Wi-Fi does not operate at one fixed speed.
The router and connected device continuously adjust how data is encoded and transmitted according to current connection conditions. These combinations are commonly described through a modulation and coding scheme, or MCS.
Higher MCS levels can carry more information in the same amount of time. However, they also require a stronger and cleaner connection to be decoded correctly.
When a device moves farther from the router and connection quality declines, the Wi-Fi link may switch to a more robust transmission mode. That mode is easier to receive reliably, but it transfers less data in the same amount of airtime.
In practical terms:
- A strong connection can use faster and more efficient transmission modes.
- A weaker connection may need slower and more conservative modes.
- A device can therefore remain connected even while its available speed falls significantly.
MCS is determined by factors including the modulation method and error-correction coding rate. Wi-Fi connection speed is also influenced by channel width, the number of spatial streams, and guard interval.
This automatic adjustment is not a fault. It allows Wi-Fi devices to maintain a connection under less favorable conditions instead of disconnecting immediately.