无线激光通信中差错控制实验研究

Experimental research on the error control of wireless laser communication

微波通信灵活方便,光纤通信码速率高,无线激光通信兼具微波和光纤通信的优势,但受大气环境的影响不容忽视,差错控制是克服无线激光通信环境影响的一个有效方法。常见的纠错码有RS码、Turbo码和Ldpc码,分别将RS(15,9)码、RS(30,10)码,码长为128码率为1/2的LDPC码、交织长度为64码率为1/3的Turbo码引入无线激光通信系统中,按照设计的实验方案,进行一年多时间的实际测量,对几种前向纠错码的性能进行了比较,实验结果表明:RS(30,10)码纠错能力最强,Turbo码纠错性能稍逊于RS(30,10)码。RS(15,9)码与码长为128,码率1/2的LDPC码的纠错性能相差不大。在不同的雨天环境中,通过采用前向纠错码,可以将误码率从10-4降低到10-6以下;在雪天,可以将误码率从10-3降低到10-5以下;在大雾条件下,可以将误码率从10-3降低到10-5以下;在一般晴好天气下,可以使误码率降低到10-9以下。

Microwave communication has the advantage of flexibility and convenience, optical fibre communication has the advantage of high bit rate. Wireless laser communication has the advantages of both microwave communication and optical fibre communication, but the influence of atmosphere should not be ignored, error control is an effec- tive method to overcome the effect of atmosphere environment in wireless laser communication. The common error correcting codes are RS code, Turbo code and LDPC code. We employed the RS（15,9）code,RS（30,10）code, LDPC code with 128 code length and 1/2 code rate, Turbo code with 64 interleave lencth and 1/3 code rate separately. We did actual measurements for one year to comparing the performance of three forward error codes. The results indicate that RS（30,10） code is the optimum code, Turbo code is the next best code, RS（15,9） and Turbo code have the same performance. After adopting forward error correction the BER can be reduced from 10^-4 to 10^-6 on different rain conditions, the BER can be reduced from 10^-3 to 10^-5 on different snow conditions, the BER can be reduced from 10^-3 to 10^-5 on thick fog condition, and under sunny weather, the BER can be reduced to 10^-9.