Have you ever noticed that your smartphone can pinpoint your location with far greater accuracy when you’re outside than when you’re indoors? That’s because GPS accuracy has been steadily improving over the years, largely thanks to changes in satellite and receiver hardware. Besides, one or two meters here and there doesn’t mean much when walking down the street.
However, one or two meters indoors can be the difference between the living room and the bathroom or the meat aisle and the fresh produce section.
Currently, smartphones are able to achieve indoor accuracy of slightly less than 10 meters, which is insufficient for anything else apart from very course location tracking. Fortunately, there’s already technology available that will improve indoor accuracy to the one-meter level, and its name is Wi-Fi Round-Trip-Time, or Wi-Fi RTT for short.
Wi-Fi RTT is a feature added to the IEEE 802.11 protocol by the Task Group mc (TGmc) of the IEEE 802.11 Working Group, sometimes referred to as IEEE 802.11mc. The purpose of Wi-Fi RTT is to allow devices to measure the distance to nearby Wi-Fi routers and determine their indoor location with a precision of 1-2 meters.
If you’ve ever used Google’s “Find My Device” service to see the last known position of your smartphone on a map only to see a marker vaguely placed at our house, you can probably already see where the need for Wi-Fi RTT comes from.
Unsurprisingly, Google has added support for the technology to Android 9 Pie, and it has promised to add support for Wi-Fi RTT to the Google Wi-Fi mesh router. Other companies are likely to follow suit because Wi-Fi RTT could be a game-changer when it comes to home automation.
Just imagine waking up in the morning, walking into the kitchen, and hearing your coffee maker automatically turn on because your smartphone is aware of your exact location and programmed to tell your coffee maker to make you a cup of coffee when you enter your kitchen.
But Wi-Fi RTT isn’t just for individual smartphone users. Companies and organizations will be able to help their visitors get to where they want to go in a way that’s extremely convenient, modern, and potentially highly interactive and even monetizable. A shopping mall, for example, could display nearest discounts along with navigational information.
The key to understanding how Wi-Fi RTT works is round-trip time, sometimes referred to as round-trip delay. Here’s one concise RTT definition: network round-trip time is the length of time it takes for a signal to be sent plus the length of time it takes for an acknowledgment of that signal to be received.
Thanks to Wi-Fi RTT, smartphones will soon be able to use time-of-flight instead of signal strength to figure out how far away they are from Wi-Fi routers. With a single Wi-Fi router, you get the distance. With three or more Wi-Fi routers, trilateration (the process of determining absolute or relative locations of points by measurement of distances) with an accuracy of one to two meters becomes possible.
The users of Android P smartphones don’t have to be connected to any Wi-Fi routers for Wi-Fi RTT to work because only the smartphone is used to determine distance. Google has tied Wi-Fi RTT into Android’s existing location system to protect the privacy of its users. What’s more, Wi-Fi RTT transactions require the used MAC address to be randomized as a protection against the location tracking of individual smartphone users by unauthorized third-parties.
From the technical standpoint, virtually any modern 802.11ac router could support Wi-Fi RTT with a firmware upgrade. The unfortunate reality is that the manufacturers of wireless routers would much rather come up with brand-new products than many firmware upgrades for the existing ones simply because companies don’t make money out of firmware upgrades.
As we’ve already mentioned, Google has promised to add support for Wi-Fi RTT to the Google Wi-Fi mesh router, but the company has yet to act on its promise. So far, the only Wi-Fi RTT network certified products are:
| Broadcom 802.11ac Acculocate Access Point |
| Intel Dual Band Wireless-AC 8260 |
| Marvell AP-8964 802.11ac 4x4 Wave2 Concurrent Dual Band Access Point |
| MediaTek MT663X 802.11abgn/ac Ref. STA |
| Qualcomm IPQ4018 802.11ac 2-stream Dual-band, Dual-concurrent Router |
| Qualcomm IPQ8065 802.11ac 4-stream Dual-band, Dual-concurrent Router |
| Qualcomm Snapdragon 820 Development Kit |
| Realtek RTL8812BU |
To check Wi-Fi RTT support, you need to look up whether your Wi-Fi router comes with any of these Wi-Fi RTT network certified products. One such router is the Linux-driven Compulab WILD Wi-Fi router, which has the Intel Dual Band Wireless-AC 8260card.
According to Compulab, one WILD router can track other WILD routers with an accuracy of under 0.5 meters, making it useful for applications in retail, health care, transportation, logistics, manufacturing, smart buildings, and entertainment, just to give a few examples.
If you decide to purchase any Wi-Fi RTT-compatible router, it’s important that you use a professional Wi-Fi analysis tool like NetSpot to find the best spot for it and continuously monitor various aspects of your Wi-Fi network to achieve optimal performance.
NetSpot works with all with 802.11a/b/g/n/ac/ax wireless network adapters and supports 2.4 GHz and 5 GHz frequency bands at 20/40/80/160 MHz channels. You can download it for free and run it on a MacBook (macOS 11+) or any laptop (Windows 7/8/10/11).
Wi-Fi RTT is about to make indoor location tracking far more accurate than it is today. So far, there are only a few Wi-Fi RTT network certified products out there, but this will likely change very quickly considering that Google has already added support for Wi-Fi RTT in Android 9.
