Key Technologies On Ionosphere Scatter Communication System

Communication using the ionosphere is of great importance in the special communications industry because of the survivability of the ionosphere.Information can be transmitted over thousands of kilometers using ionosphere scattering,but ionosphere channel characteristics directly affect the performance of information transmission.In order to further enhance the performance of ionosphere scatter communication system,the key technologies on ionosphere scatter communication system are studied from two aspects: ionosphere scatter channel measurement and the design of information transmission scheme.The waveform design of the channel measurement signal for a single antenna system is considered on the studying of ionosphere scatter channel measurements.Zadoff-chu is studied from five aspects: ambiguity function,cross ambiguity function,complementary cumulative probability function of peak to average ratio,rate of frequency change and correlation function.The channel characteristic parameters are extracted by measuring data is used to establish the channel model and the time-varying channel capacity is given.In order to further understand the multipath characteristics of the ionosphere channel,the basic expansion model and serial correlation in frequency domain are used to analyze the variation of strongest path over a period of time.The simulation results show that base expansion model has the better performance,Serial correlation in frequency domain is better than serial correlation in time domain.Polarized multiple inputs multiple outputs system has been studied to cope with the low channel capacity of single antenna system and “Faraday” effect,two sequences including Zadoff-chu and its conjugate sequence are selected for polarized multiple inputs multiple outputs system,time division multiplexing and code division multiplexing are used to cope with the frequency selective fading of ionosphere channel,channel impulse response for four sub-channels are extracted by correlation processing algorithm,the channel matrix is extracted by two algorithms: the multipath energy accumulation and the maximum of multipath energy.The simulation results show that the designed multiple inputs multiple outputs system is satisfied the requirement of ionosphere channel measurement.Single carrier frequency domain equalization which is based on continuous phase modulation is the information transmission scheme of this paper.Firstly,the design basis of information transmission scheme parameters is introduced,and then the performance of different equalization methods are studied for single carrier frequency domain equalization in ionosphere channel and AWGN channel,and phase trajectory maps and state transition diagrams are described for different modulation indexes and the dimensions of modulation,then the demodulation process of continuous phase modulation based on maximum likelihood sequence estimation and the performance comparison for different coefficients in AWGN channel are showed,at last the performance analysis of single carrier frequency domain equalization based on continuous phase modulation is showed.