Research On Fountain Codes During Wireless Ultraviolet Communication

Fountain codes,also called rate less codes,are probabilistic forward error correction(FEC)erasure codes with many desirable features.Fountain codes were widely used in large data broadcasts,deep space communication and so on.Ultraviolet Communication was a communication mode used 200nm-280nm wavelength ultraviolet light as an information carrier.It has the advantage of all-weather operations,non-line-of-sight(NLOS)communication with a wide field possible and strong anti-interference ability etc.At the same time,with the advancement ofour airspace reform,a variety of low-altitude aircraft were widely used.But the security issues were more and more prominent.This article aims at researching the wireless UV guiding technology of helicopter emergency landing in comp lex environment.The researches in this article include:different communication strategies,LT codes encoding communication scheme and UEP-LT codes.The main work is as follows:(1)Firstly,the research background and significance are introduced in this article.Then the Binary Erasure Channel and the theory of fountain codes are illustrated.(2)In order to improve the efficiency and the reliability of the helicopter guiding in beacon researching and locate landing,an encoding communication scheme based on unequal level coding Luby Transform(LT)code is proposed.Different communication strategies are proposed for different scenarios.The different guiding strategies considering the unequal level coding scheme are designed.The bit error rate of the unequal level coding LT code with different communication strategies is analyzed.The coding scheme and communication strategy are simulated by computer.The simulation results show that the bit error rate of the unequal level protection encoding scheme is significantly reduced and the coding performance is improved over binary erasure channel.The strategies can adapt to different channel environments,and the reliability of communication is improved.(3)In order to provide greater protection for more important bits,a novel approach to provide unequal error protection(UEP)based on the block duplication method and improved EWF(Expanding Window Fountain)codes over erasure channels,named Stepwise UEP-LT(SUEP-LT)codes,is developed and discussed.Block duplication method,EWF and SUEP-LT codes are simulated and compared over binary erasure channel.The experiment results show that,the SUEP-LT codes provide better performance of UEP scheme.Our approach yielded lower bit error rates for the more important bits and lost the least reliability of the whole data.Priority and reliability of the important data are guaranteed.Thus,helicopter emergency landing safety is improved.In summary,the unequal level coding LT codes,SUEP-LT codes and the communication strategies during the helicopter landing guidance could reduce the bit error rate significantly.The coding performance was improved.The strategies can adapt to different channel environments,and the reliability of communication is improved.