Research On Performance Simulation For Underwater Acoustic OTFS Communication Systems

Orthogonal Time Frequency Space(OTFS)modulation provides great potential for dealing with high Doppler frequency shift in time-varying multipath channels.Its key idea is to convert the fading,time-varying channel into a non-fading,time-independent interaction revealing the underlying geometry of the channel,so that all information symbols experience the same static channel response.Therefore,it can also have good transmission performance in high Doppler environments.In this paper,we devote to researching the performance of underwater acoustic OTFS communications from the perspective of simulation and conducting simulations based on the underwater acoustic statistical channel and the experimental platform Watermark.By comparing with the underwater acoustic Orthogonal Frequency Division Multiplexing(OFDM)communications which is mature and widely used in the underwater acoustic communications,we simulate and analyze the bit error rate(BER)performance of OTFS technology.Specifically,the research contents and achievements of this paper are as follows:In this paper,we introduce and analyze the basic principles of OTFS technology and its modulation system.The innovation of OTFS technology lies in expressing the signal in the delay-Doppler domain,and its channel response captures the geometric characteristics of transmission,which means that the OTFS waveform is optimally coupled with the wireless channel.In addition,by utilizing the Symplectic Finite Fourier Transform between the signal in the delay-Doppler domain and the time-frequency domain,an OTFS modulation scheme can be constructed on the traditional multi-carrier modulation scheme.Therefore,we discuss the feasibility of the OTFS modulation technology in the underwater acoustic communication system through theoretical simulation and platform testing based on a comprehensive understanding of it.Then,the OTFS modulation system is designed and simulated based on the underwater acoustic statistical channel.Based on a detailed introduction to the characteristics of underwater acoustic channels including path loss,Doppler frequency shift and multi-longitudinal transmission,the modeling of the underwater acoustic statistical channel covers a full description of the effects of small-scale and large-scale fading considering the inevitable effects of random channel changes in acoustic propagation.Based on this,we construct the underwater acoustic OTFS communication system and compare it with the Orthogonal Frequency Division Multiplexing(OFDM)system from two main problems of multipath propagation and Doppler frequency deviation,respectively.The simulation results show that the OTFS provides a better BER performance at the receiver in the underwater acoustic communication environment with multipath and Doppler effect.Based on the Watermark(Underwater Acoustic Channel Replay Benchmark)platform,we design and simulate the underwater acoustic OTFS communication system.As a benchmark for physical-layer schemes for underwater acoustic communications,Watermark allows researchers and modem manufacturers to develop,test and compare algorithms for the physical layer under highly realistic and reproducible conditions.The underwater acoustic OTFS communication system was simulated and tested on different types of acoustic channels in the Watermark platform,and its performance is compared with the underwater acoustic OFDM system considering whether the channel information is known at the receiver.The simulation results show that the application of OTFS technology in the underwater acoustic communication system based on the Watermark platform can improve the BER performance of the system with the known channel information.However,the underwater acoustic OFDM communication system has a lower BER performance when the channel information is unknown.Based on this,a further consideration is adding a channel equalizer to the Watermark underwater acoustic communication system and compare the performance of different modulation schemes.Simulation results show that the performance of the two modulation schemes of OTFS and OFDM is roughly equivalent in this case.