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 in Windows 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 actual PHY rate at which the
client was connected to the AP during an active survey. This is
unlike the Expected PHY
Rate available for
passive surveys, where the PHY rate is not measured, but rather
estimated based on the signal level. 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 used.
The PHY rate that is measured
is the rate at which the adapter is connected to the AP at any
given spot along the survey path. As you move along the path, the
adapter typically roams to the AP that provides the strongest
signal within your WLAN.
It is important to remember
that some adapters let you adjust roaming thresholds; these roaming
settings might affect the roaming behavior and, therefore, the
measured PHY rate. For example, consider two APs located 20 meters
away from each other with the signal level ranging from -30 dBm
next to the APs to -70 dBm in the middle of the distance between
the APs. As you walk from the first to the second AP, some clients
will roam as soon they pass the middle point, while others will not
roam until they are only a few meters away from the second AP. For
this reason, the PHY rate visualization is heavily dependent upon
one's walkabout path and its direction. Walking from the first to
the second AP might produce a picture that would be different from
the one produced by walking in the opposite direction.
Double-clicking on the Actual
PHY rate legend on the status bar allows you to configure the color
scheme and change its value range.
When low actual PHY rate areas
are discovered, the following solutions are suggested:
that the set of supported rates and standards of the adapter being
used for active surveys is at least as good as that of the
rates might be caused by non-aggressive roaming. Check the adapter
roaming settings and repeat the survey in the questionable zones.
Try to walk very slowly to give the adapter time to roam and
establish a good quality link to the AP.
||Increase the signal level, as it is
directly related to the PHY rate. See the suggested solutions for
increasing signal level in the
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.
are using legacy 802.11 a/b/g equipment, consider upgrading to
802.11n or 802.11ac.