Evaluation method research on GNSS signal-in-space continuity

As a statistical measure of the frequencies of satellite navigation system performance loss, continuity is an important embodiment of satellite navigation system reliability evaluation. In fact, the continuity index is initially developed from the demand of civil aviation users and mainly focus on the service layer. The signalin- space continuity concept is not clearly put forward in GPS SPS PS document until 2008, relevant standard system is not yet mature and there are few results of the study on GNSS signal-in-space continuity evaluation. So this paper first studies the relationship between signal-in-space continuity and service continuity through analyzing the development of continuity index. And further analyzes specific connotation of signal-in-space continuity from the basic concept, index system. Then this paper studies the evaluation method of signal-in-space continuity based on the principle of basic reliability, and takes GPS for example to statistic all the unscheduled outages happened from 1999 to 2013 and calculates the mean time between failure to evaluate GPS signal-in-space continuity. The result is consistent with the performance standard announced by the GPS SPS PS (2008), which verifies the rationality and validity of this method. The method of evaluating signalin- space continuity proceeded in this paper is to provide theoretical reference for the test and evaluation of BDS performance.