In-Building Location and Tracking: Wi-Fi and 802.11az vs. Bluetooth LE Beacons

There remain more than a few IT pros who are unaware that unmodified Wi-Fi clients with no special or additional software or drivers can be located and physically tracked with the many Wi-Fi infrastructure and third-party products designed to do just this. The applications here are remarkable in scope and value: Consider an application that helps attendees navigate their way through a busy convention center. How about one that keeps tabs on children at theme parks? Need to know where critical personnel or equipment might be in a hospital? How about pallets of raw materials making their way through a manufacturing floor? Or a “panic button” app that could summon emergency help in whatever form required to a specific location within a building. You get the idea: This is just like GPS, but with greater accuracy and applicability to indoor applications, as GPS doesn’t work well indoors, especially in large buildings away from windows.

A similar function can also be accomplished with the Bluetooth Low Energy (BLE) increasingly built into mobile devices. The mechanism here is to install “beacons” that broadcast a unique ID that is seen by the BLE radio in handsets and other devices. Bluetooth has less range than Wi-Fi, so in general more BLE beacons are required than is the case with Wi-Fi APs, but some APs today also include BLE functionality, easing the way. In theory, once a device sees enough beacons, it can report this information to a server-side application that knows the precise location of each beacon seen, and thus the device is located, as well. In practice, however, BLE-based location and tracking is more about proximity to a given beacon than exact location, and here there’s clearly some application overlap among Wi-Fi and even RFID, QR codes, NFC and some IoT applications. All of this leads many network managers to ask the obvious question: Which one should be used, and in what circumstances? And, perhaps even more importantly, which will “win” in what many view as a technology war?

The answer is complex. Much depends upon the objectives of any given installation and application, along with, as always, cost-to-solution. Farpoint Group has long argued that a purely Wi-Fi-based solution is preferable in almost every case, since the infrastructure required is (again, almost always) already in place. In reality, some additional software, management overhead and even calibration (a walk-around exercise similar to a site survey) may be needed, so a declaration of “free” is perhaps stretching things just a little bit here. Still, the cost using Wi-Fi should be lower than the alternative, which might require perhaps a very large number of BLE beacons: Purchase cost, installation expense (mostly labor), database construction and maintenance, and the inevitable battery replacement cycle for each beacon all need to be factored in. And we have, in fact, used Wi-Fi-based location and tracking solutions that require no calibration, with overhead pretty much limited to importing a graphic of each floor of the facility and the occasional software update and with accuracy to one square meter. Pretty easy, indeed.

But there is a very valid complaint regarding Wi-Fi in this application: Location measurements have historically been based on received (by the client device) signal strength, also known as RSSI. Any given measurement of RSSI is suspect, since the path between a given AP and a given client is unknown for any given transmission, and signal losses greater than that inherent in flat (purely distance-based) fading can occur. But after taking enough samples, from multiple APs, rejecting the anomalous results, and doing a little match, we’ve been able to obtain accurate results in just a few seconds--with the dynamic tracking of moving clients similarly accurate, as well.

Still, it can be argued that such inherent variability really isn’t acceptable in mission-critical settings, and technology today allows us to do better--and with no significant incremental expense. The next generation of indoor location and tracking is on the way, via the upcoming 802.11az standard. 802.11az uses an entirely different mechanism for calculating distance. In this case, in place of signal strength we use round-trip timing of each transmission. As might be guessed, this requires the cooperation of the client in compliance with the standard, but this is easily implemented in software (although it could also be incorporated directly into the hardware of a given Wi-Fi chipset). Whereas signal fading is highly variable, timing is not, as radio waves propagate at very close to the speed of light in air and are only slowed a teensy bit (that’s a technical term) when passing through or bouncing off of non-air objects like walls. 802.11az-based solutions should thus have unprecedented accuracy and lower latency, and with enhanced privacy, as clients must actively engage in the process.

So, to return to the question at hand: Who’s going to win the Wi-Fi/BLE location/tracking/positioning wars, especially given this new development? We still hold with Wi-Fi here, although applications that require only proximity will often be implemented with BLE, especially given the robust hardware and software ecosystem that has built up around this technology over the past few years. And we also expect hybrid solutions using both technologies to become reasonably common. So, a winner? Yes, indeed, they both are, with Wi-Fi more common but BLE by no means a distant second.