The developers of the GPS system would be amazed by the scope and variety of applications dependent upon it and its complementary systems today. As well as the US GPS, the timing community now has access to Russia’s GLONASS, the EU’s Galileo and China’s BeiDou systems as well as some localised enhancements such as EGNOS here in Europe. Most timing receivers will now be offered with multi-constellation support (whether ‘out of the box’ or via software license) or indeed multi-band support. What does this bring to you as a user?
Multi-Constellation will give you the option of taking data from more than one constellation (e.g., GPS and GLONASS). Therefore, the opportunity to ‘qualify’ the time base of constellations to secure yourself against a constellation error, such as the SV 23 issue with the GPS system in 2016 that introduced a 13ns spike in time that took many hours to resolve. In a multi-constellation receiver, this issue could be detected and GPS inputs would be ignored until it’s resolved.
Your position and time from a satellite constellation is calculated from data received from all satellites on position and on-board clock performance. Allowance is also required for the time these signals take to travel from these satellites to your position on Earth. All the GNSS constellations deliver data on several radio frequency bands. Each of these bands will have different time to travel characteristics. Utilising these differences enables the timing receiver to determine the position of each satellite it sees more accurately. It can then resolve better position and timing accuracy on the ground.
What Should I Do?
With many timing solutions now utilising a core number of GNSS receiver chips, multi-constellation is increasingly an out of the box solution. For example, the Microchip TimeProvider 4100 does not require additional licensing to enable multi-constellation.
Multi-band is at a different stage right now. Some timing platforms already require multi-band GNSS to deliver the increasingly stringent timing requirements of 5G networks. I am sure that it is just a matter of time until this becomes the case across all platforms. So, if your timing equipment supplier needs multi-band then it is wise to license this from the off.
Currently, we have yet to encounter a timing requirement that we cannot meet without the use of multiple GNSS constellations. I always recommend that the necessary multi-band antenna be installed from day one. There is a cost premium for this hardware. However, it beats having to revisit your rooftop installation. And the costs incurred in doing this just to switch on a software licence.
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