GNSS platform cuts power, time-to-first-fix -

GNSS platform cuts power, time-to-first-fix


U-blox unveiled the M10, its latest GNSS (Global Navigation Satellite System) platform for low-power positioning applications. Designed entirely in-house, the U-blox M10 fits into a wide range of applications such as sports watches, trackers for goods, and livestock tags, all in a small form factor and with very long battery life.

The M10 is equipped with the company’s Super-S technology, which helps to filter noise and distinguish positioning signals. The device can acquire data simultaneously from up to four GNSS constellations even in inhospitable environments, such as urban canyons. Skyscrapers block  the line of sight between satellites and receivers, making it extremely difficult for GNSS receivers to lock on to signals emitted by satellites in orbit for long enough to locate themselves continuously. Increasing the number of satellites can make a significant difference.

In an EE Times interview, Bernd Heidtmann, product manager positioning at U-blox AG, highlighted how the M10 is designed to consume 12 mW in continuous tracking mode, a reduction of about 5 times over the parent company’s previous technology (M8).

“Super-S technology optimizes power consumption and accuracy with weak signals or small antennas. Short time-to-first-fix (TTFF) ensures low power consumption and Weak signal compensation feature improves position accuracy,” said Heidtmann.

Figure 1: u-blox M10 and u-blox M8 (Source: u-blox)

GNSS Platform

As we increasingly rely on on satellite positioning, we keep expecting greater positional precision. Thanks to the reduction in hardware and software electronics costs, there has been a great expansion in terms of applications and use cases.

The EU’s Global Navigation Satellite System Galileo allows GNSS receivers to ensure that satellite signals are actually coming from the Galileo satellites and have not been modified.  This approach makes it more difficult for hackers to do their “job.” The European GNSS constellation will be the first to offer free authenticated navigation messages to civilian users.

Galileo is the European Global Navigation Satellite System (GNSS), developed to provide position, navigation, and weather information to users around the world. Unlike other GNSS systems, Galileo is managed by a civil body, the European Space Agency (ESA), and has been designed in response to the needs of different user communities.

The Galileo satellite segment involves the use of 30 satellites (24 operational and 6 spare), in orbit at an altitude of over 23,000 kilometers. The satellites will be evenly distributed over three orbital planes and each will take about 14 hours to orbit the Earth.

The security approach used consists of affixing an encrypted authentication signature to GNSS navigation messages, which can be used to verify messages based on a hybrid symmetric/asymmetric key approach. GNSS data authentication will play an important role in advanced driver assistance systems, autonomous driving or any number of risky business activities.

U-blox Hardware

The U-blox M10 is designed to consume 12 mW in continuous tracking mode, keeping the draw low for battery-powered applications. The  M10’s increased RF sensitivity also reduces the time it takes the platform to reach a first fixed position when initialized, working well even with small antennas.

“The U-blox M10 chip size is 4×4 mm in a QFN package. The “MAX” module allows for integration with no external components needed. The “ZOE” form factor has the same functionality as MAX and NEO modules. And this is a so-called system in a package. It has the same functionality as the max module, but packed into only 20 square millimeters”, said Heidtmann.

Figure 2: the three modules, from left: QFN package, MAX module and ZOE form factor (Source: u-blox)

Two tests conducted in Australia and Germany have shown that even in harsh environments where large buildings can obscure the signal, Super-S and the improved “Super-E” mode allow even more power reduction with lower update rates, optimizing the measurement where the signal is very low (figure 3).

Super-S technology addresses two common challenges encountered in industrial tracking and wearable use cases: weak GNSS signals and inadequate antenna positioning, but also factors such as bad weather, obstructed sky views, and urban canyons adversely affect the quality of GNSS signals reaching the positioning receiver, reducing positioning performance. u-blox Super-S technology combines 2 different sizes to cope with these situations.

GNSS receivers can be in two operational phases: the acquisition phase and the tracking phase. In the first phase, there is higher sensitivity, and the acquisition time is reduced by obtaining a position with a higher probability and consuming little energy. In the next phase, the objective is to maintain the position.

Figure 3: Maximum position availability with concurrent reception of 4 GNSS in Australia (Source: u-blox)

Figure 4: Weak signal compensation in Germany (Source: u-blox)

“If you look at the picture, on the left of figure 3, you see a one and a two. With number one, you see that the buildings are not so high as in number two. And if you look to the right, you see all these colored lines stem, and green is the true path, really the true position. Then there’s M8 yellow and M10 in blue. And for number one, you see there’s almost no difference. They report basically the true situation. But if you look at number two, you see a difference. The yellow line is about 20 meters away from the green. And the blue line is about 10 meters away from the green. And there we see in such a scenario where you have really high buildings in deep urban areas, there it makes a difference to have 4 GNSS,” said Heidtmann.

He added, “if you are in this area, you cannot see every satellite because the buildings will give you a shadow. And if you can listen to all four constellations, you will catch up more satellites. And then, of course, this gives you a benefit, because there’s always a selection. So, the receiver will look at all the available satellites, and then would select the maximum 30 signals to track. But of course, in this situation, you don’t have 30, you are lucky if you have eight or nine,” said Heidtmann

Small antennas or bad antenna locations lead to poor RF signal strength. Weak signal compensation changes the receiver behaviour to adopt to this situation. “Drive tests showed >25% improvement on position and speed accuracy,” said Heidtmann.

Figure 5: block diagram of M10 (Source: u-blox)

Figure 6: u-blox M10 and M8 in comparison (Source: u-blox)

u-blox M10 features advanced spoofing and jamming detection. “Spoofing and jamming attacks are detected and reported to the host. Spoofing detection based on GNSS raw data analysis, and Spoofing attack mitigation by using an authenticated signal (Galileo OS-NMA),” said Heidtmann.

Critical applications need to know how much confidence they can place on their data that are acquired by receivers. The protection level describes the maximum position error and quantifies the reliability of the system. This level is influenced by all sources of error that commonly affect GNSS solutions.

“If, for example, a GNSS receiver determines its position with a 95% protection level of one metre, there is only a 5% probability that the reported position is more than one metre from its actual position,” said Heidtmann.

Innovations in systems and technologies related to the GNSS (Global Navigation Satellite System) sector are a process in constant and rapid evolution. The instantaneous accuracy of GPS at these levels was reserved for US Defence, but this triggered the race to create more reliable alternative systems that gave rise to GNSS (Global Navigation Satellite Systems) with contributions from several countries around the world, such as the Russian GLONASS, the Chinese Beidou and the European Galileo. Galileo data help to locate beacons and rescue people in distress in all kinds of environments.

>> This article was originally published on our sister site, EE Times.

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