Brocade Mobility 7131N-FGR Access Point Product Reference Guide (Supporting software release 4.0.0.0-35GRN and later) - Manual (Page 159)

Brocade Mobility 7131N-FGR Product Reference Guide 147
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Enabling Wireless LANs (WLANs)
5
4. Configure the Performance field to set the preamble, thresholds values and QoS values for the
radio.
Support Short
Preamble The preamble is approximately 8 bytes of packet header
generated by the access point and attached to a packet prior to
transmission from the 802.11b radio. The preamble length for
802.11b transmissions is rate dependant. A short preamble is
50% shorter than a long preamble. Leave the checkbox
unselected if in a mixed MU/AP environment, as MUs and the
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.