The physical layer (PHY) rate is the speed at which client devices
communicate with the AP. When you move a computer connected to the
AP within the WLAN coverage area, the adapter properties dialog on
Windows or the Wi-Fi icon menu on macOS displays the varying
connection speed, which may be as high as 450 or 300 Mbps when you
are close to the AP or as low as 1 Mbps when you are 50 meters away
from it. The displayed speed is the PHY rate.
The PHY rate directly affects the throughput rate, which is the
average speed at which the client and AP can exchange
application-level data, such as files. The throughput rate is
always lower than the PHY rate, typically by more than 50%, due to
a number of factors, such as protocol overheads and
retransmissions. A low PHY rate always means low data throughput
and therefore poor WLAN performance.
The PHY rate is shown for the AP that has the strongest signal in
the given map area among the APs selected for analysis. This mimics
the roaming behavior of client adapters that connected to the
strongest AP. While other audible APs may offer higher PHY rates, a
typical adapter will connect to the AP with the strongest signal.
You can deselect one or several of the selected APs to see PHY rate
values for less strong APs.
Expected PHY rate calculations are based on signal strength and use
a table that maps signal levels to PHY data rates. The table uses
average values for common adapter types. The actual PHY rate that
you observe may be lower or higher than the expected rate,
depending on the specific adapter and AP equipment being
Double-clicking on the Expected PHY rate legend on the status bar
allows you to configure the color scheme.
When low expected PHY rate areas are discovered, the following
solutions are suggested:
Increase the signal level, as it is directly related to the PHY
rate. See the suggested solutions for increasing signal level in
the Signal Level
Check your AP capabilities. If you are using newer 802.11n
equipment, make sure that the maximum MCS indices, Short GI, and 40
MHz channel bandwidth are allowed in the device configuration.
Check your Client Capabilities settings. You might have
erroneously limited them too much.
If you are using legacy 802.11 a/b/g equipment, consider upgrading
to 802.11n or 802.11ac.