Research On HF Link Frequency Selection Technology For Large-scale Regional Emergency Communication

Short-wave(3MHz～30MHz)communication is the basic means of national and military telecommunications,which can realize global over-the-horizon communication through ionospheric reflection,and is widely used in large-scale regional emergency communications,mobile communications and other fields.In the case of failure of the satellite communication system,shortwave communication is the main means of realizing emergency communication,and sometimes even the only means.The accuracy of frequency selection is the main factor that restricts the reliability of short-wave emergency communication in large scale area.In view of the difficulties in selecting the frequency of emergency communication and the low accuracy of traditional frequency prediction methods.Based on the ionospheric data detected at present,this thesis optimizes the long-term prediction model based on the ionospheric prediction method in the New Asia Pacific region.Secondly,for the short term of the ionosphere,a strong tracking of Kalman filtering short-term forecasting methods is proposed.Finally,combined with the optimized long-short forecast model,the fusion prediction and verification of short-wave emergency communication frequency in large scale area are carried out.Specific research contents are as follows:1.In view of the regional limitations of a single ionospheric observation station,a long-term ionospheric prediction method suitable for China is proposed.By analyzing the long-term changes of the ionosphere,combined with the New Asia Oceania region rediction method on the basis of Recommendation ITU-R P.533;the solar cycle index derived from the critical frequency of F2 layer at a single station is replaced by the smooth sunspot number;the critical parameters of the ionosphere in different regions are established by introducing the geographical location parameters.The simulation results show that the prediction result of the improved method is more consistent with the reality.2.Aiming at the problem of poor anti-outlier performance of short-term frequency prediction,a method of oblique detection ionospheric Maximum Usable Frequency shortterm prediction based on robust Kalman filtering is proposed.By studying the variation law of the measured MUF data and the causes as well as characteristics of observation errors,and exploiting the ionospheric reference model as a priori information,the state estimation equation of the Kalman filter model was improved.The cost function mechanism was introduced to realize the measurement update of the forecast state through Huber-M estimation,and a short-term prediction method of tilting detection of a steady Kalman filter is proposed.The results show that the method can effectively suppress the forecast of the observed wild values in the project,and the prediction accuracy is better than that of the Kalman filter and the ionospheric reference model.3.Verification of the frequency selection model.The communication scheme of large-scale area short-wave emergency communication link was designed.Combined with the optimized long-short-term frequency forecast model,from the perspective of the maximum available frequency,proposed a fusion frequency forecast method with shortterm forecast as the main and long-term forecast as a supplement.The actual communication link test results show that the access rate of the selected frequency method in this thesis is higher than 79.17% in the range of 1 to 10 days in advance,and the access rate of short-time(1 to 2 days)can reach over 95%.