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Cisco 3900 Series, Cisco 2900 Series, and Cisco 1900 Series Integrated Services Routers Generation 2 Software Configuration Guide
Chapter Configuring Radio Settings
Configuring Radio Channel Settings
Configuring Radio Channel Settings
The default channel setting for the wireless device radios is least congested. At startup, the wireless
device scans for and selects the least-congested channel. For the most consistent performance after a site
survey, however, we recommend that you assign a static channel setting for each access point. The
channel settings on the wireless device correspond to the frequencies available in your regulatory
domain. See the hardware installation guide for the access point for the frequencies allowed in your
domain.
Each 2.4-GHz channel covers 22 MHz. Because the bands for channels 1, 6, and 11 do not overlap, you
can set up multiple access points in the same vicinity without causing interference. The 802.11b and
802.11g 2.4-GHz radios use the same channels and frequencies.
The 5-GHz radio operates on 8 channels from 5180 to 5320 MHz, up to 27 channels from 5170 to
5850 MHz depending on regulatory domain. Each channel covers 20 MHz, and the bands for the
channels overlap slightly. For best performance, use channels that are not adjacent (use channels 44 and
46, for example) for radios that are close to each other.
Caution The presence of too many access points in the same vicinity can create radio congestion that can reduce
throughput. A careful site survey can determine the best placement of access points for maximum radio
coverage and throughput.
802.11n Channel Widths
The 802.11n standard allows both 20-MHz and 40-Mhz channel widths consisting of two contiguous
non-overlapping channels (for example, 2.4-GHz channels 1 and 6).
One of the 20-MHz channels is called the control channel. Legacy clients and 20-MHz high-throughput
clients use the control channel. Only beacons can be sent on this channel. The second 20-MHz channel
is called the extension channel. The 40-MHz stations may use this channel and the control channel
simultaneously.
A 40-MHz channel is specified as a channel and extension, such as 1,1. In this example, the control
channel is channel 1 and the extension channel is above it.
To set the wireless device channel width, follow these steps, beginning in privileged EXEC mode.
SUMMARY STEPS
1. configure terminal
2. interface dot11radio {0 | 1}
3. channel {frequency | least-congested | width [20 | 40-above | 40-below] | dfs}
4. end
5. copy running-config startup-config
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