Radio Tuning

When you set up your APs, you might encounter interference, the grouping of several APs in one location. You might also need to change the configured AP channel. The sections that follow show how to manage these settings through both the web browser interface and the CLI.

Note

In this chapter, settings are configured on an Aironet 1130AG AP. Your AP might differ, although this device uses both 2.4- and 5-GHz radios, so you can make the settings on your own devices.

Determining Optimal Channel and Frequency

There are 11 channels available on the 2.4-GHz radio and 23 channels available on the 5-GHz radio. The best settings for the 2.4-GHz radio are channels 1, 6, and 11. This is because these channels do not overlap and provide the best performance. Because of this, you can configure three APs to work in the same environment and not interfere with each other. However, keep the APs at least 5 feet apart. Even on different channels, the broadcasting APs can still interfere with one another.

Bandwidth for the 5-GHz radio, on the other hand, overlaps slightly. You can lessen the impact of this overlap, however, by selecting channels that are not adjacent to each other for neighboring APs.

Tuning to the Optimal Channel and Frequency

When first powered up, Cisco APs scan the airwaves and use the Least Congested Frequency setting for channel selection. That is, the AP listens to the airwaves, and then selects the channel with the least amount of traffic on it. To configure the radio to your own settings, select the Settings tab from the web interface, as shown in Figure 11-2.

Figure 11-2. The Settings Tab Is Home to Various Radio Settings

Scroll farther down this page and you can find the settings for channel and frequency settings as illustrated in Figure 11-3. Select the channels and frequencies you wish from the Least Congested Channel Search list, and then click Apply at the bottom of the screen.

Figure 11-3. Setting Channel and Frequency Values on the Settings Tab

Table 11-4 lists and describes the commands to configure the channel and frequency settings if you elect to use the CLI instead of the web interface.

Table 11-4. Configuring Channels

Command	Description
configure terminal	Enters global configuration mode.
interface dot11radio {0 | 1}	Enters configuration mode for the radio interface. The 2.4-GHz radio is radio 0, and the 5-GHz radio is radio 1.
channel frequency | least-congested	Establishes the default channel. If you enter least-congested, you select the least congested channel available. The following are the channels and frequencies for the 2.4-GHz radio: Channel 12412 Channel 22417 Channel 32422
	Channel 42427 Channel 52432 Channel 62437 Channel 72442 Channel 82447 Channel 92452 Channel 102457 Channel 112462 Channel 122467 (EMEA and Japan only) Channel 132472 (EMEA and Japan only) Channel 142484 (Japan only and only for 802.11b) The following are the channels and frequencies for the 5-GHz radio: Channel 345170 (Japan only) Channel 365180 Channel 385190 (Japan only) Channel 405200 Channel 425210 (Japan only) Channel 445220 Channel 465230 (Japan only) Channel 485240 Channel 525260 Channel 565280 Channel 605300 Channel 645320 Channel 1005500 Channel 1045520 Channel 1085540 Channel 1125560 Channel 1165580 Channel 1205600 Channel 1245620 Channel 1285640
	Channel 1325660 Channel 1365680 Channel 1405700 Channel 1495745 Channel 1535765 Channel 1575785 Channel 1615805
end	Returns to privileged EXEC mode.

Note

The WLSE can also set channels. Also, a controller-based solution can automatically assign channels. Again, WLSE was examined in Chapter 10, "CiscoWorks Wireless LAN Management Solution Engine."