40Mhz channel bonding direction on Cisco 980

[rnrnerdski]

Is there a way to control 40Mhz channel bonding direction on Cisco 9800 controllers to prevent OBSS? Sometimes I see ch36 as primary and sometimes ch40. 

[Leo Laohoo]

In GUI, Configure > Tag & Profiles > RF/Radio.

Pick an RF Profile Name in question and then go to RRM > DCA.

[rnrnerdski]

Maybe I didn't frame my question correctly. It's not about how to enable 40MHz channels.

Once 40MHz wide channels are in use: can the bonding DIRECTION (up/down) be specified?

For example:
Is there a way to make sure ch36 is always the primary when bonding 36 and 40 to avoid ACI? Same for other pairs?

[Leo Laohoo · Accepted solution]

Yes and no. 

No, RRM and DCA will decide which channels (and Tx power) to assign each AP based on the "noise" each AP can hear.  

Yes, it can be done.  For those who would like to "micro-manage" the behaviour of each AP, 9800 is the answer.  For example, each AP can be assigned/micro-managed to by creating an RF Profile and assigned a range of channels to use.  

[rnrnerdski]

Thanks. That's what  I thought. Definitely don't want to "micro-manage" APs, but specifying a bonding direction would be nice to avoid ACI. I've seen too many APs next to each other with 36P and 40P. Some other vendors do let you pick if you want to bond up or down. 

[JPavonM]

ACI concept does not exactly apply on 5 GHz band as channels do not overlap (at least not between the end of the 'shoulders' at -28 dBm, which the usable portion of the wave).

Letting the APs to be configured in that way increase capacity by reducing contention in case there would be no option to transmit using channel bonding but only the 20MHz channels.

[rnrnerdski]

Understood. I guess the correct term would be OBSS, not ACI. 

[eglinsky2012]

To be crystal clear, and provide photographic evidence of this behavior, I think this is what the OP is looking to avoid.

Why are some APs assigned channel 44 primary and channel 48 as extension but some are 48 primary and 44 extension? What are the pros/cons to this as opposed to all APs using these bonded channels using 44 primary and 48 extension?

These are two 2800s, both on 40 MHz using RRM, installed in the same building. I did an RRM restart this morning due to AP replacements in different buildings, so this is the best RRM can come up with.

[rnrnerdski]

This is exactly it. Thanks for the supporting evidence!