08-21-2013 07:02 AM - edited 08-21-2013 07:04 AM
I'm designing a WLAN installation from scratch, no existing 802.11 deployment. The environment is a warehouse with challenging elements to RF: all the walls are metal, there are freezers, refrigeration rooms, frozen and fresh goods (seafood).
One room is a tall freezer with high shelving with frozen goods. The shelves move and the workers have to move them and work in between with their hand scanners. I'm thinking putting sector antennas on the wall and pointing them down the aisles. The aisles aren't very long, only a few meters actually, so I'm thinking a couple of AP's should be enough even it the shelves move a bit. Each AP could cover about two aisles depending on their position. Another option is to mount the AP's on top of the shelves and run the cables through the ceiling with enough slack to allow the shelves to move.
Any tips and possible caveats would be greatly appreciated!
The all-metal walls and cold environment makes me think I might need an AP in every room, even though some of the adjacent rooms are quite small. How much signal penetration and interference or multipath issues I should expect with metal walls? The scanners are going to be b/g only.
I'm going to use AP-175's as almost all of the environment is going to be either very cold or humid. Depending on the room I'm thinking about using down-tilt omni and low-gain sector antennas.
I'm reading Retail Wireless VRD and Chuck's presentation on the subject, great stuff and very helpful.
Thanks for all the tips!
08-21-2013 10:06 AM
Your mileage may vary (of course)
In our warehouse we've found that the end-of-aisle sector antennas work well, but it's one per aisle - trying to cover two hasn't worked very well. We have one exception where the sector antenna to the near end of the aisle is over 10 meters, any closer and the end-cap casts a shadow.
We're using ceiling mounted 105's in heated NEMA enclosures or 104's in the same enclosures and 4-6dB gain omni antennas outside the enclosures.
If I had it to design over again, I'd prefer to mount a bank of 104's on the outside of the freezer and use the lowest-loss cable I can get to deliver signal to ceiling mounted omnis. We've had trouble with CAT5 cable shattering at -10F
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08-22-2013 04:27 AM
Thanks for the tips! I'm also considering putting only antennas in some rooms and having AP's in another room or inside walls/ceiling. The moving shelving is a few meters from the wall where I'm thinking of putting the antennas but I guess only testing will tell how much issues the shelves are going to cause.
08-22-2013 06:11 AM
Depending on cost factors, sometimes drilling through freezer walls or ceilings can be more expensive than just buying outdoor NEMA-rated APs to deploy inside the freezer with a single borehole for the cabling. While cable brittleness is an issue, that's a pretty easy problem to solve. The AP-175s (good to -30C) with downtilt omnis on the ceilings or wall mounted with sectors may be a more overall cost effective solution than drilling through the freezers for LMR for every AP location.
Just another thought or option.
Sr. Techical Marketing Engineer
08-22-2013 06:30 AM
Agreed. It all hinges on how much of an issue boring multiple holes into a large freezer is for the HVAC and cooling guys. In some of my customer's spaces, the costs 'per-bore' amounts to about $1500-2500 (depending on the size, depth, part of the freezer, etc). At that point, the cost of a bore-hole and indoor AP equals an outdoor AP, and installation times are massively shorter when you can surface mount.
Sr. Techical Marketing Engineer