Multi-user Coding And Decoding Of Digital Fountain Code And Application In UAV Data Link

Digital fountain code is a kind of erasure codes which is rateless and has been emerging in recent years.According to a probability distribution,it can create encoding symbols with arbitrary numbers independently.Digital fountain code has the advantages of no rate,requiring less feedback resources and adaptive channel state,so it has great advantages in the erasure channel.With the further research on the coding and decoding of digital fountain codes,application in the wireless channel has become one of the hot topics in the research of fountain codes and it is more simply for digital fountain codes to code and decode.Application of digital fountain code to wireless channel also has the advantage,and the code is simple.In this paper,we mainly study the coding method of digital fountain code,which mainly aims at typical broadcast channel and multiple access channel。In addition,the fountain multiuser code is applied to the UAV data link system.The main work of this paper is as follows:(1)At the base of analysis of multiuser bit likelihood ratio calculation and wireless channel characteristics of BP decoding,this paper proposes a likelihood ratio iterative update detection algorithm.Simulation results show that the algorithm can effectively improve the correct probability.Further,this paper put forward a method to reduce the complexity of the likelihood ratio iterative update detection algorithm.The analysis and simulation show that the method could obviously reduce the number of calculating the natural logarithm.With the increase of the number of users,the natural logarithm calculation can be reduced three orders of magnitude.(2)According to the characteristics of multi access channel,this paper analysis the method of using the multiuser decoding in multiple access channel.Simulation results show that the algorithm can make the multiuser decoding performance infinite approach to the single user with the signal to noise ratio gradually increased.Besides,we put forward the concept of digital fountain multi access(DFMA).Comparing the digital fountain multiple access transmission with CDMA,the simulation results show that the fountain has a great advantage in system overhead for the multiple access.(3)Based on the above multiuser decoding algorithm of the digital fountain codes,the digital fountain codes are applied to unmanned aerial vehicle uplink control link.With the control link,the ground console can simultaneously control three UAVs.The transmission scheme of the control link is mainly the single carrier frequency domain equalization scheme.At the sending end,this paper has completed including the simulation of coding,modulation and baseband shaping.At the meantime,the receiver includes the matching filter,frame synchronization,channel estimation,channel frequency domain equalization and demodulation and decoding module.This paper has simulated all above modular.The simulation results show that the digital fountain code in UAV uplink control has a good performance in the link,and the uplink control link can realize the control of multiple UAVS.