Ultrawideband (UWB) vs. Bluetooth 5.1 Direction Finding

What to choose as a real-time location system?

Do you want reliability?

Do you want repeatability?

Do you want stability?

Do you want accuracy? 

 

 

 
 

Then choose UWB.

Why?

Technology.

Our UWB technology is designed to give precise, reliable, stable and repeatable indoor location data. Other technologies (such as Bluetooth 5.1 Direction finding) are made for data transfer and only allow indoor location capability. UWB is made specifically for both. So choose UWB if you want reliable, repeatable, stable and accurate indoor location data. Why use Bluetooth if your process is based on indoor location? It’s like eating your soup with a fork when you know a spoon has been designed for it.

A dedicated system always has major advantages.

Multipath effects, also called reflections of the signals​.

UWB has major advantages in any environment where so called multipath effects (multi-path = multiple signals arrive at the receiver due to reflections of walls etc.) can occur. This effect occurs everywhere. Have you ever yelled "echo" in a large empty room? The echoes you heard are reflections. Imagine now many echoes can overlap each other and how difficult this would be to understand again. These difficulties extend to direction finding technology. A receiver has huge challenges when multiple copies of a signal arrive at it and overlay.

In Bluetooth 5.1, phase measurements of several receiver antennas can overlay due to reflections, which will result in inaccurate or even impossible measurements. In "clean" rooms (i.e. anechoic chambers) and well-defined propagation channels direction of arrival based on a multi-channel receiver will work, but real life use cases, industrial areas, buildings, etc. are different.

Measurement principle​.

 

UWB measures distance and can also measure phase between different receivers for Direction of Arrival, DoA. Bluetooth measures RSSI (Receive Signal Strength Indicator) and maybe DoA when there standard is ready and there will be receivers out there. Based on the distance^2 behaviour of the RSSI and the fluctuation of the signal power the distance measurement can only be called estimation, but not measurement. You can estimate close by, far away or very far away, but you cannot pinpoint and "measure" and say its accurately 8.23m. The DoA is based on phase measurements which undergoes phase fluctuations and multipath and is therefore often not as accurate as claimed.

Accuracy​​.

Bluetooth 5.1 Direction Finding claims pinpointing down to the centimeter. Well let's consider an optimal case and the direction finding principle:

Imagine you have a direction, which says in an optimal case 0° +-5° (from the variance of 5° is a reasonable value). This means if you would know the object is in 10 meter distance the area which is 10° wide spans approximately 1.8 meter. Now if the object is 50 meter far away (which you still do not know, because you can measure only direction) this will result due to trigonometry to 8.87 meter variance. Imagine now a second direction of arrival node, it may narrow down the area and intersect at a certain point. But the variance of the phase measurement and hence the angle of arrival accuracy still depends on the distance that the object is away from a receiver.

Bluetooth 5.1 direction finding receiver accuracy

Bluetooth 5.1 standard.

The Bluetooth 5.1 standard is just about to be released. The news report hardware to be available in the next few years. UWB has already been on the market for a considerable time. It’s proven, deployed, reliable, repeatable, and accurate.
(April 2019)