Research On Elimination Of Underwater Acoustic Communication Interference Based On Adaptive Filtering

How to reduce the bit error rate of the communication system in underwater acoustic communication is a hot topic for scholars.In this thesis,adaptive filtering algorithms are studied,two adaptive filtering algorithms that have obvious suppression effects on ocean pulses are selected to make theoretical improvements,and then the improved algorithms proposed are applied to the research of interference cancellation in underwater acoustic communication.In view of the fact that Orthogonal Frequency Division Multiplexing(OFDM)technology is relatively mature and has a wide range of applications,it has strong spectrum advantages and can resist some interferences in underwater acoustic communication.It is suitable as a modulation method for underwater acoustic communication.In addition,with the help of the full-duplex communication mode,signals in the same frequency band can be sent and received simultaneously,which greatly improves the efficiency of OFDM underwater acoustic communication.However,there is impulsive noise in the ocean that cannot be ignored,which interferes with underwater acoustic communication.And for the multipath effect in the underwater acoustic channel,it will cause serious Inter Symbol Interference and Inter-Carrier Interference.At the same time,using duplex communication,the receiving end of the transceiver will receive the signal sent by the transmitting end of the transceiver,causing self-interference.These interferences all lead to a high bit error rate of the communication system.Therefore,this thesis adopts the Least Mean P-Norm(LMP)and the Maximum Correntropy Criterion(MCC)adaptive filtering algorithm,which have a better suppression effect on impulse noise.(1)This thesis studies the influence of the step-size factor on the convergence speed and steady-state error of the LMP algorithm.Combined with the improved hyperbolic tangent function,a variable-step LMP algorithm is proposed.This algorithm can generate a larger step size to speed up the convergence speed,and then gradually reduces the step size,so that the steady-state error of the algorithm is gradually reduced.At the same time,the value range of p-norm in the LMP algorithm is studied and analyzed,and the ocean impulse noise is modeled through parameter estimation to determine the value range of p.(2)This thesis uses the variable step size LMP algorithm proposed in this thesis is analyzed under impulse noise.The simulation results show that it can achieve faster convergence speed and lower steady-state error while suppressing impulse noise.After that,the self-interference cancellation of full-duplex communication is carried out.The simulation results show that the variable step size LMP algorithm can eliminate self-interference well.(3)This thesis proposes a variable step size MCC algorithm based on a variable kernel width MCC algorithm.The variable step size MCC algorithm proposed in this thesis is based on the suppression of impulse noise by the Gaussian kernel function and the properties of the Sigmiod function,which can accelerate the convergence speed while maintaining a low steady-state error.(4)The variable step size MCC algorithm proposed in this thesis is used to shorten and equalize the multipath effect existing in underwater acoustic communication.through the equalizer to realize the restriction on the multipath channel,thereby eliminating the inter symbol interference and inter carrier interference caused by the maximum delay extension in the multipath effect that is longer than the guard interval length in OFDM,and reducing the communication the bit error rate of the system improves performance.