How does the Fi Collar GPS/LTE-M tracking work?

The Fi Collar has been optimized to use a smart combination of GPS and cellular technology to locate your dog. Here we dive into the logic behind these location reports, as well as how the collar is able to achieve its incredible battery life.

What is GPS?

GPS is a global positioning system determined by a network of satellites that orbit the earth. These satellites regularly beam their locations down to earth, where GPS receivers (such as the Fi Collar!) can use the signals to determine their own location. The position accuracy of this location report depends on a couple of factors, including the number of satellites that the receiver can see and grab a signal from. A minimum of 4 satellites is required for any positioning, but often to get an accurate position a GPS receiver will need to see as many as 20 satellites with a clear line of sight! GPS signals also do not travel through structures (walls, buildings, trees, etc.) and will often rebound on hard surfaces, meaning indoor positionings are much more difficult to report.

When a GPS receiver tries to acquire a GPS location, it powers its GPS antenna and waits for signals from the satellites to come through (these move at the speed of light so come through pretty fast!). The power consumption of this operation depends entirely on the amount of time that the antenna needs to stay ‘on’ in order to collect enough data to be confident that its location is accurate.

For a lost dog device where power and battery life is so important, one of the key aspects of optimizing this operation is being able to predict how long the receiver should leave the power “on” for even when it does not have enough data to compute a location yet. For instance - if the receiver was on for 45 seconds and does not have enough data yet to send an accurate report...would an extra 25 seconds make enough of a difference?

We’ve optimized the Fi Collar for these exact operations - Fi uses GPS (US satellites) as well as GALILEO (EU satellites) and GLONASS (Russian satellites) to try to infer its own location as fast as possible and help your find your pup.

What is LTE-M?

LTE-M is the short name for the LTE CAT M1 network. Like the LTE used on cell phones, it’s a cellular network. The reason the Fi Collar needs to use a cellular network is because when your dog is lost, and out of reach of any Wi-Fi or owner’s cell phone, it will use GPS to compute its location, and then use the LTE-M network to send that location to Fi systems (and your Fi App).

As such it is always important for the collar to be able to access the network whenever it needs to.

Why is the Fi Collar not always connected to the LTE-M network?

As for GPS, connecting to a remote system requires the receiver to be turned “on” and powered by the battery. This operation is usually very costly on energy because the standard cellular networks were designed for your cell phones, and not tracking devices.

Cell phones need to always be reachable and are very heavy and big in size (which means they can have a large battery inside). People also usually recharge them every day, so they can use more battery for things like navigation.

On the other hand, tracking devices have very different constraints. We wanted the Fi Collar to be as small and light as possible (which means small battery) - in order to comfortably fit on your dog - and to only connect to the cellular network when needed in order to save battery. On pure LTE/3G/4G networks it unfortunately isn’t really possible to “only connect to the network when needed”. The connection operation requires a lot of data exchange, and so disconnecting/reconnecting to the network uses as much battery as basically staying connected to the network!

LTE-M solves this constraint - by allowing the devices connected to the network to specify when they will come alive on the network and use it. This allows for use cases where a receiver can “go to sleep” for a period of time, and come back alive on the network (and only then use its battery) when it needs to.

That’s how the Fi Collar achieves its incredible battery life. By combining logic for the collar to determine how to optimize the acquisition of a GPS location, and logic for how long to ‘go to sleep’ for vs. being connected to the LTE-M network, Fi can achieve 20x more battery life than previous generations of tracking devices.

While the hardware to support LTE-M is not that different, we took 2 years to develop and refine the nuances in the software to allow for these performances. That is also why other LTE-M devices coming to market now do not have the same kind of performance - the power savings are all in our proprietary algorithms.