Wireless Site Survey

Hi, I need to do a wireless site survey for a warehouse.
the deployment was already made by previous technician who is no longer with our company.  The warehouse has approx 125bAruba APs model AP-125s with controller PowerConnect W-6000 M3

there are staff in the warehouse who use PSION Teklogix Workabout Pro hand held scanners and complain it drops off randomly..its very intermittent.

All the APs are only operating on 2.4 GHZ mode - using channels 1,6,11.
IPs of the APs are in the ranges/subnets of:

The warehouses are long and open with ceilings up to approx 50 feet and are in rows.with shelving up to 3/4 of height, open shelving, some wood shelving, some metal.  the current AP deployment is that each row has 1 AP staggered for each row.  IE.  row 1 has AP near front of the row, row 2 has the AP towards the back of the row...

I have not yet run the airmagnet survey pro yet, but was wondering whats the best course of action to take.

The issue has been ongoing for over 1 year and since I came on board they asked me to look at this...
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Each WAP is in its own / and likewise servicing it's own subnet?  Are they also broadcasting the same SSID?

If this is the case, and both assumptions are correct - this would explain your drop off.  If / When a client roams to another WAP, switching to another subnet would cause any active communication to die.  Those WAPs should be servicing the same L2 network, if your clients roam between access points.
nutekconsultantAuthor Commented:
yes it is only 1 SSID

so you're saying is
lets take for example rows 1-20 in the warehouse
all the APs in those rows should be on the same subnet.  ie. 10.130.38.x?
the reason they are dropping is because of the different subnets associated with the APs

What i have to now do is determine which APs are physically located where and which L2 device they map to correct?
Yeah - what I would do if I were you, would be to create a map of your warehouse.

Then, identify which WAPs were specifically servicing the exact locations, based on MAC address or something similar.

Using that map, I'd walk around and draw out each WAPs channel / signal strength.  - Most notably where you have any overlap.  I used a free utility on my Android, when doing a site-visit a little while back, so there's no need to go all crazy on it.

Most notably, you're going to want to make notes of your channel spread - and limit as much possible crosstalk between WAPs on the same channel as you can.  If you have two WAPs next to each other, both on the same channel, it's going to cause problems, intermittent drops, etc.

Your main problem I'm suspecting though, is that each WAP is broadcasting the same SSID, which you need to do anyway...  But the fact that they're in different networks.  So, you can boil it down to when a client sees signal strength for the same SSID is better coming from a different WAP that it's currently on - it'll switch over to the new WAP.  Unfortunately, this new WAP is in an entirely different L3 network, and herein is the problem.  All communication is severed at that point until it's reestablished with the new IP address that would be assigned to the device.

That, and I bet your CAM tables for MAC addresses in your switches are nasty right now, with clients jumping back and forth.  Probably alot of unneccessary MAC updates bouncing around in your network.


So yeah - I'd take all of the WAPs with the potential of having roaming clients, and make sure they're on the same L2 / L3 network.

I'd do this prior to troubleshooting further, in my honest opinion.
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***That being said, I'm no wireless expert by any means of the word.  This is just my own experience when troubleshooting one of our campuses / with approx 30 or 40 WAPs, with users complaining of the same sorts of problems.  (intermittent connection / horrible throughput / etc.)

In my particular case, our controller wasn't separating the channels as it was advertised.  We had clusters of WAPs right next to each other all on the same channel.  Once I saw it for my own eyes in the field, I immediately went to work and reconfigured our controller to do what it was supposed to.  As it turns out, that particular option in our controller (Brocade) wasn't on by default.  Go figure.

One tiny little option, and it created a TON of hate and disconnect between users and IT.  Unneeded hate and discontent at that.

After adjusting the setting in our case, everything smoothed out and was INSTANTLY better for our users.

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nutekconsultantAuthor Commented:
usslindstrom - what app do you use on your android?
I have android as well, I can do that today...
For mine, I just used the free one 'Wifi Analyzer'.

There are a TON of other ones, probably better.  But $Free.95 is an awesome price point.  :)

nutekconsultantAuthor Commented:
excellant, thanks for this, I am going to download and get started with that.

I already have jpg. of the floorplans which have allthe APs listed and which MAC Address/IP Addresses are located where...

I will keep you posted.
Just to clarify @usslindstrom's earlier statements, it's considered best practice to have each L2 SSID map to the same L3 subnet.

I'm assuming that the W-6000 and Aruba APs interact similarly to the way other single-vendor solutions work (Cisco, Rucus, etc...), so the APs should be in either LWAP/CAPWAP mode with all of the client traffic centralizing at the W-6000.

As long as the controller is handling the client traffic, it shouldn't matter what IPs the APs have assigned, unless they're running in Autonomous or Hybrid modes.
nutekconsultantAuthor Commented:
Update - I ran AirMagnet Survey on the warehouse and 80% of the warehouse has co-channel interference, I have attached the report to discuss.
I've also examined the channels the APs are running on and they are only running 2.4 ghz on 1,6,11 with a lot of overlap
the ceilings are approx. 50 ft as mentioned, but the row heights of the racks/shelves are maybe 35 ft, and its all open from 35 ' to 50 ' so clear open space for the APs to see one another as the APs are mounted literaly right onto the ceilings, maybe a few feet under to the trusses.
I'm not seeing any attachments for some reason.

If you're in the US, than 1, 6, and 11 are the only usable channels in the 2.4GHz band.
If you're in Japan or some European countries, you can use 1, 5, 9, and 13.

My biggest question is whether the APs are running in Autonomous mode or Controlled mode. Can you attach a screenshot from the W-6000 showing how the APs are configured?
Yeah - the attached file didn't make up to to EE.

No biggie though, based on your description, I can guarantee that you're having cross-talk between the WAPs - the same problem I described above in my own scenario.

Please hit up dbright's question about independent, controlled, or even mixed-mode WAPs.  - But either way you slice it, it sounds like you've got some work to do.  :)


To add to my "make sure they're on the same L2 / L3 network" comment in your case, I'd add "channel separation" to the mix.

In my case, like I mentioned, it was as simple as "flipping the switch" in our Brocade controllers to actually listen for nearby WAPs and adjust themselves accordingly.  In your case, I'm not sure about your controller.

If, it turns out that you're going to have problems getting the 'noise' out between WAPs on the same channel - you may have to explore a couple different options...  Like turning down the antenna strength for the WAPs in the warehouse, or WORST-CASE scenario remove a couple sporratic units so you're not flooding the space with radio waves.
nutekconsultantAuthor Commented:
let me try again to attach a doc. which has the warehouse floorplan with current AP deployments

here is some more info I found out from one of the IT managers here in capitals below.
1.      Are the APs running in LWAP or CAPWAP mode?
2.      Is the controller handling all the traffic?
3.      Are the APs running on hybrid or autonomous mode?
Lightweight Mode
4. also - the different subnet issue will come to halt this weekend
We identify around 16 AP’s that can be moved to vlan that should resolve putting all devices under the same subnet.
Clarification:  The WAPs themselves don't need to be in the same subnet.  Just the SSID (if you're broadcasting the same SSID and expect that your clients should be able to roam).
I won't swear to it without a scale, but your AP density is definitely one of the highest I've ever seen.

Since you're in a warehouse environment with a metal roof, I'm going to assume this was done to try and combat multipath interference. Multipath is going to be your number one problem, and the fix is going to be to minimize each AP (and client)'s transmit power so you have as few reflections as possible.

Let's start with what you can do in the short term without physically moving the APs.
In the controller's RRM settings, make sure that both Power Management (may be called TPC) and Channel Management (may be called DCA) are both turned on.
Under your RF Groups or Roaming settings, make sure that all of the APs are assigned to the same roaming group.
Put APs 41 and 05 into Spectrum Monitor mode (or whatever Dell calls it). These are so close to the next adjacent APs that they're not going to be able to do any good as far as coverage is concerned.

For the long term, you'll likely need to reposition the APs and use a different antenna than the omnidirectional ones that come with the Aruba 125s. Airmagnet should have a planning mode that lets you pick antenna types, AP heights, etc... Here are my gut instincts on the type of antennae you need.
For the shelving areas, mount the APs on the ceilings and use a Yagi or "Dish" antenna with a conical radiation pattern. Something in the order of 0 to +5dBm gain on the +Y axis, -20 to -30 on the -Y axis, and -5 to -10dBm on the X and Z axes would be ideal.
For any office or open areas, mount the APs on the walls and use either the stock rigid dipoles or flexible "Rubber ducky" dipoles since they're pretty omnidirectional.
@nutekconsultant - Were you able to get the APs into the same subnet? How are things responding now?
nutekconsultantAuthor Commented:
hey guys, I was off on leave, but back to work as of yesterday - been backlogged - will get back onto this early next week.

Also - I noticed out firmware on the controller is  - I spoke to Aruba support - they said its highly suggested to upgrade to firmware 6.2
My question is - does anyone have a doc which tells me what the patches, upgrades were from 6.1 to 6.2?  key improvements.?

dbright deserved these points, his answers were much more specific than my generalizations.

Did you get everything worked out?
nutekconsultantAuthor Commented:
I don't know how to re-assign - I'm sorry about the mixup here.
things are improving but everything has been put on hold as there are other issues IT team is looking after, so this will not get looked at until another 4 weeks down the road.
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