Cisco WAP131 Administration Manual page 76

Wireless
Radio
STEP 5
Cisco WAP131 and WAP351 Administration Guide
referred to as the primary and secondary channels. The primary channel is
used for 802.11n clients that support only a 20-MHz channel bandwidth and
for legacy clients.
Choose one of these options:
- Upper—Sets the primary channel as the upper 20-MHz channel in the
40-MHz band.
- Lower—Sets the primary channel as the lower 20-MHz channel in the
40-MHz band. Lower is the default selection.
• Channel—The portion of the radio spectrum that the radio uses for
transmitting and receiving.
The range of available channels is determined by the mode of the radio
interface and the country code setting. If you select Auto for the channel
setting, the WAP device scans available channels and selects a channel
where the least amount of traffic is detected.
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 parameters:
• 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.
Choose 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. This is the default selection.
- No—The WAP device transmits data using an 800-nanosecond guard
interval.
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