# How WiFi Sends Data How a Wi\-Fi router turns data into radio waves, from shaking charges in an antenna to bits recovered by a laptop\. Shows how the signal's shape carries information\. By nimble\-koala\-17a11a31 Topic: Computing, AI & Electronics [Open the interactive Jig](https://ask.jig.com/j/8q4wFq23b8lt) ## Transcript ### 1. Invisible light Wi\-Fi sends your data as radio waves: the same kind of electromagnetic wave as light, only far too long for eyes to see\. They cross the room at about 300,000 km per second\. The glowing rings are a picture\. Real radio waves are invisible\. ### 2. Shaking charges Inside the router, an electric current rushes back and forth through a small metal antenna billions of times a second\. That shaking launches a wave that spreads out mostly sideways, like a doughnut, and only weakly off the tip\. The black rod is a cover\. The copper that radiates inside it is only a few centimetres long\. ### 3. A wave 12\.5 cm long Wi\-Fi rides on a carrier wave at 2\.4, 5 or 6 GHz\. At 2\.4 GHz the crests are 12\.5 cm apart; at 5 GHz only about 6 cm\. Switch bands and compare\. Higher frequency is not faster, the crests are just closer\. Drawn to scale across the desk, but slowed down billions of times\. ### 4. Bits become shapes A steady wave says nothing\. To send bits, the radio sets the wave's height and timing, its amplitude and phase, to one of an agreed set of shapes\. Each dot on the map is one shape; the wave changes shape for every new symbol\. 4 dots carry 2 bits per symbol, 16 dots 4 bits, 64 dots 6 bits\. Wi\-Fi 6 can use 1024 dots, 10 bits, on a clean signal\. ### 5. Many waves at once Instead of one fast wave, Wi\-Fi sends many slow sub\-waves side by side, each carrying its own symbol\. A classic 20 MHz channel uses 52 of them\. They are spaced so exactly that they do not disturb each other, then added into one signal\. This is called OFDM\. A classic symbol lasts 3\.2 microseconds, plus a 0\.8 microsecond guard\. ### 6. Echoes in the room Waves bounce off walls, desks and furniture, so copies of the signal arrive by several paths, a few billionths of a second apart\. A short guard time before each symbol lets these echoes fade so they do not blur the next one\. 2\.4 GHz gets through walls more easily; 5 GHz carries more data but reaches less far\. ### 7. Taking turns Every device on a channel shares the same air, so a radio listens first and talks only when it is quiet\. Press Send, or click the router: it listens, sends a data frame, and the laptop answers with a short acknowledgement\. No acknowledgement? The sender waits a random moment and tries again\. ### 8. Back to bits The laptop's antennas, hidden in the lid, turn the faint wave back into a tiny current\. Its radio separates the sub\-waves, reads each one's shape, fixes errors and recovers the original bits, many millions per second\. Wi\-Fi is only the last hop\. The router passes your data on through a cable to the internet\.