Research On HF Adaptive Processing Technology

High Frequency(HF)communication mainly relies on ionospheric transmission.It has the advantages of long transmission distance,cheap and robust anti-destruction capability,so its widespread uses in military and earthquake relief activities.In order to cope with the new demands of modern society,HF communication systems need to upgrade further.The upgrade direction of the fourth generation of HF communication is a high speed,high bandwidth and intelligence.Combining with Watterson HF channel model and ITS channel model,a simplified wideband High-Frequency channel model based on the measured channel data is proposed in this article.This model's bandwidth can achieve 40 kHz,exceeding the bandwidth limit of the original 12 kHz,and the model is simple and easy to simulate.When implementing the attenuation module of this wideband channel model,the Random Modulation Function in the ITS model is utilized.This thesis uses Sum-Of-Sinusoid(SoS)method to achieve the Random Modulation Function and proposes a parameter determination method based on offset,which can reduce system overhead.A Wideband High-Frequency Adaptive Processing System based on OFDM technology is proposed in this thesis.Applying the Adaptive Modulation Technology(AMC)of OFDM to the wideband HF communication system can effectively improve the transmission efficiency and transmission quality of the system.According to different adaptive criteria,these AMC algorithms can minimize the transmission power or maximize the throughput.In this HF communication system,channel estimation technology is used to provide channel information support for adaptive modulation.Due to the lag of channel estimation,there is a feedback delay in the channel estimation result so that it will affect the adaptive modulation performance of the system to a certain extent.This article briefly introduces Channel Prediction technology and then analyzes the advantages of OFDM Time-Domain Prediction Technology from a mathematical perspective.Finally,the possibility of combining it with HF Adaptive Processing System is discussed.After analyzing the characteristics of the wideband channel,this thesis describes the structure of the entire HF Adaptive Processing System and designs the appropriate OFDM parameters and frame structure.It is found that the performance of the Hughes-Hartogs Algorithm is optimal.The problem with the Hughes-Hartogs Algorithm is that the amount of calculation is too large.In the real-time communication system,to calculate the optimal value,a large amount of calculation time is consumed,which is not suitable in an HF communication system.According to different Adaptive Criteria,a Minimum Power Algorithm and a Maximum Throughput Algorithm based on Dynamic Subband Partitioning are proposed in this thesis.These two algorithms significantly reduce the computational complexity of the Hughes-Hartogs Algorithm and have high practicability.