# We use Wi-Fi every day to connect our devices to the internet, but how does it actually work? How do our devices communicate with the router and what makes Wi-Fi different from other types of wireless communication?
In: Technology
Giga ELI5:
Imagine you go camping with a friend. You get separated and lost.
Night falls, and trying to get better bearings, you climb on a mountain. There’s mountain in the distance and you can see your friend on top of it. You yell, but they can’t hear you. But, they can vaguely see you. That’s why radio masts are put up somewhere high.
You need to plan how to come down and decide where to meet. But it’s dark and there’s forest in the valley, so it’s impossible to find each other unless you very clearly agree at which point of the valley you’re going to meet.
Luckily, you have a flashlight. You can pick out a big tree or rock in the valley and point flashlight at this. “Let’s meet there”. You’re both out of water, so you also point at the river flowing through the valley: “Get water!”. And maybe pile of dead trees at the edge of the valley “Get firewood!”. Your friend waves (acknowledges). They understood the message.
You’ve compiled your message into a packet, and submitted it over visible light (a spectrum of electromagnetic wave). Wifi does basically same with network data, and transfers it over EM, but as radio waves. That’s also electromagnetic wave spectrum, but much lower frequency. And you got a response (acknowledgement signal or ACK).
Maybe there’s third and fourth mountain, and two hikers in exactly similar trouble. But their flashlight is blue. So your friend gets your packet and ignores theirs. That’s how radio channels/different frequencies work, and authentication of signals, so devices know what to respond to and what to ignore. Also, each mountain is like an IP address/device ID to a particular hiker you’re trying to communicate with.
Maybe, at the start of your packet, you point flashlight at yourself. So you’re sending identifier at the header (start) of your packet. That’s why in ordinary radio communication, it’s common to repeat your own callsign three times before message.
Maybe you repeat your message three times, to make sure your friend noticed every area you pointed at. Or lead your flashlight slowly from one hotspot to another. If they miss a bit each time, they can still likely put together the whole packet out of repetitions. That’s vaguely how error correction works.
And so on. Almost everything about WiFi can fit into this imaginary scenario. And nearly everything uses EM, from radars to radio to satellite TV to cellphones. WiFi is just a protocol about how this particular method works (what you do with the flashlight). In different scenario (protocol), your friend could understand morse code, so you could type your message by blinking the flashlight at them. Or something else entirely different. Maybe you have bunch of colorful flags with meaning, and you shine flashlight at them, and your friend gets it (ships used flags to communicate) down to simple streetlights on road (green means “go”). Or write your message on a cardboard and shine light at it. Various devices use various methods.
As for 4G/5G, that people tend to get confused about, that’s more about what sort of flashlight you have. Maybe it’s super bright – so it’s very visible, but not precise, maybe it has a narrow and strong beam – thus precise, but not well seen unless you know where to look, maybe there’s dedicated blinking button for morse code, etc. Or maybe it has three separately rotating heads, so you can point at all three locations at once (veeery vaguely, multiplexing)
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