What AP spacing do you use in your warehouse deployment?

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Just looking to see what people are finding on average their AP spacing is for connectivity in a warehouse environment once they have some some survey work. I am sitting at 170 to 200 feet apart. We have metal products in the shelves.

Andy
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Andy Cannarella

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Posted 5 years ago

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Crowdie, Champ

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How high is the access point being mounted and which antenna are you using with your AP-170? These factors will influence how far apart you place your access points.

I have worked at a number of warehouses with ceilings 12 to 13m up so, unless you are only using wireless scanners and don't mind some co-channel interference, semi-directional antenna aimed straight down to the warehouse floor are an excellent option.
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Andy Cannarella

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I use AP-340s with the statdard antenna kit in most my warehouses mounted 35 ft up. Getting ready to do my next one with AP-350s.

I am just polling what others are finding out works well for them. Maybe get some discussion going.

We use forklift mounted Intermec CV60 units running XP and a home grown picking system.
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Crowdie, Champ

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35 feet is approximately 10.6 meters so around the same height as my warehouse deployments.

If you deploy omni-directional antenna on your AP-340/350 access points then for every foot (meter) the signal goes down it will go sidewards considerably more - for this example we will work on a 7 to 1 ratio. So for your signal to drop down 35 feet (10.6 meters) it will go (using our assumed ratio) 245 feet (74.6 meters) across. Not all of that signal is usable as the clients are going to be below a large portion of it. The higher the gain on the omni-directional antenna the less the signal will propagate down to the warehouse floor.

The image to the left shows an omni-directional antenna at height while the image to the right shows the semi-directional at height aimed down at the ground. You can see that the use of a higher gain omni-directional antenna may result in little to no signal propagating to the warehouse floor.



With such a large percentage of the signal being directed parallel to the warehose room the 2.4 GHz radios in the access points will tone their transmit power back as they detect their neighbour access points with a very strong RSSI and this can also adversely affect the client experience down on the ground.

With omni-directional antennas in large open plan areas it is almost impossible to avoid 2.4 GHz co-channel interference and I have been called in to a couple of warehouses where the 2.4 GHz co-channel interference covered the entire warehouse. With legacy wireless scanners you will get away with this but it will cause issues when:

* Other wireless services are required in the warehouse
* An area, such as an administration area, immediately adjacent to the warehouse deploy wireless and want services such as VoWiFi.

If you have long picking ailses in the warehouse then semi-directional antennas mounting on the wall at the end of each aisle gives excellent results. Alternate the side of the aisle that the semi-directional antennas are mounted to avoid interference. So on aisle #1 have the semi-directional antenna mounted at the northern end of the aisle and on aisle #2 have the semi-directional antenna mounted at the southern end of the aisle.

If you have a warehouse that is away from the other buildings and only wireless scanners are deployed then you can almost deploy anything as the wireless scanners don't require high throughout or RSSI.

With my warehouse deployments I nearly always use semi-directional antenna so I can control the signal propagation and I try, where possible, to match the access point's transmit power to the radio specifications of the wireless clients, commonly wireless scanners.
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Robert Leavens

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CCI is acceptable in most warehouse environments, as there are few users, low bandwidth (low duty cycle).  Floor stock should need an AP every 40k sq feet, racked space, high density, AP every 15k sq feet.  Never let the controller adjust the power.  Set it at 50mW, lock it down.  If an engineer tells you an AP is needed every 2500 sq feet chase them away.  Always verify your work, you want 20% overlap of the cells for roaming (yes, this causes CCI, but you should be OK).  Duty cycle less than 75%.
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Andy Cannarella

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I tell you what, I have had no problem with the stock 4dBi antennas that I order with the APs in my warehouses. Even directly underneath the signal is not bad. I found that article where you got the pictures and comparing it to the Aerohive spec sheet the Aerohvie antennas definitely have more of a toroid shape instead of that flat line that is shown. Also have proven to work though testing and day to day use.

As I said I was looking to see what other users of Aerohive have for spacing in their warehouses. Just want to share real life experiences, tip and tricks.

Anyone else out there using Areohive in their warehouses?
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Crowdie, Champ

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I use that document to teach new wireless engineers about antenna and the effects of gain. I think you will agree that it is a pretty well written document. I believe the omni-directional antenna shown was 8 dBi. Hopefully the discussion will help anybody doing their first warehouse deployment.

The proof is in the pudding when it comes to your deployments. If they work and the customer is happy with then all is good.

For me personally I believe that the lack of Aerohive certified external antenna for their access points limits their use in some environments. If you compare the number of Aerohive certified external antenna to some of the other major wireless vendors you can see the issue.