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b/g/n and a/n configuration


I am using WLC 4404 and wireless is configured....

I dont have much knowledge of RF.. so anyone can help me with this?

There are two options in wireless tab, 802.11a/n and 802.11b/g/n.

In 802.11a/n--> DCA, channels are configured as 36, 40, 44, 48, 52, 56, 60, 64, 149, 153, 157, 161

in 802.11b/g/n--> DCA, channels are configured as 1,6,11

My questions are,

1. What exactly DCA is?

2. WHy the channels are different for both bands(802.11a/n and b/g/n) ?

Your help would be appriciated.

New Member

Re: b/g/n and a/n configuration

please find the attached images from WLC.

if you want to know anything further, please let me know.

Re: b/g/n and a/n configuration

adding some more info on top of what Leo has metnioned:

DCA is an algorithm used to pick up the most appropriate channel for the AP. to decide most appropriate channel the WLC checks the neighbor RF channels for an AP and picks up the most appropriate one with the least noise and/or interference.

For DCA to work among different controllers you need to configure same RF group name under the controller config (from controller tab). APs should hear each other at least @ -80 dBm or; if RSSI is less than -80 dbM (-85 dBm for example) DCA is not going to work.

Here are some useful links describing all what you need to know about DCA, TPC and coverage hole detection (all of those are under Radio Resource Management [RRM]). you will enjoy them if you have sometime to read

about your second qeustion:

In wireless there are two bands operating 802.11a (this works on 5 GHz band) and 802.11b/g (This works in 2.4 GHz band).

802.11a have more channels to use than 802.11b/g.

802.11b/g has only 14 channels (in most countries only 13 of those are usable. AFAIK only Japan allows channel number 14).

802.11a has about 20+ channels.

This wikipedia link could be useful for you:



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b/g/n and a/n configuration

DCA stands for Dynamic Channel Assignment.  It's self-explanatory.

Let's go back to autonomous IOS/WAPs.  Without using the WLC, the operator configures the channel each radio of each WAPs will operate on.  With the WLC (and if DCA is enabled), the WLC will coordinate among the WAPs and change channels accordingly so you won't get channel interferrence.

Now there's another feature that you didn't ask and it's called the TPC or Transmit Power Control.  Like the DCA, if it's enabled, the WLC will adjust the transmission of each radio of each WAP accordingly. 

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