Tips carrying out a wireless (including N) survey.

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Jun 5th, 2009
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Hello all, I'm about to start a survey next week and i'd like to ask you expertise on it.I am using 1252Ap and airmagnet express edition to survey both 2.4/5 ghz (a,b,g,n),3 x 2422dg-r and 3x5135dg-r antennas.

First,I am in a doubt on how shall i place the ap during the survey. The customer, most probably, would like to install the ap inside the false ceiling.By reading the manuals of 1252 ap, i could understand that the ap (antennas) should face to the floor . So,during the survey shall i simulate this position ? What if, i place the ap in a vertical surface (wall) and carry out the survey? Will the results of this action reflect to the real ap mounting place( inside the false ceiling) ?

Second, the ap will have to accommodate both data and voice.I'm thinking to perform the survey two times for each floor,one for 2.4ghz and one for 5ghz. Which is the best practice to follow during the survey?

I would appreciate your opinion on these questions !

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jeff.kish Fri, 06/05/2009 - 07:00
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The unfortunate truth about a wireless survey is that you should do your absolute best to emulate working conditions during the survey. In other words, mount the APs as you will eventually mount them, and (if possible) conduct the survey during normal working hours/conditions.


So yes, mounting the AP on a vertical wall or mounting it differently than where it will eventually go will affect the survey results. It might not affect it that much, but it might also affect it enough to create dead spots.


As for the survey itself, you can conduct both 2.4GHz and 5GHz surveys at once. I'm familiar with AirMagnet, but not the express version, so this assumes it can handle both at once like the full version.


Another alternative is to simply perform a 5GHz survey. 2.4GHz RF energy propagates far better than 5GHz, and it's almost always a safe assumption that a 5GHz survey will work for a 2.4GHz deployment. This is only an option if you aren't required to produce both 5GHz and 2.4GHz maps, or something like that.


Finally, for voice surveys, be sure to use -67dBm as your threshold for RSSI. You also want to plan on 15-20% overlap of APs.


There are some thoughts. Have fun surveying!


Jeff

panayiotiscy Sun, 06/07/2009 - 06:10
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Hey jeff,thanks for your responce.Though, I have got some questions derived from your comments!

1) So let's say that i'm going to emulate the ap installation position (inside the false ceiling), how is this possible? To be more specific, all i mean how feasible is it to have somebody holding the ap above his head for a period of time while i am conducting the survey? Does this have to do with safety as well?

2)I'm going to follow your suggestion about conducting just one survey in order to save time!

Overall, i'd like to thank you for your message and comments!

Leo Laohoo Fri, 06/05/2009 - 17:38
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Hi Panayiotis,


I would to add to Jeff's comment:


The customer, most probably, would like to install the ap inside the false ceiling.

Can the false ceiling support the overall weight of the 1250 (power injector included maybe?)?


Have you tried using the 1140? I had the opportunity to test the 1140 and I found this model to be a viable financial alternative to the 1250.


The 1140, aesthetically speaking, is better suited to an office environment due to it's shape, thickness and color. You can hang this out, and like it's other brother the 1130, doesn't become too obvious behind the white ceiling tiles.

panayiotiscy Sun, 06/07/2009 - 06:13
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I just hope that it will support the weight of the 1250 because that's the ap we are installing there!

Is it possible to verify that the antennas of the 1250 ap have to face to the floor/ground in order to have the optimal results??? Thank you

dennischolmes Mon, 06/08/2009 - 07:19
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Yes for optimal performance face them down. Have you looked at an above ceiling antenna system like those created by Terrawave. They are much more effective than the rubber ducks provided by Cisco. Also the Cisco flat antenna works well.

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