Research On The Application Of Polar Codes In Optical Communication

There has been much recent interest in the subject of polar codes.One of the principal concerns of such theory is to design the good polar codes in the digital communication system.Polar codes can achieve the capacity of binary symmetric channel with low encoding and decoding complexity.In this context,much work involved in these aspects has made much progress.Unfortunately,most of the researches put the point to AWGN channel.Polar codes are applied to the optical wireless communication channel and we analyze the performance of polar codes on optical communication channels in this dissertation.Optical wireless communication,namely free space optical communication,has widely promising applications compared with traditional microwave and RF communication.To begin with,this dissertation gives a brief review of the characteristics of channel coding system in free space optical communication.In addition,the modulation method and the channel coding pattern used in its channel coding system are analyzed.What's more,it presents the methods and techniques used in the optical communication channel and then we analyze the factors that affect the bit error performance of polar codes.This paper is mainly concerned with the design and implementation of various polar codes in the optical channel model.The main contributions in this dissertation is organized as follows:?1?In order to study the application performance of polar codes in atmospheric optical communication,this paper analyzes and abstracts the factors that affect the transmission performance.By studying the atmospheric fading and atmospheric turbulence,channel model is set up for free space atmospheric optical communication under weak turbulence.The multiplicative fading factor of the channel is a random variable that follows the lognormal distribution,in which the additive interference is additive white gaussian noise.?2?The general modulation and demodulation methods are introduced.A soft information extraction method is proposed to reduce the computational complexity in the PPM modulation mode.The main decoding algorithms are introduced in detail.It is the Monte Carlo algorithm that constructs polar codes.?3?According to different weak turbulence intensity on channel model,different polar codes are constructed via C++programming language.To verify the feasibility and effectiveness of the polar code in the optical communication channel,simulations are depicted for different channel parameters and compared with the the existing LDPC in the atmospheric optical communication system.The simulation results of this dissertation show that polar codes can be applied to the atmospheric optical communication system,and under certain condition,the performance of polar codes is superior to the LDPC code under the same simulation condition.When the bit error rate is between 10^-4 and 10^-5,it shows that polar codes can be a good candidate for free space optical communication channels.