Channel width in .11n

[rahul nair]

Hi ,
I have a situation.
According to what I have read .11n uses a channel width of 40mhz for better bandwidth .
Yesterday while troubleshooting for some speed issues at my company , I stumbled upon a setting in 802.11b/g/n radio settings , in the configuration page .

Where it mentioned that , the channel width under use is 20mhz.
How come that is possible ?
Should not it be changed to 40 MHz ?


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[Leo Laohoo]

How come that is possible ?

It is technically NOT possible to channel width 802.11b/g because of the LIMITED amount of channels to play with.

[rahul nair]

Err.. b/g ?
Actually I am talking about .11n .

And it does allow me to change to 40mhz by selecting the custom option but I am not sure whether to do it , also I wonder why it has been defaulted to 20 MHz in an AP with .11n radio.

Sorry if I am missing something here.

Please correct me if I am wrong .


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[Leo Laohoo]

802.11n occurs when you channel bond 802.11 a to 40 Mhz.

You will NEVER be able to channel bond 802.11 b/g.

[Amjad Abdullah]

I remember earlier with cisco WLC code it was possible to bond 2.4 GHz channel in 40 MHz. With later releases they removed this and it is no longer possible.

I don't exactly remember what version was supporting that, maybe 6.0.196.0 or 6.0.199.x. I don't exactly remember. But what I remember that it was there and later the feature was removed.

Why removed? Just like what Leo explained, there are only 3 non-overlapping channels in 2.4 GHz ISM band. If you bond two channels in 40 MHz then there will be no more non-overlapping channels available for channel-reuse pattern. So, because that is not feasible it was removed.

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[marstoyanoff · Accepted solution]

Hi Rahul,

Please follow the steps in the following link:

http://www.cisco.com/en/US/products/ps6366/products_tech_note09186a0080a3443f.shtml

I hope this helps.

Marty

[rahul nair]

Ohh..I get it now guys !
Thank you .




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[Scott Fella]

It was possible with early release when the 1252 APs came out to channel bond 2.4ghz. You no longer have that option with any if the Cisco enterprise equipment. The small office home office devices still allow you to channel bond in the 2.4ghz but not any of the enterprise Cisco wireless devices.

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