Introduction to Indoor Positioning

Bluetooth Low Energy (BLE)

What Is BLE?

Bluetooth Low Energy (BLE) is a low energy implementation of Bluetooth. Created in 2001, BLE was an attempt to fill the gap that the Bluetooth SIG perceived in contemporary wireless offerings for low energy and low-cost wireless protocols. BLE was slow to take hold, but it accelerated exponentially after its first inclusion in a smartphone in 2011.

BLE was designed from the ground up to have a similar range to Bluetooth “Classic” (about 330 feet) while using significantly less power than its predecessor. In order to conserve power, the data transfer rate for BLE is about one tenth and the latency is about five times that of standard Bluetooth. While BLE isn’t a powerhouse for transferring tons of data, it’s an excellent technology for applications with low data transfer requirements—like indoor tracking—where data can be sent in small chunks periodically.

How Does BLE Track Location?

All configurations for a BLE network rely on two major components: BLE beacons and a BLE hub for sending data to the internet. These components can then be combined in two different ways. The first configuration places the low powered beacons in the environment and relies on mobile hubs (e.g. smartphones) to send data and signal strength measurements to the internet. The second layout places the hubs in the environment and positions the low-power tags on trackable assets such as a crate of inventory in a warehouse.

Once a configuration is chosen, the means of calculating location are essentially the same. For rough proximity calculations—such as whether a person carrying a hub is near a forklift, or whether a person is walking through a large room—the existence of a known tag or hub in that area can be used.

When more precision is required, BLE relies on RSSI values to calculate how close a beacon is to a hub using a complex formula called trilateration. The formula relies on knowing several defining characteristics of the BLE hub being used. These distance calculations are then combined across at least three hubs to triangulate a location. Unfortunately, RSSI distance calculations are tricky and can be unreliable. Most commercial systems aid these calculations with additional information. The most common way of aiding these calculations is to map the RSSI values in a building after setting up all the hubs and then to use this known set of values to assist your triangulation calculations.‍

A Software Problem

The hardware for BLE tracking is relatively commonplace. Getting started is as simple as picking up some BLE beacons and provisioning them through a smartphone. On the other hand, the software for BLE tracking is where all the magic happens. Several companies that provide BLE tracking as a service already exist. Each has their own flavor of implementation. Very few of these applications rely purely on BLE. Typical technology pairings include Ultra-Wideband (UWB) and Ultrasonic tracking. Combinations like these are common because each technology has its strengths and weaknesses. No single indoor tracking method works perfectly on its own—yet.

Conclusion

BLE is a relatively well-established method for indoor tracking, but the indoor positioning space is still quite new and uncertain. Technological fragmentation and a lack of any “one-size-fits-all” solution means that implementation can be messy. With low power consumption, relatively high range, and potential for 1-2-meter accuracy, BLE is an excellent option among many. BLE still works best when complemented with other technologies that help it become as effective as possible. It’ll be interesting to see the role BLE takes in shaping the future landscape of indoor tracking.