Optimized LDPC (Low Density Parity Check) code degree distribution joint search method based on OOK (On-Off Keying) modulation in asymmetric channel

Abstract

The invention discloses an optimized LDPC (Low Density Parity Check) code degree distribution joint search method based on OOK (On-Off Keying) modulation in an asymmetric channel. According to the method, density distribution of an LDPC degree distribution initial variable message space is calculated according to a precise photoelectric conversion module of a photodiode under OOK modulation, and iterative density evolution of LDPC degree distribution is performed, so that the coding and decoding performance of an LDPC code in the channel can be evaluated more accurately; a joint evolution updating method is adopted, a genetic evolution algorithm, a differential evolution algorithm, a particle swarm evolution algorithm and a simulated annealing algorithm are applied to perform optimization search, the weight of each algorithm is adjusted from the aspects of the population size and the number of iterative updating times through considering weight matching of each algorithm and performing operations of disorganizing the population and inserting excellent individuals at regular intervals, global advantages of joint search can be played, limitations of single algorithm are avoided, and the search efficiency is improved. The global performance and the robustness of the search algorithm are enhanced, and the search space is restricted, so that the search is enabled to be performed effectively.

Description

technical field [0001] The present invention relates to the technical field of optical communication, in particular to the optimization of LDPC code degree distribution in a free-space optical communication system using a photodiode (PIN) as a photodetector OOK (On-Off Keying, binary on-off keying, referred to as OOK) modulation The scheme is specifically a joint search method for optimizing LDPC code degree distribution under an asymmetric channel based on OOK modulation. Background technique [0002] As a new communication method, Free Space Optical (FSO) communication has the characteristics of high bandwidth, high speed, flexibility and economy. In the free space optical communication system, due to the existence of unfavorable factors such as light attenuation caused by the absorption and scattering effects of various gas molecules and aerosol particles in the atmosphere, and light intensity fluctuations caused by atmospheric turbulence, the channel conditions deteriora...

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