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Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

2 recommendations

FYI: 802.11b channel assignments

I've been doing a bit of research on 802.11b from an engineering point of view, and in the process got a pretty good handle on how 'channels' work. There is substantial overlap, so (for instance) channels 1 and 2 have almost complete overlap.

Thought this diagram might be illustrative.

Steve
--
Stephen J. Friedl * Security Consultant * Tustin, California USA * my web site


File Quit
Mac Geek
Premium
join:2002-11-28
San Antonio, TX

very interesting... i didnt think there was much difference between the channels.



Fraggboy
Just Lovin' My Bandwidth . .
Premium
join:2001-03-04
Las Vegas, NV
reply to Steve

So, with the above info, what would be the "Best" channel to use?! Sorry, I'm not that good when it comes to "Technical" stuff.
--
My Boss treats me like a Mushroom.. Keeps me in the dark, and feeds me Bull$hit!!



Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

If you have no other access points nearby, it doesn't matter at all. If you *do* have other access points nearby, pick a channel that overlaps least with the others in the area.

Steve
--
Stephen J. Friedl * Security Consultant * Tustin, California USA * my web site



Fraggboy
Just Lovin' My Bandwidth . .
Premium
join:2001-03-04
Las Vegas, NV

Ahh, Gotcha. Thx Steve. It seems like the "Best" channels to pick would be 5 or 10. They seem the least amount of overlapping other channels..
--
My Boss treats me like a Mushroom.. Keeps me in the dark, and feeds me Bull$hit!!


taxi9

join:2003-04-20
Ridgefield, WA

The "Best" channels to use are 1, 6, and 11. That way you have three non overlapping channels to pick from, not just two.


DSLrgm
Premium,MVM
join:2002-08-22
Oak Park, MI
reply to Steve

A while back, someone posted how to do 4 channels with careful layout.

I would like to find that message....



Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

said by DSLrgm:
I would like to find that message....
I exist only to serve

»www.extremetech.com/article2/0,3···8,00.asp
--
Stephen J. Friedl * Security Consultant * Tustin, California USA * my web site

tommnor

join:2003-01-03
San Jose, CA
reply to Steve

That is just about the best diagram I have seen that explains the 3 non-overlapping channels........



Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

said by tommnor:
That is just about the best diagram I have seen that explains the 3 non-overlapping channels........
... which is why I created it. I just couldn't visualize all the frequency tables without a lot of effort, and this breaks it down in something that can be understood in about 15 seconds. Took about an hour in PaintShop Pro.

Steve
--
Stephen J. Friedl * Security Consultant * Tustin, California USA * my web site


jefe
Premium
join:2001-05-19
Northport, NY

I must be missing something.

It looks like all the channels overlap to some degree.

Does not ch11 overlap ch 10 from about 2450 MHz through about 2469 or so?

If there's a channel in that chart that doesn't overlap another, I sure don't see it.



Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

channel 1 doesn't overlap channel 6, which doesn't overlap channel 11



jefe
Premium
join:2001-05-19
Northport, NY

But Channel 1 overlaps 2, 3, 4 and 5.

If you are only concerned with interference among your own devices I guess you could choose 1 and 11 and be in business. But you have no control over the myriad of devices other people in the neighborhood are using or what channels they're on. So just because you choose Channel 11 doesn't mean you won't be overlapping somebody else's radio.

Right, Steve?



Steve
I know your IP address
Consultant
join:2001-03-10
Yorba Linda, CA
kudos:5

Channel coordination does indeed require actual coordination, and in a dense area there may simply not be enough bandwidth to add one more access point without interference.

I'm lucky that none of my neighbors has wireless, but every now and then I power my WAP down and hook up the external antenna and do a scan: if I found a neighbor overlapped my channel, I'd move my channel to one that didn't.

If I had two neighbors that spanned channels such that there was no non-interfering channel, I'd have to either live with the reduced bandwidth, or talk to my neighbors about sharing efficiently.

Or, I suppose I could always hack their access point and change the channel myself

Steve
--
Stephen J. Friedl * Security Consultant * Tustin, California USA * my web site



jefe
Premium
join:2001-05-19
Northport, NY

I'm glad you're not my neighbor Steve.

Although I'm the ultimate good neighbor when it comes to not polluting the spectrum unnecessarily. I remove the AC power to my WAP when I'm not using it, which is most of the time.



Shiftlock

join:2002-03-22
Naples, FL
reply to Steve

Unless you live in a rural area, I'm not sure it really matters what channel you choose, since I suspect you will receive much more interference from 2.4 GHz cordless phones than you will from other 802.11b products.


cgo5

join:2002-08-14
reply to Steve

Steve.....i have done a bit of research myself. Besides the channel overlapping issue, another interesting point is about the power in each channel. While most people assumed that the power are the same, in fact after looking some technical detail paper from some vendors about their product, there seems to be different power on each channel. This info can be found at the fcc site. I have not have enough time to compile the information into a documentation. Maybe in the future.


taxi9

join:2003-04-20
Ridgefield, WA
reply to Shiftlock

I have my 2.4GHz cordless phone sitting with in 5ft. of my AP and I have yet to have it cause any issues. I have tried to make it cause issues, but they just seem to get along.

Here's a question, does the channels on a 2.4GHz cordless phone correspond to the channels of 802.11b as far as there frequency range?



ryanjo9

join:2001-09-17
Lake Mary, FL

Many 2.4 GHz cordless telephones operate with what is called frequency hopping technology. This technology utilizes the entire frequency range also used by 802.11b wireless devices. Thus changing the channel of the Access Point may not eliminate the interference problem.