Research On Sparse Orthogonal Multi-carrier Modem Technology In Underwater Acoustic Communication

Underwater acoustic(UWA)multi-carrier communication technology is the most widely used technology in UWA communication.It has the advantages of high transmission rate,good robustness and long transmission distance.However,UWA communication channel has the characteristics of limited bandwidth,serious multipath effect and Doppler Effect.So multi-carrier communication still faces many challenges in UWA communication.The serve Doppler Effect is the most serious problem in multicarrier communication.In this paper,we design a novel multi-carrier modulation method for UWA communication system and adds appropriate estimation compensation technology to enhance the transmission performance of multicarrier communication system.The new multi-carrier modulation technology designed in this paper uses dictionary matrix instead of IFFT matrix in traditional OFDM system,which increases the sparsity of the transmitted signal,makes it more suitable for underwater acoustic channel and saves spectrum resources.The simulation results show that this method has better BER performance than the traditional orthogonal frequency division multiplexing technology.Compared with the terrestrial wireless channel,the underwater acoustic channel has more serious Doppler Effect which will affect the orthogonality between the sub carriers.In this paper,we use the preamble structure based on the doppler sensitive signal to estimate the expansion factor of the underwater acoustic channel,and make corresponding compensation to improve the performance of the communication system.The simulation results show that adding the compensation technology can improve the reliability of UWA communication system.Besides the simulation experiment,this paper designs a practical UWA communication system based on sound card and data collector,and verifies the feasibility of this method in laboratory pool and campus artificial lake.