Re: Non-overlapping channel (1/6/11) isn't always optimal

[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

In <91jo225f2f7i48fpv0mkkctfor8m9e8dle@xxxxxxx> on Thu, 30 Mar 2006 14:32:48
-0700, Aaron Leonard <Aaron@xxxxxxxxx> wrote:

~ My point is that 1, 6, and 11 aren't necessarily optimal.
~
~ In fact 1, 6, and 11 are only really optimal in terms of minimizing
~ interference when you control multiple overlapping access points, and even
~ then they aren't necessarily optimal -- 4 channel spacing (e.g., 1, 4, 8, and
~ 11) will allow 4 access points (instead of just 3) to overlap with minimal
~ interference.

Our test results do not concur (assuming that you control your RF
environment). The interference created by using 1/4/8/11 rather
than 1/6/11 channel spacing will give you less aggregate throughput
throughput the 2.4GHz band. With 4 APs, you are better off having two on
the same channel.

That's not my experience, which is consistent with these documents:

4 Simultaneous Channels Okay For 802.11b
<http://www.extremetech.com/article2/0,3973,708876,00.asp>

The Overlapping Channel Problem
<http://www.ja.net/services/publications/factsheets/063-overlapping-channel-problem-v2.pdf>

WiFi was *designed* to support many interfering, overlapping networks,
handling the resultant packet collisions with minimum fuss.

Channel Overlap Calculations for 802.11b Networks
<http://www.cirond.com/whitepapers/FourPoint.pdf>

This is because, with multiple BSSIDs on a single channel, the 802.11 MAC
can (potentially) recognize the signals from the other BSSID as being valid
802.11 frames, and can hence do an informed backoff/transmission. With
multiple BSSIDs on adjacent overlapping channels, the other BSSID's
transmissions are just perceived as noise.

http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00802846a2.html

As it notes, that paper is at odds with the other authorities. In addition,
the only supporting test was both limited and highly artificial.

It may be that what works best is different in different types of
environments.

--
Best regards, SEE THE FAQ FOR ALT.INTERNET.WIRELESS AT
John Navas <http://en.wikibooks.org/wiki/FAQ_for_alt.internet.wireless>
.

Quantcast