Cisco WAP551 Administration Manual page 92

Wireless
Radio
STEP 4
Cisco Small Business WAP551 and WAP561 Wireless-N Access Point
Each mode offers a number of channels, depending on how the spectrum is licensed by
national and transnational authorities such as the Federal Communications Commission
(FCC) or the International Telecommunication Union (ITU-R).
In the Advanced Settings area, configure these settings:
• Short Guard Interval Supported—This field is available only if the selected radio mode
includes 802.11n.
The guard interval is the dead time, in nanoseconds, between OFDM symbols. The
guard interval prevents Inter-Symbol and Inter-Carrier Interference (ISI, ICI). The
802.11n mode allows for a reduction in this guard interval from the a and g definition
of 800 nanoseconds to 400 nanoseconds. Reducing the guard interval can yield a 10
percent improvement in data throughput.
The client with which the WAP device is communicating must also support the short
guard interval.
Select one of these options:
- Yes—The WAP device transmits data using a 400-nanosecond guard Interval when
communicating with clients that also support the short guard interval. Yes is the
default selection.
- No—The WAP device transmits data using an 800-nanosecond guard interval.
• Protection—The protection feature contains rules to guarantee that 802.11
transmissions do not cause interference with legacy stations or applications. By default,
protection is enabled (Auto). With protection enabled, protection is invoked if legacy
devices are within range of the WAP device.
You can disable protection (Off); however, legacy clients or WAP devices within range
can be affected by 802.11n transmissions. Protection is also available when the mode is
802.11b/g. When protection is enabled in this mode, it protects 802.11b clients and
WAP devices from 802.11g transmissions.
This setting does not affect the ability of the client to associate with the WAP
NOTE
device.
• Beacon Interval—The interval between the transmission of beacon frames. The WAP
device transmits these at regular intervals to announce the existence of the wireless
network. The default behavior is to send a beacon frame once every 100 milliseconds
(or 10 per second).
Enter an integer from 20 to 2000 milliseconds. The default is 100 milliseconds.
• DTIM Period—The Delivery Traffic Information Map (DTIM) period. Enter an integer
from 1 to 255 beacons. The default is 2 beacons.
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