Research On The Technology For Burst Communication Over The Horizon Take Advangtage Of Sporadic E

The sporadic E(i.e.Es layer)is a layer with high electron density,which is instantaneously and sporadicly created by some local regions of the E layer in ionosphere.It can transmit VHF radio wave back to the ground via entire reflection,partial reflection or scatter,and such an elbow pipe type over-the-horizon transmission can usually continue for a longer time(lifecycle of Es).Its maximum available frequency range is as wide as 200 MHz,and its single-hop communication distance can be 0~2600km.Although the Es burst transmission has smaller single-hop distance,its lifecycle is much longer than the meteor burst(MB)communication channel.Therefore,a remote distance burst-mode VHF communication system with perfect performance can be constituted by mans of one set hardware with two communication modes,i.e.the Es and the MB,which can be automatically switched to either of the two statuses to make their superiority compensated with each other.This thesis researches in depth on the related key techniques in a VHF Es channel burst-mode communication,as well as some method to switch the two communication modes,including the Es channel property analyzing,anti-multi-path-fading in the Es mode,adaptive data-rate varying in modulation/demodulation,VHF burst channel exploring in real time,channel pattern recognition,allowable transmission rate estimating,etc.The Es channel has an important characteristic different from the MB channel,i.e.,its transmission lost resulted from multi-path-fading has greater range and more complex varying rule.Therefore,for constituting an Es & MB hybrid communication system,the adaptive algorithm about selecting modulation mode,coding method and data-rate appears to be more complex;of course,it has greater potential in raising efficiency.It is desired that the system can detect channel property in real time,accurately recognize channel pattern and estimate allowable transmission data-rate,so as to be able to make the system fine matched with the channel and to reach the best system performance.Basing on the above researches,we have built an Es & MB hybrid-mode ultra-long-range burst communication demonstration system,and reached the goal that communication capacity is greatly raised and communication application performance and quality of service has remarkably improved.System simulation and indoor test results show that the demonstration system has many advantages,e.g,transmission in sporadic Es period,Es & MB dual-mode compatibility mode can be achieved a rate of 4kbps ~ 256 kbps for the service of data,voice,and low speed in FIG,as well as other services.Its annual traffic is 10 times more than that of a single mode MB system;moreover,its communication waiting time has significantly shortened and the timeliness for emergency communications has clearly improved.It provides a powerful and reliable tools for strategic communications under special conditions.