Ultra-wideband (UWB) for real-time location: how it works, range and accuracy

Ultra-wideband (UWB) is a radio technology that spreads its signal across a very wide slice of spectrum, typically 500 MHz or more per channel, rather than concentrating it in a narrow band. That width is the whole point: it allows extremely short pulses to be transmitted, and short pulses can be timed with far more precision than the longer, narrowband signals used by technologies like BLE or Wi-Fi. This is why UWB is generally the most accurate RF-based indoor location technology in common commercial use.

Key specifications

Actual performance depends on receiver density, bandwidth used, and how much multipath and obstruction exists in the environment, so treat these as general ranges.

How it works

UWB systems measure distance or angle rather than relying primarily on signal strength. As explained in our measurement basics guide, Time of Flight works by measuring how long a signal takes to travel between transmitter and receiver and converting that into a distance using the speed of light. Because radio travels roughly 30 cm per nanosecond, this requires very precise timing, precision that UWB's short, wideband pulses make practical in a way narrowband signals generally cannot match.

Some UWB systems use two-way ranging, where a tag and a fixed anchor exchange messages and measure round-trip time, avoiding the need for perfectly synchronised clocks between the two devices. Others use Time Difference of Arrival, where multiple synchronised fixed receivers each timestamp the arrival of a single transmission, and the differences between those timestamps are used to calculate position without requiring the tag to know precise time at all.

A further advantage of UWB's wide bandwidth relates to indoor environments specifically. As covered in our radio frequencies guide, reflected signals (multipath) are one of the biggest sources of error in indoor RF location. Because UWB pulses are so short in time, the direct-path signal is less likely to overlap with its own reflections at the receiver, making it easier to identify the true first arrival rather than a distorted, delayed one. Some UWB systems also support Angle of Arrival measurement using antenna arrays, and a small number combine AoA and TDoA in the same system for additional measurement redundancy.

Measurement methods available

• Time of Flight (ToF) / two-way ranging – distance calculated from signal travel time
• Time Difference of Arrival (TDoA) – position calculated from arrival-time differences across multiple synchronised receivers
• Angle of Arrival (AoA) – direction measured using an antenna array at the receiver, available in some UWB systems

Advantages

• Highest typical accuracy of the commonly used RF location technologies
• Wide bandwidth makes it more resilient to multipath distortion than narrowband RF
• Can support high tag density and frequent updates without accuracy dropping sharply
• Increasingly built into consumer smartphones and some IoT chipsets, expanding potential applications

Limitations

• Infrastructure and tag costs are generally higher than BLE, Wi-Fi or passive RFID
• Deployment typically needs a proper site survey and receiver placement plan to achieve rated accuracy
• Tag battery life is usually shorter than BLE, since more frequent, precise ranging draws more power
• Regulatory power limits on UWB emissions vary by region, which can affect achievable range

Typical applications

UWB suits applications where sub-metre accuracy genuinely matters: tool and asset tracking on production lines, safety systems that need to confirm a person is or isn't within a defined zone, process control tied to precise location, and any use case where the cost of the system is justified by the precision it delivers.

Frequently asked questions

Is UWB more accurate than BLE? Generally yes. UWB typically achieves accuracy in the tens of centimetres, compared with metre-level accuracy for standard BLE RSSI-based systems.

Does UWB work through walls? UWB signals can pass through some materials, but accuracy and reliability degrade with obstruction, similar to other RF technologies. Direct line of sight to enough receivers generally produces the best results.

Why is UWB more expensive than BLE or Wi-Fi? The wider bandwidth and more precise timing hardware required for centimetre-to-decimetre accuracy add cost to both tags and fixed infrastructure compared with simpler RSSI-based systems.

Related reading

• Measurement basics of location systems: distance and direction
• What are radio frequencies and how are they used for indoor location
• Bluetooth Low Energy (BLE) for real-time location
• 2.4 GHz for real-time location