802.11n and Ap density

Unanswered Question
Aug 27th, 2009

hi to all!

I'm trying to deploy many 1142 aps with 5500 controller. All aps will be near each other so it will be high ap density. To avoid interference issue i'm thinking

to activate RRM on controller and 40 mhz channel on 802.11n 5Ghz. With this configuration, among others, i reach 300 Mbps, but i have some questions:

According to this config, do i keep 3 non-overlapping channels on 802.11n 2,4 Ghz?

Do i keep the 12 non-overlapping channels on 802.11n 5ghz?

Thanks for your help.

I have this problem too.
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Robert.N.Barrett_2 Thu, 08/27/2009 - 05:40

You'll want to use 20 MHz channels in the 2.4GHz band. That's the only way to get the 3 non-overlapping channels (channels 1, 6, and 11). When you switch to 40 MHz channels, then you end up with one non-overlapping channel because you have to bond 1 & 6 or 6 & 11 to get the 40 MHz channel.

I don't have my 5 GHz channel list handy, but if you normally have 12 non-overlapping channels at 20 MHz widths, then you will have half that when you enable 40MHz channel widths.

uosambela Mon, 09/07/2009 - 04:07

Thanks for your answer, Robert.

I configured my WLC according to my previous post:RRM, 40 Mhz on 802.11n 5Ghz, 20Mhz on 802.11n 2,4 Ghz, etc.

Sometimes i get 300 mbps speed (when i connect to 802.11n 5Ghz), but when i'm connected to 802.11n 2,4 i just get 144.

Is there a way to keep always 300mbps speed?

thanks in advance

Robert.N.Barrett_2 Mon, 09/14/2009 - 08:29

I have not done a lot of testing with 802.11n on a controller (just played around at home with a few standalone APs). All things being equal, your difference in channels widths is (40Mhz on the 5Ghz versus 20MHz on the 2.4GHz) explains the speed difference.

Also, be aware that speeds will typically jump around depending on your location (with respect to the AP), how many other clients are associated to the AP, the presence of 802.11a/g clients, the presence of 802.11b clients, interference, and a whole host of other factors. Don't expect to always get the best speed from your APs - even if you are 3 feet from one.

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