Brocade Mobility 5181 Access Point Product Reference Guide (Supporting software release 4.4.0.0) - Manual (Page 138)

124 Brocade Mobility 5181 Access Point Product Reference Guide
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Enabling wireless LANs (WLANs)
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4. Refer to the Beacon Settings field to set the radio beacon and DTIM intervals.
5. Refer to the QBSS Load Element Setting field to optionally allow the access point to
communicate channel usage data to associated devices and define the beacon interval used
for channel utilization transmissions. The QBSS load represents the percentage of time the
channel is in use by the access point and its station count. This information is very helpful in
assessing the access point’s overall load on the channel, its availability for additional device
associations and multi media traffic support.
Select the Enable QBSS load element check box (its selected by default) to enable the access
point to communicate channel usage to Clients. Access points with high channel usage may
not be able to process real-time traffic effectively. Therefore, VOIP phones can use the QBSS
value to determine whether a different access point association can provide better wireless
support, since the QBSS network load is reduced as additional access points are added.
If QBSS is enabled, define a QBSS Beacon Interval to define the beacon time (in seconds) the
access point uses to broadcast channel utilization information. This information should be
periodically accessed, as the access point’s network load will fluctuate throughout the day.
6. Configure the Performance field to set the preamble, thresholds values and QoS values for the
radio.
Beacon Interval The beacon interval controls the performance of power save stations. A
small interval may make power save stations more responsive, but it will
also cause them to consume more battery power. A large interval makes
power save stations less responsive, but could increase power savings. The
default is 100. Avoid changing this parameter as it can adversely affect
performance.
DTIM Interval The DTIM interval defines how often broadcast frames are delivered for
each of the four access point BSSIDs. If a system has an abundance of
broadcast traffic and it needs to be delivered quickly, Brocade recommends
decreasing the DTIM interval for that specific BSSID. However, decreasing
the DTIM interval decreases the battery life on power save stations. The
default is 10 for each BSSID. Brocade recommends using the default value
unless qualified to understand the performance risks of changing it.
Support Short Preamble The preamble is approximately 8 bytes of packet header generated by the
Mobility 5181 Access Point and attached to the packet prior to transmission
from the 802.11b radio. The preamble length for 802.11b transmissions is
data rate dependant. The short preamble is 50% shorter than the long
preamble. Leave the check box unselected if in a mixed Client/AP
environment, as Clients and the Mobility 5181 Access Point are required to
have the same RF Preamble settings for interoperability. The default is
Disabled. The preamble length for 802.11a and 802.11g transmissions is
the same, with no long or short preamble lengths.