Research On Fountain Codes Technology In Wireless Communication

With the development of communication technology,wireless communication has become the main communication method of modern communication,and the quality of wireless communication channel is the main factor affecting information transmission.In order to ensure the reliability of the communication system,automatic retransmission request(ARQ)and forward error correction(FEC)are commonly used for error control.The traditional error correction code is fixed bit rate and cannot adapt to the variable channel.Fountain code is an emerging forward error correction coding method.As a rateless code,fountain code can be applied to various variable channels,which reduces the transmission delay without the low complexity of feedback and coding.Therefore,fountain code has important research value and significance in wireless communication systems with high reliability and low latency.First of all,this paper gives a brief overview of the rateless code and the erasure code.Then the three fountain codes of LT code,Raptor code and BATS code are introduced in detail.The advantages and disadvantages and applicable scenarios are analyzed by describing their coding and decoding process and degree distribution function.Through simulation,the performance of the three fountain codes in the deleted channel and the parameters affecting the performance of the compiled code are analyzed.Secondly,for the security of fountain code transmission in the case that the eavesdropping channel environment is better than the legal channel,by analyzing the parameter difference between the legal channel and the eavesdropping channel,this paper proposes a double artificial noise anti-eavesdropping model based on two-way communication.The design principle of the model is that the receiver transmits a random sequence code to the sender.Due to the environmental difference between the eavesdropping channel and the legal channel,the content of the code sequence that the sender and the eavesdropper can correctly receive also differs,and the sender receives the received code.The portion of the code sequence that selects the correct transmission is superimposed and transmitted with the encoded codeword.Due to the presence of artificial noise and channel noise,the eavesdropper cannot obtain the complete decoding of the stolen information by obtaining all the code sequence information used by the sender.By simulating the application performance of the LT code,Raptor code and BATS code on the model,it can be seen that the anti-eavesdropping model can increase the error rate of the eavesdropping party and ensure the eavesdropping under the premise of ensuring the error rate of the receiver.Finally,since the performance of the original sliding window fountain code is closely related to the overlap size of the sliding window,the more overlapping the adjacent windows,the higher the reliability and the larger the delay.The information of the overlapping part is successfully decoded in the previous round.It will also participate in the encoding of the next window,and there is a problem of wasted channel resources.In this paper,the adaptive sliding window fountain code is proposed.By using the condition of the feedback channel in the two-way communication,the successful or unsuccessful packet number is feedback-decoded,and the adaptive sliding window size is used to effectively improve the throughput rate of the system.At the same time,the maximum information packet of the previous window that has not been successfully decoded is superimposed in the next window and transmitted directly,which increases the decoding success rate of the previous window information.Although there is feedback communication,the feedback information is only the original packet number.When the length of the information in the source packet is long,the delay caused by the feedback is negligible.