Research On Technology Of Improving The Availability Of Navigation And Position Under The Poor Environment

In the application environment of the satellite navigation receiver, availability is vulnerable to various environmental factors. For instance, the capability of message error correction is limited in the environment of high error message, the conventional methods of positioning is not available in the environment of inadequate visible satellites, positioning accuracy gets down under motorized environment, etc., will lead to decreased availability. In response to these problems, this paper studies the message integrity, the modeling of receiver clock error and navigation solving process, and studies the disadvantages of traditional processing methods, proposing the optimal design method. This paper does the research work from the following three aspects:(1) The traditional BCH error correction method have the problem of only correcting 1bit error, so this paper proposes a method of parameters error correction based on limiting orbital. The method identifies and corrects the error bits through the analysis of the physical meaning of message parameters and the limited range of the parameters. Simulation results show that the proposed method of error correction can correct 2 more error bit for some high bit error messages having limited range of parameters. At last, this paper summarizes the error correction rate of the parameters of each message setting BDS(Beidou System) ephemeris as an example.(2) The traditional prediction model of clock error based on polynomial has the problem of poor short-term forecasting accuracy, so a prediction model of optimal UC sliding window based on the smallest error variance is proposed. This paper analyses the principle of influence of the length of UC sliding window on short-term prediction accuracy, and proposes a prediction model of UC sliding window based on the optimal length of sliding window. The analysis of measured data shows that, compared with the traditional clock error model based on polynomial, short-term forecasting accuracy can be improved from 19 ns to 0.1ns. At the same time, the paper analyses the influence that the precision of clock error gives to adjuvant positioning performance.(3) The traditional arithmetic of satellite orbit extrapolation mostly forecasts extrapolation precision in several hours,lack of detailedly research of orbit extrapolation in long time, compare the extrapolate orbit with the orbit that IGS gives,then analyses the result on the research of satellite orbit extrapolation in long time.Experimental data results show that orbit predicted error is decreasing while increasing the simulating times,and changing peiodically.The error is generally increasing when prolongs the prediction times at the same time.At last, this paper summarizes the results of the research carried out, and discusses the forthcoming work.