Mounting 1131AG onto reinforced concrete

Unanswered Question
Jan 30th, 2007

Hi all

I got a small boggle about the do's and don?ts of mounting 1131AG access points.

It states clearly that you should not mount the AP's within 3ft of any metal object.

The install guide has illustrations of APs being mounted either under the ceiling tiles or suspended just above the ceiling tiles with special brackets.

I'm about to install 192 AP's into a high rise office complex. The Architects are hell bent on mounting the AP's , over the ceiling tiles, in the ceiling cavity directly onto the above reinforced concrete floor.

My site survey was done, mounting the AP's to the under side of the removable ceiling. And all worked fine that way.

Does any see a problem or has ever experience a problem, mounting the AP's mounting plate directly onto reinforced concrete?

Will the reinforced concrete inhibit or change the characteristics of the wireless signal even thou the AP is aiming away from the concrete?

Keeping in mind that the roof of each floor is also littered with metal Air Con ducts, high voltage wiring and fire sprinkler piping.

Thx guys

Dale

I have this problem too.
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scottmac Tue, 01/30/2007 - 20:37

You should re-do the site survey.

Aside from the various obstructions (many of which kill the "line of sight" to the client and / or cause additional multipath), there are steel re-rod & mesh in the concrete (more than likely) ... proximity of these to the radiating element of the AP will mutilate your RF patterns.

Remember that for 802.11g, the wavelength is ~5 inches. Every ~2.75" you move the AP will change the pattern of coverage.

If you aren't putting the APs in the location you used as the premise of your site survey (or vice-versa actually .... put the APs where the site survey says you need 'em) ... the site survey is basically invalid.

You might be able to change the APs to a different type with external antennas and make up some of the diffence that way (tailor the antenna pattern some), but again, they all radiate differently than the antennas you surveyed.

IMHO, you'd do well to scrap the original survey and do it again with the test units in the correct position. There's no other way to do it and still be able to guarantee proper coverage.

FWIW

Good Luck

Scott

koeppend Wed, 01/31/2007 - 18:21

Hi Scott

Thx for the info, did a single floor survey.

It was the worst set of results I have ever seen due to the amount of metal Air ducts, piping, and silver foil and steel cable trays. Line of Sight is everything.

Thanks for your advice, I was going to do the survey anyway, just need to see if anyone had experience mounting these things on reinforced concrete.

This just back up Cisco recommendation, to keep AP's at least 3ft away from metal object where possible. Its amazing how much the signal can be affected.

Regards

Dale

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