Information About the GNSS
Overview of the GNSS Module
The GNSS module is present on the front panel of the RSP3 module and can be ordered separately with PID=. However, there is no license required to enable the GNSS module.
The GNSS LED on the RSP3 front panel indicates the status of the module. The following table explains the different LED status.
|
LED Status |
Description |
|---|---|
|
Green |
GNSS Normal State. Self survey is complete. |
|
Amber |
All other states |
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 an 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 RSP3 module 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.
Operation of the GNSS Module
The GNSS module has the following stages of acquiring and providing timing signals to the Cisco router:
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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.
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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:
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A position relocation of the antenna of more than 100 meters is detected. This detection causes an automatic restart of the self-survey mode.
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A manual restart of the self-survey mode or when the stored reference position is deleted.
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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:
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the router is reloaded when the Self-Survey mode is in progress
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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.
Anti-Jamming
By default, anti-jamming is enabled on the GNSS module.
High Availability for GNSS
The chassis has two GNSS modules, one each on the active and standby RSP3 modules. Each GNSS module must have a separate connection to the antenna in case of an RSP3 switchover.
Prerequisites for GNSS
To use GNSS:
- 1PPS, 10 MHz, and ToD must be configured for netsync and PTP. For more information see the Configuring Clocking and Timing chapter .
- The antenna must have a clear view of the sky. For proper timing, minimum of four satellites should be locked. For information, see the Cisco NCS 4206 Series Hardware Installation Guide .
Restrictions for GNSS
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The GNSS module is not supported through SNMP; all configurations are performed through commands.
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On HA system, the traps from the standby system are logged to the console as the SNMP infra does not get enabled on standby RSP module.
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GNSS objects or performance counters are updated every 5 seconds locally and acknowledge the MIB object request accordingly.
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GNSS traps generation is delayed for 300 seconds for the first time after system startes to avoid any drop of GNSS traps.
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