Research On Underwater Narrowband High-speed Electromagnetic Wave Communication Technology

The ocean is rich in material resources,which is a strategic area necessary for the economic and military development of all countries.The communication among platforms such as underwater sensor network,submarine optical cable,underwater robot,AUV and frogman needs higher transmission rate and reliability.The application of electromagnetic wave in underwater has the characteristics of high information rate,strong anti-interference ability and low probability of interception.However,due to the inherent characteristics of the water medium,underwater electromagnetic wave communication is facing some difficulties,so the design of underwater electromagnetic wave communication system is an urgent problem to be solved.In this paper,the mathematical calculation and simulation are studied,which make the underwater electromagnetic wave communication have a reliable theoretical support and lay a foundation for practical engineering application.Based on the Maxwell equations,the propagation parameters of electromagnetic wave in water medium,such as attenuation constant,phase-shift constant,wavelength,phase velocity,are derived,and the propagation mechanism is given.The radiation of the electric dipole and the magnetic dipole is solved.After calculation and simulation,it is found that the magnetic dipole is more suitable for underwater electromagnetic wave communication.It also lays a theoretical foundation for the design of underwater antenna in the following engineering applications.For communication in deep water environment,a direct path propagation model is established.The formula of path loss is derived and verified by the simulation of magnetic dipole antenna.Aiming at the shallow water environment,the surface wave effect in layered media is studied,and the two-layer water air propagation model is established.Combined with simulation and derivation,the path loss is given.It provides a theoretical basis for underwater long-distance electromagnetic wave communication.Based on the direct wave model of deep sea environment,an underwater electromagnetic wave communication system is designed.Based on the analysis of the channel characteristics,the communication parameters are determined,and the performance of different modulation modes in the single carrier system is compared by simulation.An underwater electromagnetic wave communication method based on OFDM is proposed.The simulation results show that the performance is better than that of single carrier system.According to the performance difference of modulation mode and the characteristics of channel response,an optimization method is proposed to allocate subcarriers to different modulation modes.Based on the consideration of frequency band utilization,the reliability performance is greatly improved.The scheme improves the utilization rate of frequency band and further reduces the error rate of the system.It can achieve high-speed underwater short-range communication.