Research On Hf Channel Fast Detection And Link-establishing Technology

HF communication is a medium-to-long-range wireless communication form.Due to the fast time variability and non-cooperative competition characteristics of HF channels,it is necessary to detect channel quality to select high-quality channels before formal communication.However,the detection of different channels consumes a lot of time,which not only reduces the communication efficiency,but also makes the detected channel quality parameters lose timeliness.In view of this situation,this article will study the methods of fast detection and link-establishing to improve communication efficiency and ensure the timeliness of channel quality parameters.In this article,the channel detection time is shortened by introducing spectrum prediction technology before detection and link-establishment;by introducing a new link quality analysis(LQA)algorithm after detecting channel quality parameters,better quality channels can be screened out.In order to obtain the spectrum prediction data and the channel state parameters in the link quality analysis,a threshold is needed to convert the power spectral density values which represent HF channels into state values which represent the channel busyness.For the case where the existing threshold is not suitable to the HF channel,this paper proposes a threshold based on GM-HMM.This threshold models the relationship between the channel states and the measured power spectral density values as GM-HMM,and determines the threshold based on the obtained model parameters.The results show that the threshold based on GM-HMM can more accurately divide the idle state of the channel than the existing threshold.A method that combines information entropy with HF spectrum prediction is proposed in this article.It uses entropy to measure the predictability of the busy or idle states of HF channels,and uses mathematical tools to convert the predictability to the accurate prediction rate.Under the guidance of this theory,the limits of the time improvement brought by the introduction of the spectrum prediction algorithm is quantified.Seeing the problem that the traditional link quality analysis method cannot fully reflect the channel quality,a new link quality analysis method is proposed.This method introduces channel state parameters to assist in the calculation while considering the channel quality parameters.Through the new link quality analysis method,we can screen out channels with longer continuous idle time and greater idle probability,so as to ensure the continuity of communication to a certain extent and avoid the performance overhead caused by frequent channel switching.In addition to the above three main contributions,three other major tasks have also been implemented in this artical: design of the rapid detection and link establishing protocol;simulation of the signal transmission and reception process;channel parameter estimation at the receiving end.These three parts of work complement the above three major contributions,making this article a self-consistent and coherent whole.