基于双模turbo码的自由空间光通信系统特性分析

Analysis of Free Space Optics System Based on Twofold Turbo Code

在自由空间光通信(FSO)系统中,大气信道的信噪比(SNR)特性对系统的通信性能影响很大,提出了双模turbo码的编码方案.从研究大气对自由空间光通信系统的影响出发,在分析了大气信道特性后建立了大气信道信噪比和能见度的关系,详细阐述了双模turbo码的编码、译码原理.应用建立的大气信道的信噪比关系,仿真分析了大气信道的信噪比和大气能见度的关系和两种编码条件下自由空间光通信系统的误码率(BER).结果表明,对于一个实用的无线光通信系统,在要求系统的误码率低于10-5时,基于双模turbo码的系统所要求的信道信噪比比基于普通turbo码的系统的要求低1 dB.因此在相同的信噪比条件下,相对于普通turbo码,双模turbo码能有效降低系统的误码率.

For the free space optics （FSO） communication system, the atmospheric channel＇s signal-noise-rate （SNR） is a key factor, and the FSO system based on twofold turbo code is proposed. First, the atmospheric influence on FSO system and the character of atmospheric channel are analyzed, the SNR of atmospheric channel versus the weather visibility is deduced, and the coding and decoding principles of twofold turbo code are analyzed. Applied the function of atmospheric channel＇s SNR, the SNR of atmospheric channel versus the weather visibility and the bit error rate （BER） of FSO system based on twofold turbo code and common turbo code are simulated. The results show that, for an applied optical wireless communication system, under the condition of system＇s BER being below 10^-5, the channel＇s SNR of system based on twofold turbo code is ldB lower than that based on common turbo code. So, for the same channel＇s SNR, the twofold turbo code is more efficient to degrade the system＇s BER than common turbo code.