The GNSS module has the following stages of acquiring and providing timing signals to the Cisco router:
Self-survey mode - When the router is reset, the GNSS module comes up in self-survey mode. It tries to lock on to a minimum
of four different satellites and computes approximately 2000 different positions of the satellites to obtain a 3-D location
(Latitude, Longitude, and Height) of it current position. This operation takes about 35 to 40 minutes. During this stage also,
the module is able to generate accurate timing signals and achieve a Normal or Phase-locked state.
When GNSS moves into Normal state, you can start using the 1PPS, 10 MHz, and ToD inputs from GNSS. The quality of the signal
in self-survey mode with Normal state is considered good enough to lock to GNSS.
Over determined clock mode - The router switches to over determined (OD) mode when the self-survey mode is complete and the
position information is stored in non-volatile memory on the router. In this mode, the module only processes the timing information
based on satellite positions captured in self-survey mode.
The router saves the tracking data, which is retained even when the router is reloaded.
The GNSS module stays in the OD mode unless one of the following conditions occur:
A position relocation of the antenna of more than 100 meters is detected. This detection causes an automatic restart of the
A manual restart of the self-survey mode or when the stored reference position is deleted.
A worst-case recovery option after a jamming-detection condition that cannot be resolved with other methods.
You can configure the GNSS module to automatically track any satellite or configure it to explicitly use a specific constellation.
However, the module uses configured satellites only in the OD mode.
GLONASS and BeiDou satellites cannot be enabled simultaneously.
When the router is reloaded, it always comes up in the OD mode unless:
When the system restarts GNSS self-survey by using the default gnss slot R0/R1 command in config mode, the 10MHz, 1PPS, and
ToD signals are not changed and remain up.