How Wi-Fi turns radio waves into data

Wi-Fi feels invisible, but it is ordinary radio: the same kind of electromagnetic wave that carries a broadcast station, tuned to carry data instead of music. Your router and your phone take turns shaping radio waves, and every tiny change in those waves stands for bits.

Step 1: Pick a band and a channel

Wi-Fi uses unlicensed radio bands at 2.4 GHz and 5 GHz, plus 6 GHz on Wi-Fi 6E and Wi-Fi 7 devices where regulators allow it. Each band is divided into channels, slices of spectrum a network can claim.

• 2.4 GHz reaches farther and passes through walls better, but it is crowded and slower.
• 5 GHz carries more data over shorter distances.
• 6 GHz offers wide, uncrowded channels that work best in the same room or the next one.

Step 2: Turn bits into waves

A radio wave has properties a transmitter can change very precisely, including its amplitude (how strong it is) and its phase (where it is in its cycle). Wi-Fi uses QAM, quadrature amplitude modulation, which varies both at once. Each distinct combination of amplitude and phase is called a symbol, and each symbol stands for a group of bits.

With 16-QAM there are 16 possible symbols, so each one carries 4 bits. Wi-Fi 6 supports 1024-QAM, or 10 bits per symbol, and Wi-Fi 7 goes up to 4096-QAM, or 12 bits. Denser patterns carry more data but need a cleaner signal, which is why your speed drops as you walk away from the router.

Step 3: Split the channel into subcarriers

One fast stream on a single frequency breaks down easily indoors, because signals bounce off walls and arrive at slightly different times. So Wi-Fi uses OFDM, orthogonal frequency-division multiplexing. It divides each channel into many narrow subcarriers, each carrying its own slower stream of QAM symbols, side by side. If interference hits a few subcarriers, error-correcting codes added to the data let the receiver repair the damage.

Wi-Fi 6 goes further with OFDMA, handing different groups of subcarriers to different devices at the same moment. Routers with several antennas can also send multiple streams in parallel, a technique called MIMO.

Step 4: Receive, check and take turns

Your phone's antenna picks up the wave, measures the amplitude and phase on every subcarrier, maps each symbol back to bits and reassembles the packet. It checks the packet for errors and sends a short acknowledgment. Because every nearby device shares the same air, Wi-Fi listens before it talks: a device waits until the channel is quiet before transmitting, so its signal does not collide with someone else's.

Why it matters

This explains everyday Wi-Fi behavior. Speeds fall with distance because the router switches to simpler, sturdier symbols. Apartment buildings feel slow on 2.4 GHz because dozens of networks share only a few non-overlapping channels. And moving the router out of a cabinet, or joining the 5 or 6 GHz network when you are close by, often helps more than paying for a faster plan.