WAP's under Raised Floor

I'm in the process of doing the telecom design for a high-tech building that has raised floors throughout. The question came up of putting the WAP's under the raised floor, as that is where all the Cat6 cabling is.

The building will have cubicles and configurable floor to ceiling office walls/doors. Having some experience with Wi-Fi, I originally designed the WAP's and antennas to be mounted in the ceiling, as that is the way to get the best coverage.

My question is, if the WAP's were to be installed under the raised floor, where would you mount the antennas and what kind of antennas would be used?

whats the building size/ number of floors etc, incidentaly why do you need wirless if you can hide the cables so easily?

you could also easily install 'leaky cable'

__________________
to infinity and beyond (assuming a perfect vacum of course)

The building is about 200,000 sq ft, concrete/steel construction, with three wings in a "tapered" design with one wing being six levels, the middle one being five and the last wing being three levels. The raised floor tiles are alluminum and well grounded. They want wireless for their laptops (roaming capability) and for RFID asset tagging.

i have been mulling this over before a posted a reply.

to sum it up, it would be best as you said if the wirless routers were above the grounded floor, or at least if the antennas could be.

i was wondering on how usefull a leaky cable would be. for them to work properly they need a miniumum of 4 inches of clear space and prefarably six inches of space free from any metal or similiar material (this would probably include concrete too). so that a clear signal can pass through the cable. If you can acheive this then it might be able to propergate a signal above the grounded aluminium floor, but would more likely provide a signal to the floor below.

so to get to the point, if you want an attractive anntena for an office enviroment, just do a google search for 'wireless router celing / wall antenna', there are plenty of atractive wall and ceiling mounted units avaliable, if looks are not important then go with whatever anntena you can find and offer the best performance / price, just make sure that

1, you run the shortest length of pig tail from the antenna to the router as possible and that it is of the highest quality you can afford to reduce signal loss.

2, you match the right connection type from the router to the pigtail.

3, in your case i would say stick with omni directional antennas. directional anntenas as you probably know send the signal in a specific direction. With a building this size just mount an omni 10 or 20 meters in from the outside walls and stagger additional anntenas from repeater stations or other wirless access points wired into the network

4 if you use repeater stations to propergate your signal then it will be possible to keep all of your stations on the same channel, If you use a wired bridge approach (numerous access points wired into the network), then you would probaly have to have each adjacent station on a seperate channel to avoid interference.

5 try to keep as many connections as possible as a hard wired connection, the fewer wirless conections the better, this reduces radio interference within the building.

well, i hope this helps let me know how it goes
simon

edit - im also interested in what others think of this particuarly geocorona as he / she seems particuarly knowlegable about this!

__________________
to infinity and beyond (assuming a perfect vacum of course)

Well, most omnidirectional antennas tend to have an area of coverage that's flatly shaped like a discus; so if they're used, they shouldn't be in the floors/ceilings, but rather the walls (oriented vertically).

This omnidirectional ( 2.3 GHz to 6 GHz Broadband/Multi-Band 3 dBi Wireless LAN Compact Ceiling Mount Omni-Directional Wi-Fi® Antenna ) might work in a floor, and not only cover wifi G & B at 2.4 GHz, but also wifi A at 5.7-5.8 GHz.

Whether it's appropriate is a question for the manufacturer.

I don't know how badly the ceiling material would degrade the signal, but an antenna recessed between steel I-beams would have some of its effectiveness clipped by the beams.

I would not even consider the possibility that an enclosed antenna would serve the floor above it, with those aluminum tiles certainly destroying the upward signal.

If you're talking about the antennas being encased on all sides by either concrete, steel beams or aluminum tiles, then it's not a worthwhile pursuit, but there's no reason you can't hide the electronics there. The antennas would just have to be on/in the walls or on the ceilings. There are all sorts of solutions, and they don't have to be ugly. Wall-mounted patch or biquad antennas could be covered with non-metallic artwork.

Yes I've used those types of antennas before with the "donut" beam.

The problem I'm faced with is that the client wants to be able to change the cubicles and offices around from one month to the next. So putting a WAP in the floor with the antenna close by would seem in impossibility in this kind of environment. Even though it is a raised floor.

I was hoping there would be some kind of "floor" antenna, perhaps one to replace a typical 2x2 tile - that would be cool, but probably expensive. And coverage would probably be an issue.

I'll have to investigate "leaky cable" a little more as that is looking like a possibility. I wonder if it is expensive. Here's one that was at the top of Google.

At this point, I'm still inclinded to put them in the ceiling, more so you won't have to worry about them when the floor plans change (i.e. the ceiling tiles, beams, lights, etc. won't be changing).

Thanks for all your replies (siwillems and geocorona). I'll let you know what is decided. And if you think of anything else, please post! Thanks again!

I'm sure antennas could be custom built to replace floor tiles (they burn antennas into circuit boards), but I doubt the power or efficiency would match the cost.