Performance of Systematic Distance-4 Codes in Free-Space Optical Communication System

摘要

In this paper, we reconfigured the SD-4 code with both: long and very long code lengths. Firstly, we generated SD-4 code with 15 codeword length that implies SD-4 code 3,900 lengths, secondly, we extended SD-4 code to 32,768 which is very long code length . Our model is based on SD-4 code as an encoding/decoding block cascaded by multiple pulse-position modulations (Q-PPM) in FSO communication environment. Such model performance is evaluated by lognormal atmospheric turbulent fading channels. Furthermore, coding gains are compared with different code lengths and Q-PPM modulations to demonstrate such codes ability of coding with pulse position modulation (Q-PPM). The optimal obtained raw code gain is equal to 0.56 dB for SD-4 at code length (4096) which analyzed with BPPM regarding the other related codewords (channel throughput is not considered). Meanwhile the real code gain results have been obtained and equal to 3.87 dB at code length (32768) for such channel(channel throughput is considered). Tto demonstrate the SD-4 code ability to be coded with Q-PPM, we analyzed such code utilizing 4PPM and 8PPM. Also, we compared our results with existing results for other techniques namely : Hamming, Reed-Solomon, and Bose- Chaudhuri-Hocquenghem.