UWB and BLE indoor positioning systems demystified.
UWB vs BLE, which is better and why?
In these days when the real-time location systems (RTLS, calculation done in network) or indoor positioning systems (IPS, calculation done in the mobile device) are gaining more and more attention, one can see lots of comparison between Bluetooth Low Energy (BLE) and Ultra-Wide Band (UWB) around. Those comparisons in many times get quite funny tones due to happy mixing of the different terms from different abstraction levels or meanings. Below, I’m discussing some of the topics or even myths in a somewhat simplified, but hopefully understandable way targeting to clarify some of the topics.
Myth 1. BLE and UWB comparison is reasonable
Technically the most crucial difference from the strict positioning perspective between those two technology stacks is the used radio frequency and access technologies. Using UWB you can apply all three most common methods for positioning calculation including signal strength RSSI, signal angles AoA/AoD or signal timing TDoA/ToF. The radio technology used for BLE does not provide wide enough bandwidth and time resolution needed for time-based calculation algorithms. The positioning technology comparison itself is interesting, but it is only a small part of the picture. The application scenario and the business case dictate how other parameters like radio compatibility, 3rd party connectivity, installation efforts and other similar perks of the system should be emphasized, when the most feasible positioning technology is to be selected.
Myth 2. UWB does not provide global radio access
It is true that the 2,4 GHz ISM frequency band used by BLE stack is globally almost everywhere available. However, also the UWB and its mid-bands from 6 to 8.5 GHz do the trick globally in almost any of the countries. The generally used 2,4 GHz channel turns many times against itself when there are hundreds of users and devices in mass events like trade fairs or sports events simultaneously on-line.
Myth 3. The total cost of ownership (TCO) of UWB system is always higher
The TCO of the indoor positioning system is mainly consisting of the following components: devices & related hardware, installation costs, calibration costs, positioning tags, software and maintenance. If the hardware is working properly, the installation and devices dominate in the cost structure. One of the biggest differences is in the calibration method. The systems using angle-based algorithms (BLE) are required to be calibrated from the perspectives of time, angle and anchor positions compared to mandatory time and position aspects in the time-based algorithms (UWB). The UWB chip is currently few euros more expensive than the BLE alternative that brings a slight advantage to BLE in the tag side.
Myth 4. The tag battery lifespan of BLE is better
In direct comparison of the lowest average power consumption, the BLE is usually the winner. But if we see how tags are typically run, there is no difference in practice. In the BLE AoA or the UWB cloud calculation mode, the tag is typically firing the signal out and the network is receiving it and conducting the positioning calculation. All the other time, the tag is sleeping except maybe some dedicated time of receiving some tag update data downlink. In both modes the tag lifespan of more than a year with one hertz update rate is achieved with the off-the-shelf coin cell battery due to dominating receiving mode power consumption. Another story is the AoD of BLE or the UWB on-device calculation modes where the tag devices must be awake a way greater share of the time, where the tag lifespan collapses to a couple of days or weeks.
Myth 5. BLE is the only one that can be used directly on a mobile phone.
That is true for now generally speaking. Namely the BLE RSSI beacon technology is mobile phone compatible, but the RSSI as a positioning method baseline is highly inaccurate. UWB ToF/TDoA and also BLE 5.2 AoD are coming fast to mobile phones providing a way better indoor positioning experience than it used to be. Soon the mobile phone positioning experience is going to be seamless when moving from indoors to outdoors and vice versa.
Myth 6. UWB is more accurate than BLE
Well, this is depending on the circumstances. With UWB ToF/TDoA you can reach 10 centimeter or even better accuracy in the lab environment. But as we all know a lab is a lab and in practical use cases with UWB one can typically reach 0,5 to 1 meter accuracy with good probability and reasonable amount or anchors. But actually, with similar kinds of conditions, the BLE installation might reach the same performance.
Summary
In the RTLS/IPS application scenarios, there is no silver bullet offered. It is up to the use case what is the best choice for positioning technology. If you need better 3rd party connectivity you might favor BLE, but in case of the need for a simpler installation procedure the choice might be UWB. Also, within the technology providers relying on the same positioning tech, the solutions might be optimized for the different purposes emphasizing e.g. easiness of the installation, scalability or real-time features, etc. In the end, when considering investing in indoor positioning, it is the best way to go through the actual business case first and then go to the technical discussion based on the business case needs. Anyway, it is still sometimes fun to compare apples and oranges for the sake of the vivid discussion.
