Fixed Channel Operations in the 5GHz range

[Jim Blake]

I am putting together a (Cisco 5520 WLC/3702i AP based) wireless network in a new building.

The overall building consultant has asked me to do all physical and logical networking design and deployment for wireless, with the exception of the deployment of the APs, which had been allocated to a Wireless consultant company prior to my engagement. Because the building is large and topologically complex, the consultants have specified deployment mandating not only required AP locations, but also fixing the channel allocation and transmit power for APs in both 2.4 and 5GHz bands, which they have asked I implement through commands issued to the WLC.

Aside from the fact that fixing power and channel makes deployment of an expensive and powerful Wireless LAN Controller largely pointless, I believe to do so will conflict with ETSI EN 301 893 V1.8.1 (2015-03), in so much as the WLC will not be able to implement DFS if radar is detected at any time. This is made more difficult because the specification includes the fixed use of the weather radar channels 120/124/128, as well as all other DFS channels. The location will almost certainly expose the network to radar, both from overhead and surface sources.

I have yet to lab-test the ability of the 5520 to set APs to operate locked to what should be DFS channels; that work will be done in the next days, and may prove the whole exercise impossible, but I would welcome comments from any others who have experienced this kind of requirement, and whether or not it is actually possible/permissible to do what has been requested.

Jim

[Skinner]

Jim,

I am very interested in knowing whether or not you tested the ability of WLC AP's being statically mapped 5GHz channels to perform DFS and "override" the statically mapped settings from the WLC?

The reason I ask is I am under the impression from all I read that DFS is mandated at the AP Firmware level. That the mechanism cannot be remotely controlled or overridden. In other words, you can build a static map for an AP on say channel 124 but if that AP radio hears any Radar on the channel DFS will override the WLC settings "autonomously". In a sense this means DFS is still an autonomous AP function. 

I am thinking the FCC would never allow such a protection mechanism to be controlled remotely. It would have to be an autonomous AP function or what would happen if the WLC lost connectivity to the AP's at a particular location?

I am very interested in your testing results. Can you share results on your fixed channel testing?