What is Bluetooth and how does it work?

You probably use Bluetooth every day, whether to sync listeners with your smartphone or transfer a few files from one device to another. But what is Bluetooth anyway, why is it called that and how does it work?

We’ll break down some of the big ideas behind this technology so you can learn more about Bluetooth.

What is Bluetooth?

To explain it in the simplest possible way, Bluetooth is a wireless communication standard that uses radio waves to transmit data between devices. However, many wireless communication standards use the same technique, so what makes Bluetooth different? Unlike other forms of radio communication, Bluetooth waves do not travel very far and constantly change frequency.

The constant frequency switching used by Bluetooth is known as Frequency Hopping Spectrum. This technology makes Bluetooth highly secure because the signals are resistant to interference, difficult to intercept by third parties and difficult to jam. Moreover, they can coexist with conventional signals without the two interfering. This technology was invented by a few different people throughout history, but a notable contribution came from Hollywood actress Hedy Lamarr and composer George Antheil in the 1940s.

You can only use Bluetooth within a short range, with newer versions reaching a range of around 240m (800ft). Walls, ceilings and other obstacles can further reduce this range. But that’s part of the appeal of Bluetooth, as many devices can exist in close proximity and likely won’t conflict with each other.

The foundations of Bluetooth date back to 1989 at the Swedish telecommunications company Ericsson. Nils Rydbeck and Johan Ullman asked engineers Jaap Haartsen and Sven Mattissson to invent a way to connect computers to wireless headsets that the company wanted to introduce to the market.

These designers originally created Bluetooth to replace the old RS-232 telecommunications cable standard from 1960. Between 1994 and 1997, the team created a practical implementation of the concept. In 1998, the Bluetooth Special Interest Group (SIG) was launched and initially consisted of Ericsson, Intel, Nokia, Toshiba and IBM. However, despite this early work, the first consumer device to be released with Bluetooth support was the Ericsson T39 mobile phone in 2001.

The name “Bluetooth” comes from Jim Kardach of Intel, which was part of the first GIS. He was talking to Sven Mattisson about Scandinavian history, especially the novel The long ships by Frans G. Bengtsson, who talks about the Vikings and the 10th century Danish king Harald Bluetooth. Jim saw a Harald Bluetooth runestone in the book A Viking Story by Gwyn Jones and came up with a name and logo based on it. Kardach chose this name because Bluetooth unites devices, just as Harald Bluetooth united the Danish kingdom. The logo is a combination of two runes which represent the initials of Harald Bluetooth.

As mentioned, Bluetooth uses radio waves. It operates in the 2.402 to 2.480 GHz range, where Wi-Fi and other standards exist. Bluetooth effectively allows devices to create a small network called a piconet. One device is the “central” device, and the others are “peripheral” devices, with eight devices capable of interacting simultaneously – one central device and seven peripheral devices.

The central device coordinates everything and can send data to any device, or request that it send it. Peripheral devices can only talk to the central device and cannot communicate with each other. For a simple example, consider a pair of headphones synced to your smartphone. Your phone is the central device and the headphones are the peripheral device.

Each Bluetooth device has a 48-bit address. However, you usually won’t see it. Instead, you’ll likely see the human-readable names of devices like “Jake’s iPhone” or “Sony WH-1000XM5.”

For two Bluetooth devices to talk to each other, you need to pair them. If you’ve never connected the two devices before, pairing involves several steps:

1. Request: The two devices must discover each other. One device sends a request and another device listens for the requests. They send each other their addresses and names, along with some additional information. For example, taking a pair of true wireless headphones out of their case puts them in pairing mode. You can then find the headphones in your phone’s Bluetooth device list.
2. Paging: The devices will then begin the process of forming a connection. They will exchange more information, after which they will finalize the process.
3. Link: After completing the polling and paging steps, both devices can send and receive data. In the case of our example headphones, you can now listen to music with them from your phone.

As you probably already know, this process only needs to happen once. After that, the devices will remember each other and connect automatically when in range. Devices that can do this are called paired devices.

Devices may require an authentication step to prevent unwanted connections from being established. That’s why you’ll see prompts to enter a PIN or approve a pairing request when syncing two new devices.

Once complete, synced devices can send and receive many types of data. Depending on the type of data, there are several ways to do this. Over the years, Bluetooth has seen new versions, updates, standards and improvements, introduced in versions from Bluetooth 1 to current Bluetooth 5.

You might not realize it, but Bluetooth connects wireless controllers to game consoles and PCs, headphones to smartphones, and so much more. Even though the use case in mind when Bluetooth was created was a telephone headset, the standard continued to be used in all sorts of devices. We are currently in the era of Bluetooth 5 and many Bluetooth 4 devices are still in use today.

It may seem like audio is a natural extension of Bluetooth. After all, the engineers who created it had mobile phone headsets in mind. But this implementation was only intended to achieve intelligible call quality, not the full range of music that people enjoy. This is where Bluetooth audio codecs come in. Eventually, the Bluetooth standard came to include the SBC Bluetooth codec by default, but it’s notorious for not providing the best audio quality. As a result, proprietary codecs have come to fill this niche, including aptX, Sony’s LDAC, and Samsung’s Scalable Audio Codec. Along with Bluetooth 5.0 we got the LC3 codec and LE Audio, which promise to bring many improvements.

With the introduction of version 5.2 in 2020 came the LC3 codec and LE Audio. The latter looks promising for hearing aids, HD voice calls, and more. LE stands for Low Energy, and it was already part of Bluetooth 4, but Bluetooth 5 brought many improvements. It’s technically a different standard, but many devices can support Bluetooth Classic and LE. Bluetooth LE makes it possible to create piconets without a constant central device with peripherals. Instead, it can mesh and broadcast, as well as detect where devices are and how they move.

To simplify, LE is for incidental communication, like fitness trackers and smart home devices, while Classic is for constant communication, like headphones. But LE Audio bridges that gap a bit, allowing for high-quality calls without requiring as much power. Broadcast capability essentially allows Bluetooth 5 LE devices to function as a public address system, which could be useful for quickly broadcasting announcements to large groups of people.

The LC3 codec also has many advantages. It uses less power, so devices can be smaller and last longer. According to preliminary data, it also has much better audio quality than SBC. Just like the SBC codec, it will be offered by default, so all kinds of devices can include it.

Nowadays, you can find Bluetooth in phones, laptops, headphones, smart home devices, and many other things. The standard has come a long way since its initial implementation, and it looks like it will be present in many new devices for a long time.