What’s the difference between a smartphone and IoT device? Lots of things, starting with GPS performance.
Hence the questions that consumers often ask: “My phone’s GPS always works flawlessly, but my fitness tracker gives me different distances when I run the same route. Why?” Or: “My phone always shows exactly where I am, but my dog’s tracking collar shows her a block away. Why?”
They’re reasonable questions — and ones to keep in mind when designing IoT devices not only for consumers but also enterprise applications such as asset trackers.
Two more things to keep in mind are weak signals and zero noise floor. Compared to smartphones, IoT devices often have to make do with extremely weak GPS signals, so they operate near the absolute noise floor. That means even a tiny amount of interference can ruin accuracy.
On top of everything, the IoT market is notoriously price sensitive. This increases challenges for device designers because they have to use low-cost components and forgo noise filtering to keep their device at its target price point. This exacerbates the noise problem. In fact, even when an IoT device passes basic CE/FCC tests with flying colors, real-world noise can still ruin GPS accuracy and reliability.
Smartphones’ Two Secret Weapons in the Battle Against Noise
There are two major reasons why smartphones provide better GPS performance:
- They don’t rely only on GPS. Smartphones also use Assisted GPS (A-GPS), which pulls data from cellular networks to speed up satellite lock.
- Cellular as a location backup: If GPS fails, phones can use cellular triangulation for location.
IoT’s Missing Piece: Many IoT devices don’t have a cellular modem and instead use Wi-Fi, Bluetooth, or another short-rage wireless technology to connect to a cellular device. As a result, those IoT devices have to make do with noise-attenuated GPS signals alone.
The good news is that IoT device designers can leverage A-GPS, cellular triangulation, or both. There also can be a solid business case for doing so. Even in price-sensitive markets, users may be willing to pay a premium for IoT devices if they provide noticeably superior performance. Higher accuracy and reliability also can help an IoT device stand out from the competition.
One example is asset tracking, where paying a bit more for a reliability and accuracy can be significantly cheaper than dealing with false alarms about geofence excursions. Another example is fitness wearables because buyers want to be certain that their new personal record reflects their extra effort rather than their device’s inaccuracy.
Power is another factor. Low-cost IoT devices often prioritize battery life over accuracy, leading to noise issues. But that’s not an issue for devices that have regular access to power, such as wearables that users charge every night or asset trackers that draw power from their host vehicle.
Top Tips for Maximizing GNSS Performance
When it makes business sense to leverage cellular, make the most of it. Start by choosing higher-quality antennas and noise-resistant components, like those in smartphones. For example, when comparing GNSS antennas, focus on the six top performance-related antenna parameters. (See “Six Key Parameters to Consider When Comparing GNSS Antennas.”)
Don’t undermine a great GNSS antenna with poor integration. Ensure that it’s far enough away from RFI sources and that it has an adequate ground plane. (For more tips, see “Key Considerations for Timely GNSS Antenna Integration.”)
There’s no shortage of cellular technologies to choose from, such as 4G LTE-M and NB-IoT to 5G RedCap. One consideration is their ability to support A-GPS via the cloud in terms of bandwidth and latency. Cost, coverage, and future proofing are three additional considerations. (For a deeper dive, see “4G vs. LTE vs. 5G: How Mobile Technology is Evolving.”)
Many IoT devices have ultra-compact or unusual form factors that off-the-shelf GNSS antennas literally can’t fit. In those cases, consider Laser Direct Structuring (LDS), which uses polymer resins to create an antenna in a 3-dimensional plastic carrier. This provides greater design flexibility than metal stamped or flexible adhesive antennas. (For more information about LDS, see “Leverage Innovative New GNSS Antenna Manufacturing Technologies to Ensure High Performance Even with Complex Form Factors.”)
For demanding or mission-critical applications, considering implementing multi-constellation support, such as GPS + GLONASS + Galileo. If one constellation’s signals are too attenuated by noise, the device can switch to another constellation.
Bonus: Multi-constellation support enables single-SKU IoT devices that can be sold globally. That’s one reason why over 30% of GNSS receiver chipsets support multiple constellations. (For more information about why and how to use multiple constellations, see “GNSS vs. GPS: Choosing the Right Technology for Precision and Coverage Needs.”)
