Research And Verification Of Single Carrier Adaptive Transmission In Sea Clutter Channel

Maritime communication is one of the hot research directions in the field of wireless communication in recent years.Comparing with terrestrial wireless communication,the marine space environment is complicated and changeable,where the waves fluctuate with the change of wind and the air and the steam distribution are not uniform.Besides,the conductivity and permittivity of sea water have time-varying characteristics.All these factors above lead to the rapid changes in the propagation environment of electromagnetic waves on the ocean surface.At the same time,the reflection,diffraction and refraction phenomena of electromagnetic wave signals in the transmission process are also more complicated than terrestrial wireless communication scenarios.For this reason,it is imperative to research a high-speed adaptive transmission system that could adapt to the harsh electromagnetic environment of the sea.The main research includes the following three aspects.First and foremost,introduce the research status of the maritime communication system at home and abroad,the research status of the single-carrier frequency division multiple access technology for maritime communication and its application advantages in the uplink transmission system in detail.Systematically summarized the research status of key uplink transmission technologies such as time synchronization,frequency synchronization,channel estimation and frequency domain equalization.After that,discuss the functional requirements of the single-carrier system,determine the four transmission rates and the top-level structure of the transmission waveform.Finally,analyze three important channel parameters in detail: propagation attenuation,Doppler frequency shift,and multi-path delay effects on single-carrier transmission.In the next part,for the uplink transmission of maritime communication,give the design process and detailed design scheme of the physical layer baseband in the singlecarrier system.Specifically,the baseband includes modulation,subcarrier mapping,inverse Fourier transform and framing in the transmitter,and time synchronization,frequency synchronization,channel estimation,frequency domain equalization and soft demodulation in the receiver.The algorithm principles and design basis of all these units in the baseband are given.Moreover,the computer performance simulation of the designed single-carrier adaptive transmission system is carried out,which gives the simulation results of the propagation attenuation law,frequency synchronization performance and anti-multipath performance of the single-carrier transmission system.The floating-point simulation verification is completed.Last but not least,the hardware implementation and experimental verification of the key modules of the single-carrier adaptive transmission system are completed.Give the detailed implementation scheme and hardware resource consumption for the subcarrier mapping and framing of the transmitter,and the channel estimation and frequency domain equalization of the receiver.At last,give the results of the laboratory desktop test and microwave anechoic chamber test under the four rate modes.Comparing the experimental results with the theoretical simulation,there is 2?3 d B difference in performance,which verifies the feasibility of the design scheme.The single-carrier adaptive transmission waveform and verification scheme can be used in engineering applications,and have certain reference value for the design of highspeed,long-distance,and limited transmit power maritime wireless communication systems.