Multipath Simulator
Drag an access point and a client around a room to see how reflections off the walls add up or cancel, and why a few centimetres can change the signal by 20 dB.
How to use this tool controls and what to look for
Drag the access point and the client around the room and watch the reflected paths add up or cancel at the client.
Controls to change
- Walls: make the walls reflect more (metal) or less (drywall, glass).
- Reflections: go from None to Up to 3 bounces.
- Band: compare 2.4, 5 and 6 GHz.
- Block the direct path: remove line of sight, so only reflections reach the client.
- Across the channel: pick a 20 to 160 MHz channel and see how fading changes across it.
- MIMO: switch to 2×2 and try MRC at the client and Beamforming at the AP.
What to look for
- Move the client a few centimetres and the signal can swing by 20 dB: those dips are multipath fades.
- Across a wide channel some subcarriers fade while others don't. OFDM copes by spreading data across many subcarriers.
- With two antennas the fades rarely line up, so MRC fills in the dips.
- With 2×2 MIMO, rich multipath is what lets two streams be sent at once.
About this tool
Indoors, Wi-Fi reaches a device by many paths at once: straight from the access point and bounced off every wall. The copies arrive with different delays and phases, and add up or cancel out. Drag the access point and the client to see what that does to the signal, across the channel and with two antennas on each side.
What you'll learn
- Why moving a few centimetres can change the signal strength (fading)
- Why fading differs across one channel, and how OFDM copes with it
- How MIMO uses multipath to send several streams at once
- How each path's length, delay and phase are worked out
Common questions
What is multipath in Wi-Fi?
The signal reaching a device by several routes at once, direct and reflected. The copies arrive at slightly different times and add up or cancel depending on their phase.
Why does the signal change when I move a little?
Paths that add up at one spot can cancel a few centimetres away: half a wavelength is about 6 cm at 2.4 GHz and 3 cm at 5 GHz.
Is multipath good or bad for Wi-Fi?
Both. It causes fading on single-antenna links, but MIMO takes advantage of the different paths to send several spatial streams at once.
Free for private and educational use. This interactive model is a simplified teaching aid and may contain mistakes. It is provided as is, without warranty. Use it to understand the concepts, not as a substitute for a site survey, vendor documentation or professional design advice.