In any case I doubt this has much practical impact given you presumably need an SDR to do this tracking.
The signature is based on physical layer characteristics, according to the linked paper : « They result in two measurable metrics in BLE and WiFi transmissions: Carrier Frequency Offset (CFO) and I/Q imperfections, specifically: I/Q offset and I/Q imbalance. ».
Yes, you would probably need SDR to do this tracking, but SDR are generally not this expensive.
> Mobile devices, including phones, smartwatches and fitness trackers, constantly transmit signals, known as Bluetooth beacons, at the rate of roughly 500 beacons per minute. These beacons enable features like Apple’s “Find My”--a tracking service to find a lost device as well as COVID-19 tracing apps; and connect smartphones to other devices such as wireless earphones.
> The current approach taken by smartphone companies to make the devices hard to track by their Bluetooth signals is to randomly change the phone’s identity, its MAC address. However, that doesn’t address the physical-layer fingerprints inherent in each device’s transmissions due to unique hardware imperfections.
> All wireless devices have small manufacturing imperfections in the hardware used to emit these beacons that are unique to each device. These fingerprints are an accidental byproduct of the manufacturing process. These imperfections in Bluetooth hardware result in unique distortions, which can be used as a fingerprint to track a specific device.
For example, your first question exposed that you had a misconception of what "beacon" means, and the first sentence of these excerpts is exactly an utter layperson definition of what "beacon" actually means.
I don't know how you can say "I read the article" and then read these bits yet a 2nd time, and still claim to have those questions.
SDRs and the software to make good use of them are cheap and readily available. Using them is well within the ability of almost everybody. All you need is the desire.
I’ve mainly seen “BLE beacon” used to refer to types of devices, especially ones that primarily advertise.
There are some devices, like BLE-based remote controls, that advertise very frequently, I assume to reduce latency between a user’s action and response by the receiving device. It makes for a very noisy environment if you’re playing at home and not filtering based on MAC, etc.