A New Common-view Based Timing Method

Time is closely related to people’s daily life. The work of broadcasting standardtime signal is called time service. In ancient time, sound is used to provide timeservice, such as beating bell and drum, and then light is used. Today, most timingmethods are based on radio wave with improved accuracy. Currently, the accuracy ofone-way timing method can reach about15ns.For users of nanosecond requirement of accuracy can only turn to common viewtime transfer and Two Way Satellite Time and Frequency Transfer methods. However,these methods need high cost equipments and only can be applied to few users. Allthese limitations compel us to advance a new timing method.Based on the analysis of both one-way timing method and common-view timetransfer, a new common-view based one-way timing method is proposed which canprovide accuracy of3~5ns. This paper focuses on this method and mainly discussesthe following aspects.（1）Proposal of the new timing method.Time service is different from common view in essence. As a timing method, itrequires disseminate timing signals in real time for mass users. While common viewcan only realize the time comparisons between fewer users after data exchange.The method overcomes these shortcomings by monitoring timing signal ofsatellites with receivers located at master station and then broadcasting to users. Thisequals to observe the same satellites with users. These data are used to correct the userreceiver’s measurements after received. Finally, the local time of users aresynchronized to the standard time UTC(NTSC).（2）Experiment verification of the new method.In order to testify the feasibility of the new method, a test platform is set up. Thezero-baseline experiment, short-baseline experiment and long-baseline experiment arecarried out based on it. The results of zero-baseline and short-baseline experimentsvalidate the feasibility of the new method. Influenced by the longer baseline and theunknown time difference between two Changchun and Lintong stations, the result oflong-baseline experiment is affected by the correction error of ionosphere delay andother space-related errors.（3）Proposition of the virtual common-view reference station technology. According to locations of users and reference stations, the relativity of ephemeriserrors and ionosphere delay errors are explored by Virtual Common-View ReferenceStation technique (VCVRS) for interpolating the observations of a non-existedreference station close to user. This method makes use of measurements of serveralreference stations and solves the problem of decreasing accuracy with the increasingdistance between user and reference stations.Some further researches about VCVRSare discussed. Firstly, the effects of different reference station number and differentmethods of weight determination on timing accuracy of the new method are studied.The fundamentals for users choosing reference stations are established and the impactof time synchronization errors is analyzed after that.（4）Research on the changing characteristic and broadcasting methods of timingdataTo ensure the real time and user capacity, the modeling and broadcasting oftiming data must be considered. Three methods are provided for data dissemination.The first one is based on communication satellite which is used to broadcast timingmodel parameters for users in real time. Internet is the following one which releasetiming data files each day for user’s download. The last one is short message enquirewhich waits the query command of users and then response.（5）Scheme design of the new timing system.The whole system of common-view based timing method is planed and designed.The detailed design of each part is also layout.