A Glance of GNSS and Its Future Trend
What first comes to your mind when you think about GNSS (Global Navigation Satellite System)? Direction navigation or elderly/kids position tracking? Nowadays GNSS positioning is no longer merely for car drivers to navigate the direction or parents to locate their kids remotely. Along with more accurate positioning and continuously utilizing services from GNSS, it has sprung up like mushrooms for applications such as drones, autonomous vehicles, and other location based services.
Global GNSS market is growing at a rapid pace, according to GSA GNSS Market Report, the market revenue from GNSS devices and services are projected to be €325 billion (approximately USD 352 billion) in 2029 comparing to €150 billion (approximately USD 162 billion) in 2019 with an 8% CAGR. GNSS devices in use are estimated to rise to 9.6 billion units by 2029 from 6.4 billion units in 2019, and among them, GNSS receivers are estimated to rise to 2.8 billion units by 2029 from 1.8 billion units in 2019.
GNSS (Global Navigation Satellite Systems) Overview
There are 4 global navigation satellite systems worldwide, which include GPS (from the USA), GLONASS (from Russia), BeiDou (from China), and Galileo (from European Union).
At first developed for military use, the GPS (Global Positioning System) is currently the most utilized satellite system, which could identify the locations with an accuracy of 10 cm or less. Already with 31 operational satellites across 6 orbital planes, the USA has further engaged in a modernization program to upgrade GPS. In 2020, 2 new GPS III satellites Vespucci and Magellan have joined the GPS constellation, featuring L1C signal and broadcasting L1/L2C/L5 signals.
Similar to GPS, GLONASS was originally developed for Russia’s military use. Currently there are 24 operational satellites across 3 orbital planes for GLONASS. the latest satellite generation GLONASS-K, which transmits CDMA (Code Division Multiple Access) signals, will soon replace GLONASS-M. In general, Russia continuously focuses on improving clock stability, new control, command and ODTS (Orbit Determination and Time Synchronization) technologies.
The BeiDou Navigation Satellite System (BDS) has started its development in 2000, and in 2020, 42 satellites are operating across 3 orbital planes. Furthermore, the third satellite generation BDS-3 has completed the full deployment; it shares resembling frequency bands and signal waveforms with GPS/GLONASS, which remarkably improves the interoperability among satellite systems.
The European Union (EU) started the development of Galileo from 2011, and now it has 24 operational satellites in 6 orbital planes. It has also planned to launch the new “Batch 3” satellites in 2021 to complement the first-generation constellation. Being a second mover in GNSS field, the EU puts effort on distinctive GNSS capabilities like SAR (Search and Rescue), HAS (High Accuracy Service), and navigation signal protection, etc.
| GNSS | Satellites | Orbital Planes | Current Status |
|---|---|---|---|
| GPS | 31 | 6 | New GPS III satellites Vespucci and Magellan feature L1C signal and broadcasting L1/L2C/L5 signals. |
| GLONASS | 24 | 3 | GLONASS-K will soon replace GLONASS-M, and Russia continuously focuses on improving clock stability, new control, command and ODTS technologies. |
| BeiDou | 42 | 3 | BDS-3 has completed the full deployment. It shares resembling frequency bands and signal waveforms with GPS/GLONASS. |
| Galileo | 24 | 6 | The EU puts effort on distinctive GNSS capabilities, and the new “Batch 3” satellites are planned to be launched in 2021. |
(Sourec: Wikipedia, GSA, summarized by TECHDesign)
Multiple frequency bands are used by all the global navigation satellite systems to achieve better performance and user experiences. In general, there are 3 frequency bands used by GPS, L1, L2, and L5 signals are centered at 1575.42, 1227.6, and 1176.45 MHz, respectively. For GLONASS, its satellites transmit the signals on the sub-bands of L1 and L2, with FDMA (Frequency Division Multiple Access) modulation. Another L3 signal, which is centered at 1207.14 MHz, is modulated by CDMA technique.
For BDS, B1, B2, and B3 signals are centered at 1561.098, 1207.14, and 1268.52 MHz, respectively. E1, E5, and E6 signals for Galileo are centered at 1575.42, 1191.795, and 1278.75 MHz, respectively.
Orange: No service; Yellow: Initial service; Blue: Full service (Source: GSA)
Future Perspective of GNSS: Multi-Frequency Capability
With continuous thirst of dependable PNT (Positioning, Navigation and Timing) services and cost effectiveness from consumers, GNSS and GNSS receiver providers are eager to create an even better user experience in the near future.
First, interoperability between different systems has been significantly taken into consideration. Adopting open signals from compatible frequency bands becomes ongoing plans for the system providers. On the other hand, the constellations from GNSS could broadcast the open signals they detect in common frequency bands. Therefore, multi-constellation GNSS receivers are currently in the mainstream.
To enhance the positioning accuracy, GNSS receivers with multi-frequency capability have come to the trend. Basically, the current GNSS receivers all support L1/E1 band, but with the increasing open signals in E5 band, dual-frequency receivers have gradually joined the market recently. It is expected to be more multi-frequency GNSS receivers in the market hereafter.
(Source: GSA)
In terms of design effort, antennas in receivers are the key elements to support multi-frequency function. For instance, using E5/L5 as a second frequency band is beneficial for more accurate positioning, but it is also difficult for antenna design. Previously the antenna designers had already needed to consider the trade-off between size and gain, and now they need to take multi-frequency support into account as well. Moreover, since modern GNSS signals have broader bandwidth than legacy ones, to design antennas which could match GNSS signals’ bands becomes another challenge.
To sum up, multi-constellation GNSS receivers are already put into market, and receivers with multi-frequency capability are one of the future trends. In the meantime, the design of antennas becomes even more important than ever. Overall, designers still face the challenge of balance among size, gain, bandwidth, and multi-frequency support.
Conclusion
Global GNSS market is growing at a rapid pace; the revenue from GNSS devices and services are projected to be €325 billion (approximately USD 352 billion) in 2029, according to GSA GNSS Market Report. GPS, GLONASS, BeiDou, and Galileo are the main global navigation satellite systems, and all of them are in the process of improving the positioning accuracy and related services by planning or implementing more satellites in the systems.
Multi-constellation GNSS receivers are already in the market, and receivers with multi-frequency capability will gradually be on the trend. It again brings up the importance of antennas in receivers and propels the improved design of antennas as well.
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