From 13 June 2017, all new GNSS equipment sold in the EU must be tested to ensure activity in nearby frequency bands doesn’t interfere with performance. Here’s what you need to know.
If you’re launching a location-aware device in the EU, there’s a new ruling you need to get to grips with. From 13 June 2017, all new GNSS-reliant devices launched in the EU must be tested to ensure they will not be adversely impacted by activity in adjacent frequency bands.
The fine detail of the new EU Radio Equipment Directive (RED) is still being worked out, but here’s what you need to know now if you’re designing and developing a new GPS or GNSS-reliant device for the EU market.
Why is RED necessary?
With only so many bands in the radio spectrum, and so many internet, TV, radio, and positioning devices looking to make use of them, governments are under increasing pressure to release unused blocks of the spectrum.
But when it comes to the frequencies adjacent to those used by GPS and other global navigation satellite systems (GNSS), there is a risk that terrestrial signals will overpower the very weak signals emanating from satellites in space. And that can prevent devices that rely on those satellite systems from functioning as expected.
The risk was famously highlighted in the US in 2012, when broadband provider LightSquared moved to deploy a new wireless internet service using spectrum adjacent to GPS frequency bands. Before LightSquared could deploy its service, however, the GNSS community found evidence that it would cause major interference to GNSS devices. In light of the evidence, the FCC withdrew its permission for LightSquared to go ahead with its plans, contributing to the company’s eventual bankruptcy.
Pre-emptive action for EU GNSS devices
The RED is a pre-emptive move designed to prevent a similar situation from arising in the EU. In essence, it means that if you want to sell a GNSS-reliant device in the European Union, you need to make sure your device has undergone the necessary testing to prove its signal won’t degrade by more than 1dB when there is activity in adjacent frequency bands.
As a minimum, then, the onus is on chipset and device manufacturers to ensure their GNSS products comply with RED standards, including the GNSS adjacent band compatibility requirement.
Device manufacturers will also want to conduct their own independent tests as part of the CE (Conformité Européenne) and conformity marking process that shows a product conforms with EU law. This will add another set of tests to the existing test regime, but the tests are easily conducted in the lab and will provide peace of mind that the device will function as intended in the face of adjacent-band activity.
It is important to note that the GNSS RED requirement is not being applied retrospectively - existing products will not be required to meet the new adjacent band compatibility requirements, but all new equipment will have to be able to demonstrate that does in order to carry the CE mark.
But for manufacturers of devices that have a critical reliance on GNSS signals - whether for position or precise timing - achieving RED compliance is only the beginning. Even if adjacent band GNSS interference does not degrade the device’s Carrier to Noise Ratio (C/N) by the 1dB allowed by the EU directive, lower levels of interference inside the GNSS frequency bands may have the potential to cause positioning and timing irregularities
For instance, when Spirent took part in the STAVOG project to analyse the impact of GPS disruption on sea vessels, it found low-level interference could degrade signals, causing positioning readings to be out by up to 270 metres.
Unlike a full GPS outage, a degradation in the signals caused by in-band RF interference can often result in reduced performance of the receiving device, without any warning to the end user. In the worst case, a similar situation could occur with adjacent band interference, partially jamming a GNSS system and causing it to output inaccurate and even dangerously misleading data – all while the user is unaware that a problem has occurred.
The only way to know exactly how your device will respond to adjacent band interference is by extensively testing its performance across a range of scenarios.
Testing adjacent band compatibility
To thoroughly test for adjacent band compatibility and interference effects, chipset and device manufacturers will need to use a dedicated interference signal generator, a robust GNSS simulator, and a method to detect and measure the Carrier to Noise Ratio - the mandated performance metric for assessing the impact of adjacent band interference on GNSS devices as part of RED.
Beyond the hardware requirement, testers will need a test plan that ticks all the boxes of the RED. Though the directive is set to come into force soon (after a period of public consultation on the requirements), the full extent of testing requirements has yet to be confirmed. It is important to note however, that from 13th June this year, testing will still have to be undertaken against the existing draft document.
With this in mind, manufacturers that develop GNSS-reliant devices for the EU market will need to ensure that they have the appropriate test equipment and expertise needed to conduct the mandatory testing for Adjacent Band Compatibility when the time comes.
For more updates on risks to GNSS-reliant devices, you may also like to join the GNSS Vulnerabilities LinkedIn Group to stay up to date with current risks and regulations.
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