Wireless Access

Owing to building design and aesthetic concerns, it seems certain I will need to locate APs (220 series) above the ceiling tiles, in a large office space - most likely without the ability to use off-board antennas beow the tiles.   If we put 225s in the void above, quite apart from the obvious dB loss introduced by the ceiling tiles themselves (which we can at least test), I have concerns that a fairly dense mesh of APs will 'see' each other, above those tiles, in quite a different way - with lower signal loss - than the way APs will see connected clients.   How, in particular, is this likely to affect ARM operations specifically and the subsequent performance of the WLAN?

You are correct, depending on the height above the ceiling tiles, the crowdedness of the plenum (HVAC, ladder racks, etc), etc will impact how ARM and the APs work. In some cases the openess of the plenum will create issues where the APs 'see' themselves and pick different powers and channels than would be selected if the APs were in the user space. Additionally, if an AP is within a 'dense' area of the plenum, it may affect the coverage below the AP if the HVAC and ductwork obstructs the RF propagaion.

The 'fix' (as it were) is to adjust the min and max arm values accordingly when needed, possibly statically set.

A better thing to do, when concerned with aesthetics and you don't have an open plenum for the RF propagation to the floor, is to look at the 224 and use either our ANT-16 or something like the Terrawave antennas (all listed below), leave the AP in the plenu and put a non-descript plastic package radome within the user space. These antennas look like all the other stuff you would have (fire alarms, sensors, etc). It also is good for locating APs when trying to troubleshoot since often AP locations are not marked and you end up with a plashlight and a ladder spending all day looking for an AP.

The Terrawave and Aruba 3x3 MIMO antennsa all work great, and keep your APs working optimally without having to worry about plenum issues.

http://www.arubanetworks.com/pdf/products/ap-ant-16_ss.pdf

http://www.terra-wave.com/shop/245-ghz-34-dbi-3-pack-mini-mimo-omnidirectional-antenna-with-plenum-pigtails-and-rpsma-plug-connector-p-1529.html

http://www.terra-wave.com/shop/80211nac-245-ghz-355-dbi-3-pack-mini-omnidirectional-antenna-with-plenum-pigtails-and-rpsma-plug-connector-p-2969.html

Hi Jerrod - many thanks for your reply.  I had already suggested ANT-16s and 'below-the-tile' solutions are definitely my preferred approach (I've had success with Terrawave antennas in the past too, so will look further at those).  Everything is apparently down to what architects / clients will accept!   Your point about knowing the location of APs by their ceiling-mount antennas is a good one, which I hadn't thought of before...