Research On Principle Of Fountain Code And Its Applications In Wireless Communication System

With the rapid development of the Internet and communication technology,the higher network transmission rate for various voice,image and video is increasingly been demanded.For all kinds of interference,error codes are generated in the transmission of digital signals.As one of the important anti-interference methods,error coding technology has received extensive attention in the field of digital communication technology.In the process of error correcting coding,the redundant information which related to the original data,is added to the raw data at the transmitting terminal by repetition?interleaving?punching?randomization and so on.At the receiving end,the transmission errors are detected and corrected based on the Error-correcting information and Error-correcting Algorithm.The performance of anti-interference in data transmission is enhanced of communication link is ensured by the small redundancy cost.Fountain code,as a new type of low density and linear block code for the last ten years,with the property of rateless,can automatically match the rate of coding at different communication link according to the channel environment,which is especially suitable for broadcast communications and large-scale data distribution.The fountain code has low complexity of encoding and decoding with excellent performance,which attracted extensive attention of scholars at home and abroad.In the existing fountain codes' theory and its applications,firstly,a new fountain code based on Chinese remainder theorem is studied,and the extended Euclidean theorem is used to improve its decoding performance.Then,the modulo arithmetic fountain codes is introduced to Multi-carrier orthogonal frequency division multiplexing wireless communication systems to improve the peak to average ratio and BER performance.Finally,a concatenated coding system based on fountain codes is studied,which is applied to differential frequency hopping wireless communication systems,and a soft input soft output decoding system is designed to enhance the performance of anti partial-band jamming.The main contents and contributions of this dissertation are as follows:(1)Aiming at the intrinsic problems of Chinese Remainder Theorem in fountain decoding process with modular arithmetic,this paper proposes a decoding algorithm based on extended Euclidean theorem.The linear congruence equations are merged in the extended Euclidean decoding algorithm,which avoids the failure of solving the rate factor when the decomposition factors are non-coprime.In the Modular arithmetic fountain encoding process,the original packet is continuously decomposed by the factor,which is randomly selected from the natural number,into the encoded packets consisting of the residues and the factors.When a certain amount of packets are received,it can be achieved to decode successfully.The codec efficiency has been improved as the algorithm has extended the range of the modular arithmetic factor.Through theoretical analysis and numerical simulation,the effectiveness of this decoding algorithm of modular arithmetic fountain code has been proved.(2)Non-continuous orthogonal frequency division multiplexing(NC_OFDM)has large sidelobe power and high peak-to-average power ratio(PAPR).In this paper,an improved algorithm with Fountain coding is proposed,in which the sidelobe interference in NC-OFDM system and high peak to average ratio are both taken into consideration in the joint optimization algorithm under the circumstance of cognitive radio system.Fountain multi-choice sequence algorithm,by the ideal of Fountain coding and sequence mapping,is adopted for sidelobe suppression and PAPR reduction.The simulation results show that the improved algorithm can significantly reduce the band interference to licensed user(LUs)and make the system PAPR less than target PAPR,so as to solve the problem of NC_OFDM signal distortion caused by power amplifier and finally enhance the overall performance of the system effectively.(3)The improved modular arithmetic fountain codes is applied to in multi-carrier systems;the performance is investigated and simulated in an erasure channel environment.The decoding efficiency of improved modulo arithmetic fountain code is higher because each receiving data packet is directly involved in the decoding.Under the same decoding redundancy,compared to the robust soliton fountain codes and Raptor fountain codes,the improve modulo arithmetic packets needs fewer packets and have higher throughput when transmitting a certain number of packets correctly.(4)In order to improve the performance of rejecting partial-band noise jamming,Fountain code is introduced to the differential frequency hopping(DFH)systems as the outer error correcting code in Concatenated coding systems which can be called Fountain code-differential frequency hopping(Fountain-DFH).The improvements against partial-band noise jamming over Additive white Gaussian channel(AWGN)by employing fountain code is investigated.The performance of Fountain-DFH is theoretically analyzed and numerically simulated with jammer state information(JSI)and no JSI.The total frequency of hopping in the simulation is 32,experimental results show that when exact JSI is available,the system with 32 jamming-frequencies,the performance of SJR is improved up to 2 to 2.5 dB compared with the uncoded system when Pb is 10-4;Meanwhile the performance is improved up to 10 to 12 dB when jamming-frequencies is 1.When JSI is unavailable,a hopping training sequence estimation and decoding algorithm is proposed to acquire accurate JSI,which makes Fountain-DFH systems still have robust anti-jamming performance even without JSI.