Multi-constellation Receiver's Fast Cold Start Algorithm

With the establishment and improvement of the global navigation satellite system(GNSS)and the regional enhanced constellations,and their compatibility with each other,the multi-star receiver has been vigorously developed and widely used.Multi-constellations have a definite advantage in providing more general,more sequential observational information,but it also leads to some sort of efficiency problem.In order to shorten the time to first fix(TTFF)of multi-constellation receiver cold start,this paper carried out a series of researches on the algorithm in the cold starting process of multi-constellation receiver.Firstly,new cold starting conditions are proposed according to the actual application,and the error effects of time and almanac are analyzed.Analyzes the two methods of cold start and the corresponding concrete steps,and points out the possibility that the serial mode can improve the efficiency of cold starting.The multi-channel collaboration of the receiver is illustrated to verify the feasibility of the serial method.Presents a method to unify the space and time frame of multi-constellation.Then,on the basis of the traditional visible star search algorithm,proposes the anti-shading visible star search algorithm.Analyzes it and indicates that the traditional algorithm is likely to degenerate into full constellation search and lose all efficiency.To solve this problem,the anti-shading visible star search algorithm uses the initial satellite group,the edge satellite group and the design of extension/shrink search,to maintain the performance of the most efficiency compared with the traditional algorithm under the condition of shading.In addition,based on the anti-shading visible star search algorithm,proposes a differential doppler visible star search algorithm.Analyzes that the principle of doppler effect contains the user's location information,and make the analysis of the composition of a doppler frequency shift observation,points out the feasibility of inverting the rough user's location.The differential doppler equation is proposed for the more accurate calculation of rough user position.Analyzes the user's location selection condition judgment method based on the differential doppler equation.The approximate calculation method of efficiency reference value is proposed and the error of approximate treatment is analyzed and the compensation method is given.The key factors that influence the cross-effect of zonal region are analyzed.The algorithm process is formed and the performance of the cold start efficiency under many observation conditions is improved.Finally,the visible star search algorithm based on doppler positioning is proposed.Analyzes doppler positioning principle,and the error and precision factor,and combines with the need of the algorithm to build doppler positioning equation with the elevation constraints.In calculating the userlocation at the same time,gives the parameter estimation of local frequency bias.The estimation method of precision factors and sorting indexes of different visible star combinations are given,and the compensation method for the user's position error is given.The algorithm process is formed and the efficiency of cold start is improved.