Physics

Wi-Fi in a House

Maxwell's equations solved on the GPU over a whole house at the true wavelength, 12.5 cm at 2.4 GHz and 6 cm at 5 GHz. Watch the router's wave spill through doorways, bounce off walls and leave dead spots a few centimetres across, then switch to the signal map to see which rooms a phone can still stream from, and why 5 GHz is faster but fades sooner.

routerphonemesh node−67 dBm: video calls−80 dBm: barely connects

Drag the router, the phone or the mesh node · click the floor to put the phone there · drag empty space to orbit · scroll to zoom

Signal at the phone—

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Show

Band

Walls

Router power 20 dBm

14 dBm23 dBm

Mesh nodeSmooth like a phoneClose the inner doors

Camera

Phone

signal—

at one point—

multi-wall model—

link rate—

SNR—

to the router—

walls in the way—

Simulation

grid—

cell—

simulated time—

steps / frame—

frame rate—

JS per frame—

What to observe

Put the phone on the far bed of the brick house. At 2.4 GHz it holds on; at 5 GHz every wall costs more and it falls to Poor. On the sofa it is the other way round: 867 Mbit/s at 5 GHz against 144.
Echoes from the walls interfere into standing waves, with dead spots λ/2 apart: 6 cm at 2.4 GHz, 3 cm at 5 GHz. A hand's width can change the reading at one point by 10 dB; a phone's antenna averages over a few cm.
The metal fridge reflects almost everything, so it casts a radio shadow that only echoes from the kitchen walls fill in.
In the concrete house 5 GHz reaches the bedroom only at Poor. A mesh node in the hall, in sight of the bedroom door, lifts it to Good: the phone joins whichever node is stronger.

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