Research On Key Technology Of Adaptive Frequency Hopping Communication System

Frequency hopping communication has been widely used in military communications and other fields because of its good anti-jamming capability.On the one hand,frequency hopping communication uses a set frequency hopping pattern,and the interfered frequency hopping frequency still participates in the communication process,neglects the influence of interference on the communication quality and makes it difficult to cope with the change of the channel.On the other hand,with the deterioration of the electromagnetic environment and the military demand of electronic countermeasures,military communications have imposed higher requirements on the reliability and anti-interference ability of the communications process.In this context,adaptive frequency hopping technology arises at the historic moment.Adaptive frequency hopping is an anti-jamming communication technology developed on the basis of frequency hopping technology.Its core is the channel estimation unit,which is used to realize the real-time estimation of the channel interference state and the signal to noise ratio,and adaptively adjusts the frequency point of the transceiver according to the channel interference estimation results,thus avoiding the interference in an active manner.According to the estimation results of signal to noise ratio,the transmitting power of the transmitter is adjusted adaptively,and the concealment performance of the system is improved on the basis of guaranteeing the basic communication requirements.This paper focuses on the key technologies of adaptive frequency hopping,and conducts research from both frequency adaptive and power adaptive.Firstly,the technical background,development process and research status of frequency hopping and adaptive frequency hopping are introduced.Then the basic principle of frequency hopping,and the key technologies of pseudorandom code generator,frequency synthesizer and frequency hopping synchronization are introduced,and the simulation research is carried out to lay the foundation for the research of adaptive frequency hopping technique.Secondly,the core of adaptive frequency hopping,channel estimation,is studied in detail,mainly from two aspects: frequency adaptation and power adaptation.For frequency adaptation,based on whether there is interference in frequency hopping points,the frequency points are divided into available frequency points and unusable frequency points.The energy detection algorithm in cognitive radio is used to complete the real-time evaluation of the frequency hopping points,and the interference frequency points and the non-interfence frequency points are correctly distinguished.The non-interfence frequency points constitute a frequency hopping working set to complete the frequency hopping communication process.In view of the shortcomings of many filters and difficult design in general energy detection,a multi-channel binding energy detection algorithm is proposed.A channel classification algorithm based on neural network is proposed to deal with the disadvantage of poor channel classification ability under low signal-to-noise ratio.For power adaptation,an estimation algorithm combining subspace decomposition and M2M4 algorithm is used to achieve real-time estimation of the SNR in the frequency hopping operation range,and the Kalman filter is used to achieve tracking of channel changes and make the power adjustment process more efficient.For power adaptation,subspace decomposition and M2M4 algorithm are combined to achieve real-time estimation of SNR in FH range;the use of kalman filter realizes the tracking of the channel changes,so as to realize the adaptive power.Finally,we study the adaptive frequency hopping synchronization.The common method of frequency hopping synchronization is briefly introduced.By comprehensive analysis of its advantages and disadvantages,the frequency hopping synchronization technology based on TOD is selected to achieve the synchronization of frequency hopping patterns in adaptive frequency hopping communication.To further improve the system's anti-jamming performance,Turbo codec was added to build a complete adaptive frequency hopping communication system simulation model.The simulation results verify the correctness of the adaptive frequency hopping system designed in this paper.