Research On Morse Code Error Correction Algorithm Based On LDPC

Morse code communication using single tone signal transmission has the advantages of light equipment,simple structure,strong signal anti-interference ability,flexible mobility,long communication distance and so on.It is still the guarantee of military communication at present.Units at battalion level and above are routinely equipped with short-wave radio stations with Morse telegraph function.The traditional Morse code relies on manual sending and receiving.With the development of technology,the automatic sending and receiving of traditional Morse code is realized,but the automatic sending and receiving does not have the function of error correction.In order to solve the error code problem caused by noise interference,LDPC coding is applied in the error correction of automatic sending and receiving,and the digital coding of Morse code and LDPC coding and decoding algorithm technology are deeply studied and analyzed,and the communication under the on-off keying mode of Morse code is simulated.The LDPC decoding algorithm is taken as the core,and the error correction function of Morse digital code in communication is realized.The main work of this thesis is as follows:(1)Exploring the characteristics of traditional Morse code in coding and converting it into digital code signal according to coding rules.An improved source encoding method of Morse digital code with equal length is proposed,which avoids the mutual interference between characters when the receiver looks up table and analyzes,and improves the transmission rate of the signal.(2)Studying the classical decoding algorithms of LDPC codes.Normalized min-sum(NMS)algorithm is improved,and the iterative decoding process based on minimum and subminimum values is realized under the layered message mechanism,which improves the convergence speed and accuracy of the decoding process.(3)Referring to the communication process of traditional Morse code,the error correction communication process of Morse digital code is simulated.After the source encoding of Morse digital code is carried out,the corresponding parity bit is obtained by LU encoding algorithm,and the channel encoding sequence is obtained by combining the information bit with the parity bit.Then,through OOK modulation,the signal is transmitted to the receiver through a channel containing Gaussian white noise.The receiver performs nocoherent demodulation and other operations on the signal,and uses LDPC decoding algorithm to correct errors.Finally,compare Morse code table for decoding.(4)According to the characteristics of iterative decoding,the deep neural network is combined with the NMS decoding algorithm.In order to improve the reliability of transmission and the adaptability of decoding algorithm to channel,Morse digital code transmitted by OOK is used as the data set to train and test the NMS decoder under the neural network.The experimental results show that when the bit rate is 1/2 and the SNR is-5dB,the NMS decoder of a neural network in which the same layer of neurons share a multiplicative factor can reduce the character error rate from about 0.3 to about 0.1 with a small number of iterations.In addition,the improved layered NMS decoder can perform better decoding performance at high SNR.In this thesis,the traditional NMS decoding algorithm is improved,and the excellent error correction performance of LDPC is applied to is applied to the communication of Morse code.The error correction function of Morse code automatic receiving is realized and a good effect is achieved.