RFDifference between UWB vs Bluetooth vs Wi-Fi
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Introduction : For decades, indoor wireless technologies were used for two applications viz. data (served by wi-fi) and audio/connectivity (served by bluetooth or BLE). But with the rise of “smart factory” and “digital keys”, a third requirement has emerged for location determination. Let us understand working principle behind these three technologies i.e. Wi-Fi, Bluetooth and UWB for distance calculation before we explore differences between them.
Bluetooth
- This technology is ubiquitous and it is found in every phone and beacon.
- Traditional bluetooth estimates distance using RSSI (Received Signal Strength Indicator). It estimates distance based on amplitude of the RF signal.
Limitations: Signal Strength is easily affected by the environment. There is a problem when you put your phone in your pocket or walk behind the column, the signal drops and bluetooth thinks you already walked 10 meters away. It is good for knowing if you are near, but bad at knowing exactly where you are.
Wi-Fi
- It is mainly designed for high throughput data transfer, not precise ranging.
- Modern Wi-Fi uses Round Trip Time (RTT) to estimate distance.
Limitations: Wi-Fi uses narrowband signal. In indoor environments, these signals bounce off walls and furniture (multipath interference). Because the Wi-Fi pulses are relatively long, the receiver gets confused between the direct signal and the echoes, leading to accuracy errors of 1 to 5 meters.
UWB
- It is mainly designed for micro-location determination.
- UWB measures Time of Flight. It sends extremely short pulses (~ 2 nanoseconds wide) across a massive bandwidth ( > 500 MHz). It measures the exact time it takes for light to travel from the transmitter to the receiver.
Advantages:
- Pulses are very short and hence UWB receiver can easily distinguish sharp direct signal from the later bounced reflections.
- It prevents relay attack on the car which offers security to car owners from thieves.
Comparison between Bluetooth Vs. Wi-Fi Vs. UWB
| Feature | Bluetooth (BLE) | Wi-Fi | UWB |
|---|---|---|---|
| Frequency Band | 2.4 GHz | 2.4 / 5 / 6 GHz | 3.1 to 10.6 GHz |
| Primary Purpose | Low Power Connectivity | High Speed Data | Secure Ranging & Sensing |
| Ranging Technique | Based on RSSI i.e. Signal Strength | Round Trip Time | Time of Flight (ToF) |
| Accuracy | Low (1-5 meters) | Medium (1-5 meters) | High (~10 cm) |
| Reliability | Low (affected by obstacles) | Medium | High (Resists multipath) |
| Security | Low (Prone to relay attacks ) | Medium | High (Cryptographic Timestamp) |
| Co-existence | Struggles with wifi/microwaves | Struggles with other wifi | Excellent (Operates in noise floor) |
| Infrastructure Cost | Very Low Cost (Beacons are installed) | High Cost (Access Points are needed to form network) | Medium Cost (Anchors are installed) |
Summary
Each of these technologies are used for dedicated applications or use cases as follows.
- Use Wi-Fi if you need to move large files or connect to the internet.
- Use Bluetooth if you need cheap and good enough proximity solution such as finding lost keys in a couch cushions.
- Use UWB if you need critical precision and security. For example, Unlocking a car only when the driver is 1 meter away or Tracking a forklift in a metal heavy warehouse where reflections would confuse Wi-Fi or Bluetooth.
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