40MHz and 80 MHz channel configuration

[Peter Boerjesson]

A thought struck me which I'm a bit uncertain of when it comes to the 40 and 80 MHz channels. I know how it works from a technological point of view and how to configure it in the WLC. However if choose to configuer a 40 MHz channel, which channels should I allow to make sure I will not get any overlapping channels? By default I've done this type of configuration with enable channels 36, 44, 52, and 60. My reason of thinking this way has simply been, make sure there's 40MHz available until the next channel pops up that a WLC can use. The WLC accept this configuration but recently I became uncertain if this works. Would the WLC perhaps interpret this as it's not allowed to use channels 40, 48 and so on so I would end up with only 20MHz channels anyway?

Have anyone seen any documentation or recommendations for configuring/channel planning regarding 40, 80 or 160 MHz wide channels?

If it make any difference I need to follow ETSI regulatory domain.

Br

//Peter

[mohanak]

Refer the links :

http://www.cisco.com/c/en/us/td/docs/wireless/technology/5760_deploy/CT5760_Controller_Deployment_Guide/802_11ac_support_on_WLC5760_and_Catalyst_3850.html

http://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-1/HDX-DG/b_hdx_dg_final/high_density_experience_features_in_release_8_1.html

[Peter Boerjesson]

These documents doesn't really answer my question. Lets look at the 2,4GHz band. If I allow channels 1-11 the access-points close to each other could end up on channel 1 and 3. As we know these overlap and would cause a lot of interference with each other. If you allow channels 1, 6 and 11 they wouldn't interfere with each other.

So lets assume I have two access-points and I'm running channels 36, 40, 44, 48 and I want to use 40 MHz channels, could access-point 1 then go on channel 36 (so using channel 36 and 40) and an access-point next be using channel 40 (so using channel 40 and 44 since it's 40MHz channel).

My think of not using channels 40 and 48 as my first post mentions was to avoid this scenario from popping up so I would have "none-overlapping" channels on the 5GHZ spectrum. I have found anything on how this is handled by the WLC and which channels you should choose (yes I realize that in the links provided they use all the channels, but they don't mention anything about the possibility of overlapping channels on 5GHz there.

[Peter Boerjesson]

To answer my own question after some testing and looking at DFS problem on one of the links I see that all channels need to be enabled or they won't be at 40/80 MHz channel size. As for potential overlap I am hoping cisco has solved that problem.

[Rasika Nayanajith]

I have two access-points and I'm running channels 36, 40, 44, 48 and I want to use 40 MHz channels, could access-point 1 then go on channel 36 (so using channel 36 and 40) and an access-point next be using channel 40 (so using channel 40 and 44 since it's 40MHz channel).

In this scenario, you need to enable all CH for DFS. if WLC choose CH36 and CH40 for the first AP then it will not use CH40 for 2nd AP. CH44 and CH48 will be used by 2nd AP.

When adding frequencies for DFS thinks in terms of 20MHz channels, do not get confused with channel width (20/40/80/etc)you planning to use.

HTH

Rasika

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