Research On Equalization Technology Of Scattering Frequency-hopping Communication

Troposcatter communication has the advantages of long single-hop span and wide available frequency band,and occupies an important position in military applications because of its anti-interference and invulnerability.At the same time,scattering communication can effectively enhance the bandwidth of short-range satellite communication and alleviate the occupation of satellite transponders,so scattering communication is regarded as one of the best choices to expand the bandwidth of satellite communication and replace multi-hop lineof-sight transmission relay.With the development of network,data-based information transmission needs higher speed,which will cause serious intersymbol interference.Therefore,it is necessary to study the equalization technology in scattering communication.Aiming at the requirements of high-speed data transmission,secrecy and anti-interference in scattering communication system,this topic studies the equalization technology suitable for scattering frequency-hopping communication system,and combines diversity combining technology,frequencyhopping technology and coding technology to design the scattering frequencyhopping communication system scheme.The research contents of this thesis include the following aspects: the characteristics and simulation model of scattering channel,the equalization technology in scattering channel,and the scheme design of scattering frequency-hopping communication system.In this thesis,firstly,the characterristics of scattering channel are studied,Based on the theory of scattering radio wave propagation,the link loss of scattering channel is analyzed,the classical method of scattering link loss prediction is introduced,and the fast fading characteristics and slow fading characteristics of scattering channel are analyzed.Combined with the characteristics of scattering channel,the channel simulation model is selected,and the time domain response and frequency domain response of the channel are obtained through simulation.Secondly,the equalization technology is studied in scattering channel,and the adaptability of time domain equalization and frequency domain equalization algorithm in scattering channel are analyzed,and it is concluded that frequency domain equalization has better adaptability in scattering channel.Furthermore,the problems existing in frequency domain equalization are analyzed,the channel estimation method based on sliding pilot block and DFT is studied,and the problems existing in their application in scattering frequency-hopping system are analyzed.Multipath delay tracking technology is introduced to improve the two algorithms,which improves the information transmission efficiency and adaptability to timevarying channels.Finally,using the improved equalization algorithm,combined with diversity,frequency-hopping and coding technology,the communication scheme of scattering frequency-hopping system is designed.Quadruple spatial diversity and double frequency diversity are used to achieve the purpose of octave diversity.The frequency-hopping pattern combining frequency-hopping and diversity is designed,and the coding and decoding scheme of LDPC code is determined.Combined with various technologies,the scattering frequencyhopping communication system model is built,the process of information transmission and processing is described,and the system parameters are set,including hopping speed,frame length,coding length and code rate.Then,the BER performance of the system is simulated and analyzed,the BER curves of the system under different parameters are compared,and the system performance under different modulation methods,different coding schemes and different hopping speed settings is analyzed.