What is CNSS?

CNSS is the Compass Navigation Satellite System, which will eventually comprise up to 30 medium-earth-orbit satellites and five geosynchronous satellites to provide true global coverage. This Chinese system is distinct from that country's existing Beidou I satellite system, which has been operating since 2003 but provides only domestic coverage using three geosynchronous satellites.

Like other systems, the CNSS will provide two levels of service. The free service for civilian users will offer positioning accuracy of within 10m, velocity accuracy of within 0.2m/s and timing accuracy of within 50ns. There will also be a licensed service with higher accuracy for authorised and military users only. The CNSS will initially cover China and its neighbouring countries only, but will eventually extend into a global navigation satellite system.

The CNSS ranging signals are based on the CDMA principle, like GPS and Galileo. And the frequencies for Compass are allocated in four bands - E1, E2, E5B and E6 - that overlap with Galileo. This overlapping could be convenient for multi-GNSS receiver design, but it also creates the potential for interference, especially within E1 and E2 bands allocated for Galileo’s publicly regulated service.

Although no signals are yet available for the CNSS, Spirent's constellation simulators are “Compass-ready”, and will be capable of simulating both Compass and Galileo signals to allow designers to address these issues with receiver design.

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