"Old school" wireless planning/ap placing

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Jul 9th, 2009
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Hello out there!

I have a question that needs to be answered by the "old school" engineers!

Here it goes: I need a plan ap placement for a very large indoor area.The area includes :open spaces,dry walls,walls etc.

I have tried some of the planning tools of the market,but are time consuming.Hence, i have decided to move on placing the ap using circles.

So, let's say that i am going to use 1141ap, is there some kind of method to estimate/calculate the radius of the circles ??

Well, this is it.I'm awaiting for your replies! Thank you!

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ericgarnel Thu, 07/09/2009 - 06:45
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It is best to use the equipment that you plan on deploying. You also have to consider the nature of the environment and the purpose/use of the wireless and plan accordingly.


calculating the cell size takes in account the bitrates/bands you plan on offering.

It is not as easy as picking a number


Given my environment, I am constantly surveying the wireless!

panayiotiscy Thu, 07/09/2009 - 09:04
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Ok, ericgarnel that's good. Can you consider that we would like to offer the coverage at the edge points at -85 dbs and 18mb/s data rate using 1141Ap. Combined with the n technology ,how long will the radius of this will be?

ericgarnel Thu, 07/09/2009 - 10:42
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If I dust off the old brain cells...

I think that the radius for 18mb bitrate is @150' for 5GHz & @120' for 2.4GHz based on a typical low gain omni. Granted, 802.11n will have a positive effect on non 802.11n clients too.

These are approximates and are not set in stone per variances in your environment.



panayiotiscy Sun, 07/12/2009 - 22:18
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At the bottom of this,we decided to move with 65m radius...Hope it will work out at the end.

markgreenwood Mon, 07/13/2009 - 05:27
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You have this backwards, the 5.8 cell is always smaller than the 2.4 cell. Sinces its half the wavelength.

ericgarnel Mon, 07/13/2009 - 07:26
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You are right, I transposed the numbers in my reply


Thanks

markgreenwood Mon, 07/13/2009 - 05:26
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I do a couple of things. from experience I try to space ap's about 100 to 150 feet apart in a honecomb configuration. That way I can achieve some level of channel separation. 2.4 GHz is channenging with only 3 channels, but 5.8 can give you anywhere from 11 to 24 (uni 2 extended).


Next thing, there are a couple tools you can use for this. Motorola has a program called Lan Planner or Etnerprise Planner..both do the same as far as designing and running simultations, but Enterprise planner includes the ability to model cellular and you can perform several types of prediction models and see them in 3d as well. They also have a tool for doing mesh and a couple others and a very powerful tool and is not a cheap tool. The other tool you can use is from Airmagnet..they have a wireless planning tool that is similar to enterprise planner exscept you dont get anything other than a heat map simulation. It will do the job if all you are looking for in an inexpensive too. I would also recommend at a minimum the Airmagnet Spectrum Analyzer as well..this will let you see whats in the air because you are bound to run into rogue devices, cordless phones and microwave ovens which will mess with any 2.4 GHz network. As well as seeing whats in the 5.8 spectrum.

scottmac Mon, 07/13/2009 - 07:41
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Cisco has a document/layout on their main site for using four freqs (without using non-USA frequencies.


If I can dig it up, I'll post a link.


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