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Acceptable signal to noise ratio...

Posted on 2009-07-15
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Hello everyone.  I'm sure this will be more of an opinion based answer, but here goes:  I work for a local school system and we are currently trying to make some of the high schools completely wireless.  We've taken our WAPs up to our different halls and tried different placement just to see what kind of numbers we get (using a program called NetStumbler v3.01 I believe if that matters).  I was mainly just wondering what others have decided to use as their "acceptable" signal to noise ratio - of course we all want it to be next to nothing, but we're on a budget!  Any thoughts would be appreciated.

Thanks.
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Question by:BryantBW
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by:selvol
ID: 24860189
32+ is considered by me to be the exceptable line . Anything less than that should be addressed if you're experiencing problems.
Try Placing the AP as High as possible.  Away from electric lines.. ETC.  As I am sure yo know.  
There are many Factors..
The easiest way for improvement would is Upgrading antennas. Or Placing A back plate of thin solid metal behind the AP that are intended to be directional. Or in placed that you wish to keep the signal away from. As the Metal will help block and signal and act as a reflector of the signal.  You only get a set amount of power per AP.. So if you have a non directional antenna like a rubber duck. You will have the power radiate in all directions.  Where if you focused the energy you would have that same energy going in the direction of the focus.  By focus I mean a directional antenna or dish. Or the metal plate I mentioned.  
Any thing that conducts electricity is an antenna. And can effect the signal in a bad or good way.  
So many variables . And I am a little rusty on the subject. I used to do extensive wifi related stuff.
 
http://www.nortekusa.com/principles/VelocimeterAccuracy.html
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by:BryantBW
ID: 24860741
Hmm... some interesting points there.  I'm more of a cable guy, so this wi-fi stuff, other than the configuration is kind of cloudy.  What we've considered doing is getting a 200mb file and transferring it from a server to the laptop over wireless in some of the worst areas to see how fast/slow it really is.  Every one of our users have roaming profiles, with the max quota being around 200mb (minus a few exceptions), so that's our main worry.  I'll look over the notes and see if the 32+ rule can apply.
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selvol earned 200 total points
ID: 24861232
Yea, its just a rule. It can be broken.  It just depends on the amount of funds available for a project. 32 might be high. But it is not a must.  Data quality is really only effected up to a 20 SNR.  Above that the effect is minimal. I just like to give it room for a cloudy day. Literally. Clouds effect signal. Water in the clods.  Also the 32 takes in to effect a slient with a sub-par card.  
I never caught what freq. yo were using? 2400mhz or 5800mhz ?  Other?
Regards.
 Selvol
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by:BryantBW
ID: 24865227
We're using 2.4ghz... nobody will spring for the enterprise grade WAPs we want to buy (we've even offered to throw in the controller out of our budget!).  Linksys WAP54G's are what we have at the moment - we hate them, but they're cheap and do the job.  One school has 17 of them, and anytime we want to update a setting, it's a royal pain.  Well thank you for the insight, that's basically what I was looking for, just what everybody used and we'll see if that can fit our stuff.  Thanks a lot!
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