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Four Questions to Ask Before Testing GPS in Consumer Devices
Outside of in-car satnav, satellite positioning capabilities used to be a rarity in consumer devices. But one glance at the lineup from this year's Consumer Electronics Show (CES) proves that GPS accuracy is an essential feature in all kinds of devices. This also proves just how vital effective GPS testing is to the success of a product.

From new fitness wearables and smart watches, to a smart pedal that can track your bike in the event of a theft, the CES lineup demonstrated how GPS (or to give it its proper title, GNSS, for Global Navigation Satellite Systems) functionality is now near-ubiquitous.

As GNSS capabilities become the norm, consumers expect accurate and continuous positioning information from their devices. Manufacturers who can't meet these expectations risk losing sales and reputation. But how can you ensure your device delivers the kind of GNSS experience your customers expect?

How Can I Ensure Positioning Accuracy?

When product designers choose a GNSS chipset or module to integrate into a new device, they're swamped with options. And it’s not as simple as picking the cheapest or most readily available tech.

You need to consider whether you order a pre-built module, or integrate the GNSS receiver into the device yourself. You also need to understand which chipsets support which GNSS satellites, to what degree of accuracy, and ensure you have the right one to cover the regions you sell to.

But even after you've decided all of this, there's still far more to consider than just how reliably your device holds a signal. You need to test a variety of key areas to ensure GNSS performance covers the complete spectrum of functionality modern consumers expect.

What Areas Should I be Testing?

For consumer devices, there are a number of things you should consider when selecting your ideal GNSS receiver:
  • Time to First Fix – Customers don't like to be kept waiting, so you need to ensure that your device can find a GNSS signal quickly. This is especially true of multi-function devices like smartphones and the coming generation of smartwatches, where users will regularly turn location tracking off when not in use, to improve battery life.
  • Static and Dynamic Navigation Accuracy – If a user doesn't get pinpoint location accuracy whenever they need it, their trust in the device—and the brand that makes it—can be lost. There are many variables that can affect location availability and accuracy, including effects like multipath (where a satellite signal bounces off a nearby structure) and satellite obscuration (where buildings or other features in the environment obscure the device’s view of satellites overhead), so it’s best to test the receiver under as wide a range of conditions as possible.
  • Acquisition and Tracking Sensitivity – This defines the minimum level of satellite signal power for your chip to acquire the signal and keep hold of it. Many conditions affect the power level of already-weak satellite signals – including other electrical noise in the environment – and it’s important to know which conditions your receiver will cope with, and which it won’t.
  • Reacquisition Time – Tunnels, bridges, tall buildings, electrical or atmospheric interference: the average device will occasionally lose its fix when faced with these obstacles, and you need to be sure it can find a fix again quickly when the interference or obscuration has passed. A classic scenario is a driver emerging from an underground car park: can the navigation system pick up a signal again quickly enough to let them know whether to turn left or right?
  • Susceptibility to Radio Frequency Interference – GNSS chips are sensitive, and both accidental interference and purpose-made interference sources like GPS jammers can completely block your device from receiving and maintaining an accurate position. If signal interference could cause problems for users of your device, you need to know how it behaves in the presence of interference, and build in interference-mitigation measures which you will also need to test.
How Should I Compare my Options?

You could take your design prototype outside and observe how it performs in the live signal environment, but this will only let you test a small range of conditions and scenarios. And even if you test each GNSS module in the same location, the results will never be comparable, as the live RF environment changes all the time.

By using test equipment that can simulate – and repeat – many different conditions, you can test GNSS chips to ensure they cover all of the use cases they need to. Each GNSS chip you evaluate will be tested under the same conditions, so you're able to compare them accurately.

What if I Can't Test in This Way?

Not every R&D department will have this kind of test environment and GNSS test expertise available to them. In this case, it's worth looking for a specialist test partner that can build test cases and scenarios for you, and carry out the tests if need be. If you'd like expert assistance with setting up a GPS/GNSS test bed, and/or creating tests and test scenarios, we'd love to help.

By: Rahul Gupta - 4/30/2015 11:45:20 AM
Tags: GPS Testing

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