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Wireless Standards

Posted on 2012-09-14
Medium Priority
Last Modified: 2012-09-16
We have a decent wireless setup at a school where 98% percent of the school has a signal. It is basically 9 Cisco Aironet LIghtwieghts with a Ciaco Controller.

Never really had any issues with it however a coworker attended a seminar and was given some info on wireless and to me it sounds like salesman trying to make a sale.

So I would like comments or suggestions and if possible a link showing it.

I am not a wireless expert. My job is network administrator/engineer meaning I just configure switches, router, firewalls, and servers.

What are the industry standards for wireless 802.11 a,b,g, and n in relation to workstation to access point ratio.

He was told for best connection and throughput the magic number is 20 laptops to an access point.

Also what are the recommended distances between APs.
Question by:pclinuxguru
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Darr247 earned 1000 total points
ID: 38399257
There is no 'standard' for user to AP ratio, though up to 40 is suitable; 10 to 20 is usual.
I believe the Cisco APs can theoretically handle up to 2048 connections, but they recommend limiting it to 24 for best performance.

Here's best practices for designing your WLAN...
who designed the current setup for you, and who installed it?
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Author Comment

ID: 38399493
I did... basically I dropped an access point and walked until I lost signal then dropped another one until I could walk from one end of the building to the other without losing signal.

This was about 4 years ago.
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Expert Comment

ID: 38399745
> walk from one end of the building to the other without losing signal

Not unreasonable, but other devices could give better or worse results than the one used to do that setup.

You can get a good graphical picture of wireless networks on your site using a tool sich as MetaGeek's open source inSSIDer, as well as comparing the received signal strength indication. Though RSSI is an arbitrary metric rather a defined unit of measure like PSI or newton-meter, it can still be used to compare the relative strength of signals from the same point of measurement.
The closer to 0 dB that reading is, the stronger the signal. e.g. an RSSI of -90 dB might be a steady connection on one machine and that same reading on a different laptop might not be enough signal to stay connected... but if one AP gives an RSSI of -70 dB from 100 feet away and the other APs give an RSSI of -60 dB from 100 feet away, on the same laptop, you should check into what might be blocking or attenuating the signal on the first AP.
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Assisted Solution

ChiefIT earned 1000 total points
ID: 38403001
""basically I dropped an access point and walked until I lost signal then dropped another one until I could walk from one end of the building to the other without losing signal.""

I am CRACKING UP.. !!! Finally, someone with their head screwed on straight.
It's funny how the easiest ideas are always the best. Truth is, the practices you already applied by dropping an AP when the area runs out is exactly what most RF professionals do. Some invest in Spectrum Analyzers to perform site surveys of signal levels and Signal to Noise ratios. Yet, some do exactly what you are doing. The Spec An has one added feature. You can see noise or other APs that will interfere with yours and channels that are cleaner than the war zone that most default to.

You can always look up the differences in frequencies and the differences between A, B, G, and N. You Might even get a ballpark figure of how far the effective range is at max power for that AP. Truth is, Radio Frequency Interference is such abstract math and physics that there is no way to tell someone how to place access points. You just have to get a feel for it, just like you did.

Just keep your APs away from cordless phone bases and Microwaves. Those two operate at or around the same frequency as your wireless. And consider changing channels to a non-volatile war zone.
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Author Comment

ID: 38403264
What about refrigerators?

Almost every classroom has a microwave a one of those tiny refrigerators... Cordless phone don't exist unless you mean cell phones.

I never thought of the appliances though.

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