Manual Channel Setting on 3802e wireless router

[dedrick]

Hello.  I'm doing some WiFi client testing in the 5GHz DFS-required bands.  I'm thinking about buying a 3802e wireless router for this experiment, but before I do, can someone tell me if this model will allow me to manually set 40MHz channel width and manually set to channels 54, 62, 102, 110, 118, 126, 134, or 142 ?  Thanks in advance.

[Rasika Nayanajith]

Yes, you are able to set channel statically.

But important to decide how you manage this AP ? Typically one would use WLC (Wireless LAN controller) to manage Cisco APs.

Refer this deployment guide

http://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_cisco_aironet_series_2800_3800_access_point_deployment_guide/b_cisco_aironet_series_2800_3800_access_point_deployment_guide_chapter_01.html

Also look at powering options (as it require POE+ switch or power injector).

If you go without WLC, then there is an option called "Mobility Express" where given AP able to run as individually ( if you want few other AP can managed by that AP too)

http://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_Cisco_Mobility_Express_Deployment_Guide/b_cisco_aironet_series_2800_3800_access_point_deployment_guide_chapter_00.html

HTH

Rasika

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[dedrick]

Thank you for the information.

If I set the channel statically on a DFS channel, and radar pulse is detected, will it still hop to a new channel?

[Rasika Nayanajith · Accepted solution]

Hi

Pls refer below details, It appear that certain regulatory domain AP support DFS, not all regulatory domains. When DFS enable, AP will look for radar signals & automatically change its channel.

http://www.cisco.com/c/en/us/td/docs/wireless/access_point/atnms-ap-82/configuration/guide/cg-82-book/cg-chap6-radio.html

Dynamic Frequency Selection

Access points with 5-GHz radios configured at the factory for use in the United States, Europe, Singapore, Korea, Japan, Israel, and Taiwan now comply with regulations that require radio devices to use Dynamic Frequency Selection (DFS) to detect radar signals and avoid interfering with them. When an access points detects a radar on a certain channel, it avoids using that channel for 30 minutes. Radios configured for use in other regulatory domains do not use DFS.

When a DFS-enabled 5-GHz radio operates on one of the 15 channels listed in Table 6-3 , the access point automatically uses DFS to set the operating frequency. When DFS is enabled, the access point monitors its operating frequency for radar signals. If it detects radar signals on the channel, the access point takes these steps:

• Blocks new transmissions on the channel.
• Flushes the power-save client queues.
• Broadcasts an 802.11h channel-switch announcement.
• Disassociates remaining client devices.
• If participating in WDS, sends a DFS notification to the active WDS device that it is leaving the frequency.
• Randomly selects a different 5-GHz channel.
• If the channel selected is one of the channels in Table 6-3 , scans the new channel for radar signals for 60 seconds.
• If there are no radar signals on the new channel, enables beacons and accepts client associations.
• If participating in WDS, sends a DFS notification of its new operating frequency to the active WDS device.

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Note You cannot manually select a channel for DFS-enabled 5-GHz radios in some regions, depending on the regulatory requirements. The access points randomly selects a channel in that case.

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The full list of channels that require DFS is shown in Table 6-3 .

Table 6-3 DFS Channel List

Channel	Frequency	Channel	Frequency	Channel	Frequency
52	5260 MHz	104	5500 MHz	124	5620 MHz
56	5280 MHz	108	5520 MHz	128	5640 MHz
60	5300 MHz	112	5560 MHz	132	5660 MHz
64	5320 MHz	116	5580 MHz	136	5680 MHz
100	5500 MHz	120	5600 MHz	140	5700 MHz

For autonomous operation, DFS requires random channel selection among the channels listed in Table 6-3 . The channels not listed in Table 6-3 do not require random selection and may be manually configured.

Channels requiring Dynamic Frequency Selection (DFS) may be manually selected from the 5 GHz radio configuration menu. To know the DFS channels, use the show controllers d1 command.

The GUI/CLI used to manually configure non-DFS channels can also be used to select DFS channels as well. The default channel selection is "DFS", which randomly selects a channel.

If radar is detected on a manually configured DFS channel, the channel will be changed automatically and will not return to the configured channel.

Prior to transmitting on any channels listed in Table 6-3 , the access point radio performs a Channel Availability Check (CAC). The CAC is a 60 second scan for the presence of radar signals on the channel. The following sample messages are displayed on the access point console showing the beginning and end of the CAC scan:

*Mar 6 07:37:30.423: %DOT11-6-DFS_SCAN_START: DFS: Scanning frequency 5500 MHz for 60 seconds

*Mar 6 07:37:30.385: %DOT11-6-DFS_SCAN_COMPLETE: DFS scan complete on frequency 5500 MHz

When operating on any of the DFS channels listed in Table 6-3 , having already performed the CAC, the access point constantly monitors the channel for radar. If radar is detected, the access point stops forwarding data packets within 200 ms and broadcasts five beacons that include an 802.11h channel switch announcement, indicating the channel number that the access point begins using. The following example message displays on the access point console when radar is detected:

*Mar 6 12:35:09.750: %DOT11-6-DFS_TRIGGERED: DFS: triggered on frequency 5500 MHz

When radar is detected on a channel, that channel may not be used for 30 minutes. The access point maintains a flag in non-volatile storage for each channel that it detects radar on in the last 30 minutes. After 30 minutes, the flag is cleared for the corresponding channel. If the access point is rebooted before a flag is cleared, the non-occupancy time is reset to 30 minutes when the channel initializes.

HTH

Rasika

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