How do bluetooth and wifi work?
This is a great question! We all use bluetooth and Wi-Fi everyday, but how do they actually work? They are more similar than you may think, and you’ll be surprised to find out just how many other devices use similar technology.
Bluetooth speakers, along with other types of devices like microwaves, baby monitors, car alarms, and Wi-Fi operate using ultra-high frequency radio waves in a range between 2.400 and 2.4835 gigahertz (GHz). This has been set aside by the international agreement for the use of industrial, scientific and medical devices. Radio waves are part of the electromagnetic spectrum, just like visible light, infrared, and X-rays. They can be created by passing electricity through an antenna as shown in the figure below. Radio wavelengths are very long, much longer than the width of an atom which means they are invisible to humans and can pass through objects like walls and furniture unobstructed. This is why you can maintain a connection even if your two devices are in separate rooms.
If you want a quick recap from trigonometry, frequency is how many wave peaks occur per second and wavelength is the distance between two peaks. All waves travel at the speed of light, so frequency and wavelength are related—we can always get one from the other.
Your electronic devices contain an antenna that can both send and receive radio waves and differentiate between tiny changes in frequency. Just as your eyes can tell the difference between 545 terahertz (THz) green light and 430 THz red light, the antenna in your bluetooth device can tell the difference between 2.477 GHz light which it interprets as a 1, and 2.417 GHz light it reads as 0. Your phone can switch between emitting different frequencies 60 million times per minute which means it can send 1 million 1s and 0s every second!
A computer chip in your devices receives all of these 1s and 0s and can transform them into the audio you hear. Everything is sent in bursts called packets. Each packet consists of an access code, a header, and a payload. The access code synchronizes your devices and ensures that information is being transmitted to the correct device. The header contains basic information about the size of the package. Finally, the payload, which can vary in size, but is the largest portion of the package and contains your audio. The computer chip in your speaker is programmed to convert this data into sound.
Bluetooth is two-way data transmission, meaning that both your audio playing device and your speaker send packets. For instance, your speaker can send pause, play, or skip forward commands to your audio playing device. To pair, typically both devices must be activated and “discoverable,” broadcasting information about themselves. While some devices are always discoverable, others require a pairing mode for activation. Once paired, both devices agree on two specific frequencies in the 2.4 to 2.4835 GHz range which will represent a 1 or 0. This is a fairly wide range, so even if there are multiple bluetooth devices operating in the same room at the same time you won’t have interference.
If you’re happy with this explanation of bluetooth, you can stop reading here. In the upcoming section, I cover more of the technical details about adaptive frequency hopping.
The 2.4 to 2.4835 GHz radio wave range used by bluetooth devices to communicate is divided into 79 different channels. Each channel has a different set of 2 frequencies that represent a 1 or a 0. There are so many channels to limit the amount of interference between all of the different devices that operate within this range.
Previously, I simplified the concept of device connection as if your devices choose one specific channel, with one frequency for 1 and another for 0. This is not totally accurate. What actually happens is your devices change channels 1600 times a second. That means every 1/1600 of a second, two new frequencies are used to send and receive data.
The order is dictated by the device playing audio, and is agreed upon when the devices pair. If a channel is noisy, which often occurs from overuse or interference at that time, your devices will adapt and not broadcast over that band. This adds an additional level of security, since anyone trying to listen won’t know the channel sequence. It also helps to further limit the amount of interference between bluetooth devices.
Every time the channel changes, a packet of data is sent either from your speaker or your device, which alternate sending and receiving data. This same process happens when you connect to Wi-Fi, although only over 14 channels.
What is Wi-fi?
Every line in the image above is an internet cable which connects computers around the world. Of course, there are just as many cables on land as well. This “world-wide-web” of wires means that any connected computer can communicate with any other connected device, anywhere in the world. This is the internet. How it all works is incredibly fascinating, but is unfortunately not covered in this article. If you want to learn more, you could submit a “Quirky Query” of your own to the Google form on JOLT’s instagram page!
Wi-fi stands for Wireless Fidelity and allows you to connect to the internet without the need for a physical wire (ethernet cable). When your computer is connected to Wi-Fi it sends out radio waves to a wireless router which is connected to the internet by an ethernet cable. This connection is very similar to bluetooth, they even use the same 2.4 GHz frequency, but with some key differences.
Wi-Fi uses stronger radio waves with a larger amplitude so that waves suffer less interference and can propagate farther. This is why you may notice that Wi-Fi has a much longer range than bluetooth. Wi-Fi can also transmit 54 times as much information, again all in the form of 1s and 0s. The exact process of how your router converts this into an internet traffic request is beyond the scope of this article. Finally, if you’ve ever noticed your connection vastly improves from just moving closer to the router, this is because Wi-Fi can switch from the 2.4 to a 5.8 GHz frequency band to transmit a larger amount of data but only over shorter distances.
Both bluetooth and Wi-Fi are incredibly complex ways of transmitting data. I didn’t even touch on how signals are analyzed and turned into a sound file or website, never mind the advanced circuitry and hardware involved in this process. I merely covered the very basics of how radio waves can be used to send messages. I hope you enjoyed this article, and keep asking quirky queries!
Source: Britannica
This article was edited by Maya Cheam and August Muller.
