Impact of changing channel width and MBR?

[echoknight]

We are preparing to change the channel width from 40 mhz to 20 on our Cisco WLC.  Once this change is made, what kind of impact can we expect for the client devices? 

Also, we are adjusting the Data rates, removing mandatory for some of the lower rates and supporting others. What kind of impact can we expect for the client devices?

[Leo Laohoo]

If this change happens in global, the radios will need to be manually turned off before the settings could be changed. 

If this change happens on the RF Profile, the channels will change is highly dependent on the global setting of the Channel Assignment Method.

[Rasika Nayanajith]

40MHz to 20MHz should help to reduce CCI (Co Channel Interference) and should improve client performance if you alreday having higher CCI. Without knowing details of your existing RF environment it is difficult to comment about it.

Disable lower data rates & make 12Mbps mandatory/Basic should help to reduce airtime used for management frames like Beacon. This is a general best practice and you should get airtime efficiency.

HTH
Rasika
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[echoknight]

Thank you, yes this is why we are making the changes to offer the benefits you mention.  But my question was what kind of user impact can we expect directly after we we make the changes so we can plan our outage window accordingly.  

[ammahend · Accepted solution]

It can take up to 30 minutes (depending on how often DCA is configured to run) for the change to take effect.

when channel on AP changes all clients will disconnect, I would plan the changes after hours.