Wireless Access

Hello,

 

This is just a quick question regarding placement of the AP105.

 

We have a site running the Aruba 650 controller with various AP105's scattered around the building (the building in question is a school). I have noticed that whoever installed the AP105's, mounted each one above the door on the wall, on the inside of each classroom as you walk in. When I queried this, I was told that it was done that way because (to quote) "that is just the way we do it". Having spent some time reading about the AP105, there is some information saying that it does support wall mounting but the preference is ceiling. I don't think the placement of the APs in this particular site was done via a survey or RF plan, I think it was just guess work to be honest. Almost like whoever did the install just assumed that the wireless would work fine, regardless of where the APs are located, because they are all cabled via Cat5e and also the fact that the Aruba kit works so well.

 

I just wanted to know if the placement of the APs could possibly be a cause of poor performance? I have read the Aruba Site Survey guide, and it does describe the various patterns that an AP radiates along with some useful pictures, which makes me wonder if the APs might well be located in the wrong place. This particular school have reported some issues with the performance of their wireless in general, and whilst it could be one of many problems, I thought it best to start with the basics and try to identify whether or not the APs are located correctly.

 

If anyone can advise or throw in their 2 cents worth, it would be appreciated as I am a newbie to the Aruba world.

 

Cheers

The AP-105 has down-tilt omni directional antennas.  That means that most of the energy is focused in front of the AP.  If you mount it on a wall, coverage would be spotty directly below the AP and there would be virtually no coverage behind it.  It is really not meant to be wall moutned unless you are mounting it on external walls (facing inward) AND dont need coverage directly beside the AP.

 

I don't know your site or configuration, but if people are complaining about coverage issues, I would suspect the placement of the AP is the most likely suspect.

Hi,

 

Thanks for the reply.

 

I spent some time at the aforementioned site earlier today, and looked at the AP placement. I think they have been wall mounted because the ceilings in each classroom are sloped, none have a flat ceiling. The ceilings also have wooden support beams on each side that span the length of the room and these are also sloped (and quite large). It looks like whoever did the install must have figured that the easiest place to mount the APs would be on the wall just above the door inside each classroom. I think the dimensions of each class is approx 20(L) x 15(W) feet.

 

Although the placement on the wall isn't ideal there doesn't appear to be a loss of coverage within the classrooms, as far as I could tell whilst walking around with a laptop. I realise that I am relying on the wifi chipset of the laptop and not a dedicated tool such as WifiSpy, but it appeared to be useable.

 

I think my next step is to look at the laptops that are in use in school as the majority appear to be 802.11g capable (at best). The teacher told me that when the problems with performance occur, it is usually when they logon to the network (via Active Directory), some of the laptops don't map network drives, but it isn't the same laptops each time that don't map drives, it can be quite random, if that makes sense? The number of laptops used in a given class at one time would be approx 15.

 

I think my next step is to figure how many clients an individual AP-105 supports. I know the Aruba controller does some pretty clever stuff to control and manage the APs, I just don't know what they are in any detail, apart from skimming over some of the PDF guides on the main Aruba site.

 

Thanks again, I am sure that I will post again when I get somewhere.

 

Cheers

 

I don't think that positioning AP in such small space is really a issue. And 15 clients per one AP shouldn't be either.

 

Do the network drives map trough logon script? What kind of authentication do you use? Other things I would check if these computers are actually connecting to AP in another classroom and get poor signal. Dropping 1-2Mbits rates from use could help for this. Also non-wlan devices using 2.4Ghz like DECT phones or cheap-ass wireless cameras etc can easily destroy  wlan performance (btdt, sometimes only solution is 5Ghz), but you need spectrum analyzer to see this. 

Hi,

 

The authentication in use for logging on to Active Directory is kerberos, and the clients do map network drives via a logon script. I have noticed that on the 650 controller there are also some interfering devices, so I will take your suggestion on board and check whether there are any cordless phones etc, and also check that the clients are hitting the correct AP.

 

I am due to visit the site this morning, so I will check a few more things whilst there.

 

Thanks for the help.

 

Cheers

 

 

Do you use user/computer/certficate authentication? If you use user authentication, the wlan activates only after you log in and the network may not be ready when the logon script is run. 

Basically, users just logon to the wireless laptops the same way they would if they were logging on with the laptop "wired" to an RJ45 socket. They have a user name in Active Directory, type it in at the logon box, then the drives are mapped via a logon script. This does work ok on most laptops, it is just one or two at random that don't always map when they should.

 

I think the problems with the site go deeper than just drives not mapping, there are other issues that I have discovered, but for the time being I am just checking the laptops one by one to ensure that they can access the wireless network individually, and then I am going to look into the actual wireless setup that is in place.

 

Cheers

I meant wireless network authentication.

Hi,

 

I think it is WPA2-PSK

 

Cheers

Finding a contractor to install AP's can be a pain, I had one that mounted 105's outside, then got them relocated inside with 1 wall mounted and the other flat facing upwards, not even close to where I said to install them, or the put them up in the false roof facing upwards. VisualRF will provide some better indications on the area covered and might give you a better idea of the area covered. On the last install, while I didn't like the placement of the AP's, I found the coverage acceptable, it seems one vertical and one horizontal balances out the area too cover about 80 sqm footprint in an open area. End users are not data heavy, RF guns, so low data rates are acceptable.