The GNSS module is present on the front panel of the Cisco ASR-920-12SZ-IM router. The GNSS LED on the front panel indicates the status of the module. The following table explains the different LED status.

When connected to an external antenna, the module can acquire satellite signals and track up to 32 GNSS satellites, and compute location, speed, heading, and time. GNSS provides accurate one pulse-per-second (PPS), a stable 10-MHz frequency output to synchronize broadband wireless, aggregation and pre-aggregation routers, and an accurate time-of-day (ToD).

Note	The Cisco ASR-920-12SZ-IM router can also receive 1PPS, 10 MHz, and ToD signals from an external clocking and timing source. However, the timing signals from the GNSS module (when enabled) take precedence over those of the external source.

By default, anti-jamming is enabled on the GNSS module.

The GNSS module has the following stages of acquiring and providing timing signals to the Cisco ASR-920-12SZ-IM router:

• Self-Survey Mode—When the router is reset, the GNSS module comes up in self-survey mode. It tries to lock on to minimum 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. If you want to change the tracking data, use the no shutdown command to set the GNSS interface to its default value.

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 self-survey mode.

• 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.

Note	GLONASS and BeiDou satellites cannot be enabled simultaneously. GALILEO is not supported.

When the router is reloaded, it always comes up in the OD mode unless:

• the router is reloaded when the Self-Survey mode is in progress.

• the physical location of the router is changed to more than 100 m from it’s pre-reloaded condition.

When the GNSS self-survey is restarted using the default gnss slot R0/R1 command in config mode, the 10MHz, 1PPS, and ToD signals are not changed and remain up.

The GNSS is a fixed module on the Cisco ASR-920-12SZ-IM router and requires a license to enable the functionality.

After installing the license, you must enable it by using the license feature gnss command.

Note	The GNSS module will shut down, if it is in use and the license is disabled.

Note	To know more about the commands referenced in this document, see the Cisco IOS Master Command List .

• Enabling the GNSS License (Required)
• Enabling the GNSS on the Cisco Router (Required)
• Configuring the Satellite Constellation for GNSS (Required)
• Configuring Pulse Polarity and Cable Delay (Required)
• Configuring Cable Delay (Required)
• Disabling Anti-Jam Configuration (Optional)

gnss slot R0
no shutdown
anti-jam disable
constellation glonass
1pps polarity negative
1pps offset 1000 negative