Research On Design And Decoding Algorithms Of Spatially-coupled Codes For Optical Communications

In recent years,with the exponential and explosive growth of information,high-speed and large-capacity optical communications have attracted more and more attention and application.Similar to radio communications,optical communications are also divided into wired and wireless.In terms of wired access,optical transport networks are moving towards rates such as 400 Gb/s;in terms of wireless access,traditional radio communications are falling into the dilemma of spectrum shortage,while wireless optical communications are widely concerned because of their large transmission capacity,flexible networking,good security and other advantages.Faced with high-speed and large-capacity optical communications,in order to ensure the reliable transmission of optical links,the industry has been looking for a coding scheme approaching the channel capacity.Spatially-coupled codes are an extension of the existing coding schemes,whose coding idea combines block coding and recursive convolutional coding.The characteristic of asymptotically capacity-achieving makes the spatially-coupled codes a competitive candidate coding scheme for future optical communications.As a kind of spatially-coupled codes,staircase codes have been selected into the optical communication standard because of their excellent performance.This thesis focuses on the design and decoding algorithms of spatially-coupled codes for optical communications,and the main contents are as follows:1.The channel environment of wireless optical communication system is studied and the widely used channel models and modulation techniques are given,then the universal GammaGamma model and OOK and PPM modulations are realized,and the simulation platform of wireless optical communication system is built.2.For the staircase codes,which have been used as the optical communication standard,their decoding algorithms are mainly studied.First,a variety of hard-decision decoding algorithms are summarized and compared in terms of information exchange and complexity.The simulation results illustrate the performance differences between the different algorithms and the performance differences between the staircase codes and the product codes.The staircase codes with the same component codes can achieve better performance than the product codes.In order to further improve the decoding performance of the staircase codes,the soft-decision based sliding-window decoding algorithm is proposed,which can obtain a performance gain of 0.3 dB ? 2dB at the cost of some increase in complexity.Meanwhile,in order to adapt to the change of channel conditions and reduce the complexity of soft-decision decoding,an adaptive soft-decision decoding algorithm is designed.Finally,for the burst erasure scenario,the performance of the product codes are studied,and the application of the staircase codes in the burst erasure scenario is preliminarily analyzed.3.In order to ensure the reliable transmission of wireless optical links,the performances of two kinds of spatially-coupled codes in the wireless optical communication system are studied.First,the performances of the wireless optical communication system with BMST coded OOK and PPM modulations are given.Next,for the wireless optical communications,the braided self-orthogonal codes are designed,and an iterative double sliding-window decoding algorithm is proposed,that is,the braided self-orthogonal codes are decoded using an iterative sliding-window decoding algorithm,and the component self-orthogonal codes also adopts a sliding-window BP algorithm for decoding.This decoding strategy can effectively reduce the decoding delay and decoding complexity.The simulation results show that,in the wireless optical communication system with braided self-orthogonal codes coded and PPM modulation,the braided self-orthogonal codes can well resist the turbulence effect,which will lay a good foundation for the application of braided self-orthogonal codes in the wireless optical communications.