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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.
In the free space optical communication (FSO) system, the signal-to-noise ratio (SNR) characteristics of the atmospheric channel have a great influence on the communication performance of the system, and a coding scheme of dual-mode turbo codes is proposed. The relationship between signal to noise ratio of atmosphere channel and visibility is established after analyzing the characteristics of atmospheric channel, and the encoding and decoding principle of dual-mode turbo code is elaborated in detail.The relationship between signal to noise of the air channel is established by using the simulation and analysis Atmospheric signal to noise ratio and atmospheric visibility and the two kinds of coding conditions free space optical communication system bit error rate (BER) .The results show that for a practical wireless optical communication system, the system requires low bit error rate At 10-5, the system based on dual-mode turbo codes requires a signal-to-noise ratio of 1 dB lower than that of systems based on normal turbo codes. Therefore, under the same signal-to-noise ratio, Modular turbo code can effectively reduce the system’s bit error rate.