Small question, big answer.
The first things to consider are the materials in the environment and their tendency to reflect or absorb signals. Next would be interference from existing devices, which probably cannot be removed.
I would start with two things:
1. Spectrum Analysis - you can hire someone to come out with $1000s in equipment to tell you how much signal/interference you have at different frequencies, OR you can buy a Proxim RangeLAN2 card and run the Snoop program in their Site Survey. Slow mode will monitor each 1MHz portion of the 2.4-2.484GHz band for 1 second each.
Get a MMCX to N jumper and a high gain path or yagi and walk around the plant to see if you have signal or interference at 1.4GHz.
2. Demo/Pilot - get a 350 AP plus 350PCM and 350 LMC cards and see how far you can go at 1, 2, 5.5 and 11Mbps in the deepest darkest part of the plant. Use the Patch and/or Yagi (from #1 above) on the AP and try placing it up high, pointing down.
Or, send us blueprints and we'll give you a +/- 20% accurate spec from those.
Matt
