Research On Joint Coded And Modulation Technology In Underwater Acoustic Communication

Underwater acoustic communication has the characteristics of narrow bandwidth,strong noise,and strong signal time-variability,which puts forward new requirements for channel coding and modulation technology.To achieve a more robust and efficient communication,the discussion of channel coding and modulation under the situation of underwater acoustic channel.At the same time,the rapid development of channel coding and modulation technology in wireless communication has produced many excellent channel coding and modulation schemes.While in underwater communication,researches in this filed are still insufficient,and the research on joint coded and modulation technology is also preliminary.Therefore,this research can provide reference for the selection of underwater acoustic communication channel coding,decoding and modulation technology,and will help us to save the signal-to-noise ratio and improve the quality of underwater acoustic communication.In order to screen out a channel coding scheme which meet the demand of short code length in underwater acoustic communication,this paper selects and studies some channel coding scheme that possess a superior performance in radio communication.This paper applies differential and high-order differential modulation to resist the doppler shift which caused by the relative motion of underwater target,besides,the Multi-Symbol Differential Detection(MSDD)algorithm is adopted to overcome the SNR lose caused by the using of differential modulation.When the relative accelerated motion between transmitter and receiver exist,the loss of correlation peak magnitude will occur,thus a new receiver structure that overcomes this problem by adaptively replacing the reference signal is proposed.In addition,this paper also investigates the high-spectrum Effective modulation technology,such as high-order PSK,CPM improve the spectral efficiency.For the problem of strong noise,this paper appropriately increases the complexity of the receiving end in exchange for performance gains,so the joint coded modulation technology is adopted to have a joint design of coding and modulation.Theoretical simulation shows that when the length of the information sequence is about 100 bits,the convolutional code can be selected as the channel coding method,and when the sequence is longer,the LDPC code and Polar code can be selected as the channel coding method;high-level soft demodulation technology and CPM modulation has a significant effect on improving the spectrum efficiency of the system;in the concatenated code simulation,the cascade of CRC and Polar codes can effectively improve the performance of Polar codes under short code lengths,while the cascade of RS codes and convolutional codes can It has performance advantages in resisting sudden errors,especially contiguous errors;differential and high-order differential can effectively deal with Doppler expansion,and the loss of signal-to-noise ratio caused by differential can be compensated by MSDD algorithm.Theoretical analysis and lake test data show BICM-ID,DDPSK and D^3PSK systems have excellent performance in the presence of Doppler,and can further improve the performance of the differential system through a small number of iterations.This paper studies and simulates the channel coding and decoding technology and modulation technology,provides a reference for the channel coding selection of underwater acoustic communication,and gives an effective modulation method,which can solve the Doppler and Doppler in underwater acoustic communication.The problem of low spectrum efficiency;in addition,several excellent joint coding and modulation schemes given in this article can effectively improve the anti-noise ability of the transmitted codeword in the underwater acoustic channel.