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What Is Bluetooth and How Is It Different From Wi-Fi?
Bluetooth is a short-range wireless standard for connecting nearby devices. Learn about Classic and Low Energy, the 2.4 GHz band it shares with Wi-Fi, and its limits.
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Quick answer
Bluetooth is a short-range radio standard for linking nearby devices such as headphones, speakers, keyboards and sensors. It has two radio options, Bluetooth Classic for continuous streams like audio and Bluetooth Low Energy for small, infrequent data at very low power. Unlike Wi-Fi, it is not designed to connect you to the internet.
What Bluetooth is for
Bluetooth replaces cables between devices that are close to each other. The Bluetooth Special Interest Group, which maintains the standard, offers two radio options for different kinds of wireless connectivity: Bluetooth Classic and Bluetooth Low Energy (LE). Both operate in the 2.4 GHz ISM band, using the frequencies from 2.402 to 2.480 GHz, and both use frequency-hopping spread spectrum, which means the radio rapidly changes channel during a connection to reduce the effect of interference.
A wireless headset, a game controller, a fitness tracker, a car hands-free system and a door sensor all use Bluetooth because they need a nearby, low-power link rather than a high-capacity connection to a network.
Classic and Low Energy
| Criteria | Bluetooth Classic | Bluetooth Low Energy |
|---|---|---|
| Channels | 79 channels, 1 MHz apart | 40 channels, 2 MHz apart |
| Data rates | 1 Mb/s, with 2 and 3 Mb/s in enhanced mode | 125 kb/s up to 2 Mb/s depending on the mode |
| Topology | Point-to-point, including small piconets | Point-to-point, broadcast and mesh |
| Typical use | Streaming audio and transferring data | Low-power sensors, beacons, wearables and location features |
Classic suits a steady stream, which is why it is used for audio to speakers, headphones and car systems. Low Energy was designed for very low power operation, so a small battery can last a long time in a sensor that sends a few bytes at a time. Low Energy also supports positioning features, including presence detection through advertising, direction finding and distance estimation.
How it differs from Wi-Fi
Wi-Fi and Bluetooth share the same crowded radio neighbourhood but do different jobs. Cisco describes Wi-Fi as wireless networking that connects devices to a local network and typically onwards to the internet. Bluetooth links individual devices directly to each other.
| Question | Bluetooth | Wi-Fi |
|---|---|---|
| Main job | Connect nearby accessories and sensors | Connect devices to a local network and the internet |
| Power use | Designed to be low, especially in Low Energy | Generally higher for the same device |
| Typical data volume | Audio streams and small messages | Video, large downloads, many devices at once |
| Needs a router or access point | No, devices pair directly | Normally yes |
Sharing the 2.4 GHz band
Because Bluetooth and the 2.4 GHz Wi-Fi band occupy the same part of the spectrum, a busy 2.4 GHz network can affect Bluetooth audio, and heavy Bluetooth use can in turn affect nearby 2.4 GHz Wi-Fi. Frequency hopping helps Bluetooth avoid persistent interference. If a headset stutters near a router, moving the router to 5 GHz for devices that support it, as discussed in 2.4 GHz vs 5 GHz Wi-Fi, can reduce the crowding.
What the standard does not promise
The Bluetooth SIG's overview lists transmit power limits of up to 100 mW (20 dBm) and regulatory limits that products must respect, but it gives no single range figure in metres. Real range depends on the power class of the product, the antenna, walls, bodies and interference. A figure on a package describes ideal conditions rather than the experience in a crowded room.
The latest Low Energy features include a method called Channel Sounding, which the SIG describes as bringing true distance awareness to connected devices, which can make features such as unlocking a nearby device more reliable.
Pairing and everyday troubleshooting
Two Bluetooth devices normally need to be paired once so that they recognise each other afterwards. If a device will not connect, the usual causes are that it is already connected to another phone or computer, that it is not in pairing mode, or that an old pairing record is stale. Removing the device from the list and pairing again resolves many cases. Keeping the devices close and away from other 2.4 GHz equipment removes most of the rest.
Bluetooth is not the internet
A phone connected to a Bluetooth speaker is not thereby online. Internet access still arrives over Wi-Fi or a mobile network; Bluetooth only carries the link to the accessory.
Sources
- Bluetooth Technology Overview — Bluetooth SIG
- What Is Wi-Fi? — Cisco
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