Research On Spinal Codes With Low-Complexity In Free-Space Optical Communication

Free space optical communication technology is a wireless communication technology that uses laser as a signal carrier and transmits in the atmosphere.It has the advantages of no spectrum limitation,high transmission rate,strong directivity and good confidentiality,and has received extensive attention and research.However,when laser is transmitted in the atmosphere,it is easily affected by absorption,scattering,turbulence and other factors,resulting in the phenomenon of light intensity flicker and waveform distortion.Channel coding technology can effectively suppress the influence of atmospheric turbulence on laser signals,but fixed-rate coding schemes cannot adapt to time-varying atmospheric channel.As a new type of rateless coding scheme,Spinal codes can adapt to dynamically changing atmospheric channels and have great research value and application advantages in free space optical communication.However,the disadvantage is that the decoding complexity is high,which affects the overall performance.Based on this,this paper studies the low-complexity implementation scheme of Spinal codes in free-space optical communication.In this paper,the domestic and foreign research status of free space optical communication technology and channel coding technology is firstly introduced,and expounds the research progress of Spinal codes at home and abroad.Then,the atmospheric attenuation effect and atmospheric turbulence effect that affect the laser signal in the atmospheric channel are analyzed,and the lognormal distribution model and double gamma model that approximate the characteristics of atmospheric turbulence are given.Then,the coding and decoding principles,decoding algorithms and related characteristics of Spinal codes are studied and analyzed in detail.Aiming at the problems of high decoding complexity and unequal error protection of Spinal codes in free space optical communication,this paper proposes a concatenation scheme of segmented CRC(Cyclic Redundancy Check),BCH(Bose-ChaudhuriHocquenghem)codes and Spinal codes,which terminates decoding in advance through segmented CRC check process,reduce the amount of decoding calculation of the Spinal code,and reduce the decoding complexity;and perform error correction protection on the error-prone tail information of the Spinal code by cascading the BCH code at the tail.Afterwards,the simulation analysis was carried out under atmospheric channels with different turbulence intensities.The results showed that under the influence of weak turbulence,low signal-to-noise ratio and medium-strong turbulence,the scheme greatly reduced the free space while ensuring the bit error rate and rate performance.The decoding complexity of Spinal codes in optical communication provides a solution for the efficient application of Spinal codes in free space optical communication.The traditional Spinal code transmission scheme is easy to cause continuous burst errors in turbulent channels,and it needs to transmit additional coding symbols to successfully decode,which increases the decoding complexity.To solve this problem,this paper proposes a Spinal code interleaving transmission scheme with a tail-biting structure.By interleaving the encoded symbols of multiple transmission channels of the Spinal code before transmission,the burst error correction capability of the Spinal code is improved,and the transmission scheme uses The Spinal code is improved to a tail-biting structure,which reduces the lower bound of the error probability of the Spinal code.The simulation results under different code lengths and turbulence intensities show that the scheme has good coding gain,improves the rate performance of the Spinal code,and reduces the decoding complexity.