁指数s2σ=0.1,信噪比10 dB时,误码率达到7×10-4,滤波效果明显优于传统数字滤波器。仿真结果表明,同态滤波能有效地滤除大气信道中的乘性噪声,能够有效地抑制大气湍流,提高光通信可靠性。

Based on noise characteristics of wireless optical communication,atmospheric channel model was founded.Homomorphism filtering technology was applied to four frequency shift keying（4FSK） modulated signal denoising for atmospheric turbulence.Zero-phase digital filter in homomorphism system is desired.When the length of source code was 500 and the signal to noise ratio was 10 dB,the denoising 4FSK signal was demodulated by the zero crossing detection method,and the bit error rate arrived at 7×10-4 with turbulence parameter σ2s=0.1.The simulation results show that homomorphism filtering could reduce multiplicative noise more effectively than the traditional digital filter,and could control atmospheric turbulence to improve relibility of optical communication.