Analysis of NavIC Signal for Loss of Lock Events at L5/S-Band Frequencies

Precise Point Positioning (PPP) is a system of acquiring the precise position of a user or GNSS (Global Navigation Satellite System) receiver without any errors. PPP is required in many applications such as navigation and military applications, airborne applications for civil and defense, and geodetic applications (glacier movement studies). The position obtained from GNSS receivers consists of errors that can range up to certain meters and for PPP the positional accuracy should be within mm. The majority of errors occur due to the ionosphere. Apart from this many other factors are responsible for degrading the positional accuracy of a user or receiver such as low C/No (carrier to noise density ratio of a signal), ionospheric scintillation, and receiver position (low latitude), low elevation angle, cycle-slip error. This research represents a detailed analysis of carrier range (cycles) at L5 and S1 to determine the severity of the cycle slip error and loss of lock problem in positioning. We have divided our work into two parts for the S1 frequency band the maximum time period is recorded where the loss of lock of a single satellite was occurring once and several times simultaneously multiple satellite (more than 1 satellite) data maximum period is also recorded when loss of lock event was taking place once and multiple times in a day. The second part consisted of an analysis of the total disturbed period of the L5 band where multiple satellites were unlocked and cycle slip error was also observed. The data preprocessing is necessary which is discussed in this paper so that zero-value data resulting from loss of lock of satellite (loss of radio signal) can be preprocessed or forecasted in real-time situations before positioning.