Why Wireless Speeds Always Change

Dynamic Rate Scaling Changes Wi-Fi Speeds

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Wi-Fi networks support certain maximum connection speeds (data rates) depending on their configuration. However, the maximum speed of a Wi-Fi connection can automatically change over time due to a feature called dynamic rate scaling.

When a device initially connects to a network over Wi-Fi, its rated speed is calculated according to the current signal quality of the connection. If necessary, the connection speed automatically changes over time to maintain a reliable link between the devices.

Wi-Fi dynamic rate scaling extends the range at which wireless devices can connect to each other in return for lower network performance at the longer distances.

802.11b/g/n Dynamic Rate Scaling

An 802.11g wireless device in close proximity to a router will often connect at 54 Mbps. This maximum data rate is displayed in the device's wireless configuration screens.

Other 802.11g devices located further away from the router, or with obstructions in between, may connect at lower rates. As these devices move further away from the router, their rated connection speeds eventually get reduced by the scaling algorithm, while devices that move closer can have speed ratings increased (up to the maximum of 54 Mbps).

Wi-Fi devices have their rates scaled in predefined increments. 802.11ac offers speeds up to 1,000 Mbps (1 Gbps) while 802.11n maxes out at 1/3 that speed, at 300 Mbps.

For 802.11g, the defined ratings are (from highest to lowest):

  • 54 Mbps
  • 48 Mbps
  • 36 Mbps
  • 24 Mbps
  • 18 Mbps
  • 12 Mbps
  • 9 Mbps
  • 6 Mbps

Similarly, old 802.11b devices supported the following ratings:

  • 11 Mbps
  • 5.5 Mbps
  • 2 Mbps
  • 1 Mbps

Controlling Dynamic Rate Scaling

Factors that determine which data rate is dynamically chosen for a Wi-Fi device at any given time include the:

  • distance between the device and other Wi-Fi communication endpoints
  • radio interference in the path of the wireless device
  • physical obstructions in the path of the Wi-Fi device, that also interfere with signal quality
  • the power of the device's Wi-Fi radio transmitter/receiver

Wi-Fi home network equipment always utilizes rate scaling; a network administrator cannot disable this feature.

Other Reasons for Slow Wi-Fi Connections

There are a number of other things that could contribute to slow the internet, not just dynamic rate scaling. This is especially true if your connection is always slow. If boosting the Wi-Fi signal isn't enough, consider making some other changes.

For example, maybe the router's antenna is too small or pointed in the wrong direction, or there are too many devices using Wi-Fi at once. If your house is too large for a single router, you might consider buying a second access point or using a Wi-Fi extender to push the signal further than it could otherwise reach.

Maybe your computer is suffering from outdated or incorrect device drivers that are limiting how fast it can download or upload data. Update those drivers to see if that fixes the slow Wi-Fi connection.

Something else to remember is that you can only get Wi-Fi speeds as fast as what you're paying for, and it's completely independent of the hardware you're using.

If you have a router that's capable of 300 Mbps and no other devices connected, but you're still not getting more than 8 Mbps, it's likely due to the fact that you're only paying your ISP for 8 Mbps.