Wireless laptop trolleys - How do you do it?

[jonathan.lees]

This must be the biggest burden in my job. Our school was built centuries ago before even electricity was around! Our walls must be 3 feet thick which makes wireless barely usable. Also we have 3 floors. We have 30 laptops for lessons on two trolleys. We have to push them to the lesson and distribute the laptops to students. With the laptops are 4 access points, I have configured them for MAC address access only so there are 8 laptops allowed on each one. The AP's then connect to a gigabit switch onto the network. Logon times suck and the laptops performance is very poor. I'm looking to improve on this and would like to know if there's a better way.

[georgebush]

When I strarted at my school they had about 45 laptops in use in a single room, luckily they'd invested in Cisco Aironet APs so that side of it was reliable. The laptops where terrible though, battered and generally crap.
The main problem I found was that the previous team hadnt actually installed any software on the laptops they were downloading everything off the server and so could take upto 15 minutes for the whole class to logon even though there were 7 APs in the room.
I've since reimaged the lot with everything local and the entire class can logon in a matter of minutes now and the laptops are alot more stable in general. The bottleneck now is our terrible network, unmanaged switches at 100Mbps.

[jonathan.lees]

The only thing that is downloaded from the server is the students start menu, redirected via GPO, sometimes it fails to download and the student has to logoff.

[maniac]

On all our network machines, the start menu and desktop icons are downloaded to a folder on the machine at startup using a VBS script. In GPO they are re-directed to these local locations. I found this a useful change as it stopped the start menus and desktops disappearing when the wireless signal was lost.

We also run a mandatory policy which is cut down to the absolute minimum necessary to make logon times as quick as possible. They are still very slow on the wireless network, but better than they were last year.

The only way I've found to speed up the login to a super quick level is to use a local policy, as it's the time taken to download the policy that slows things down so much in my experience.

I don't know what make access point you're using, but we've found Cisco ones to offer the best reliability for large groups of laptops. We have 30 laptops running though a single cisco access point in a couple of locations and the performance although slow, is bareable (1m 30s logon time when a lot of machines are logging on at once, down to 30s when the machine has the access point to itself.

Running 4 access points could be causing some of your problems, as you won't achieve proper channel seperation with 4 of them in the same room. They will all interfere with each other a bit no matter what channels you choose. I would suggest using just 3 APs maxinum, and use channels 1, 6 and 12 which are far enough apart to prevent interference.

Hope that helps,

Mike.

[strawberry]

I'd strongly agree with the poster above. 4 aps will almost be almost certian to cause a problem.

[jonathan.lees]

I'm using 3com AP's, I know their not the best but what I can afford. I'll remove one of the AP's and give that a shot, I don't suppose you'd share your vb script for saving start menus locally?

thanks

[strawberry]

remove one of them, and change the channels on the remaining 3. One to channel 1, one to channel 6 and one to channel 11.

might also be an argument for using one ssid and remocing the mac authenticion.

[eean]

So you've just got MAC address filtering to force the laptops onto the right AP? (i.e AP1 has the Mac addresses for 8 clients, AP2, for another 8 etc..)
I'm guessing that the reason why you have 3 APs is to provide more capacitiy rather than extend area.

The client will always try to connect to the AP with the strongest signal (even if all 3 APs are in the same place, one will be slightly louder than the others).
It then takes quite a long time to be refused access via MAC address filtering. So it'll then try the next AP, and will take another 30 seconds to be refused a connection. Depending how the client is configured, it may also keep trying to connect to the loudest AP.

- Check your APs to see if they can pool together (the Dlinks can do this at a VERY basic level). So once AP1 has 10 clients, it will force them onto AP2.
Or (and I wouldn't normally recommend this), give each AP it's own SSID. Have each AP a different channel, as already suggested. Then configure each laptop to connect to either AP1, 2 or 3.

If you have only 8 clients on 1 AP you shouldn't really be having problems (Ours can handle 15 no probs) so something else must be wrong. Also, we have thick old Edwardian walls and the signal goes miles. Its the newer parts of the building with thin walls and steel frame that have rubbish signal.

[SimpleSi]

One for vote for 3 separate channels and 3 separate SSIDs (and don't use any encryption until you are happy with performance )

regards

Simon

[jonathan.lees]

So you've just got MAC address filtering to force the laptops onto the right AP? (i.e AP1 has the Mac addresses for 8 clients, AP2, for another 8 etc..)
I'm guessing that the reason why you have 3 APs is to provide more capacitiy rather than extend area.

that was the idea, also I have 4 different SSID's each on different channels but not as far apart as suggested, I think they are something like channels 2,4,6,8. The laptops are already configured to connect to the appropriate AP, I put the MAC address filtering on to ensure that they do just that. I'm gonna look into buying 3 better AP's , the 3 com ones are a bit old and basic now.

Has anyone gone down the route of installing a Wireless switch?

[Ric_]

I have a trolley of 30 laptops and use a super-special BlueSocket managed wireless infrastructre... I too have ridiculously thick sandstone walls to compete with.

The reason that my laptops are successful though is that they are simply used as thin client access devices so the data moving around is very limited. I use Citrix but it is certainly possible to do it with vanilla Terminal Services quite cheaply.

[maniac]

I don't suppose you'd share your vb script for saving start menus locally?

thanks

I'll post it on Monday It's a VBS script that deletes the existing folder hosting the local icons, copies over a fresh copy from the netlogon share, then runs an XCACLS command to double check the security settings are correct so students can't write to the folders. I've also included a function that will look at the AD container of the machine, and copy over custom icons where necessary so for example, only my music PCs get the shortcuts for Cubase, and my SEN computers get the shortcuts for the SEN software on the desktop.

Because they are refreshed at each re-boot, if students do somehow manage to mess them up, it's only a temporary change. As it's only copying shortcuts it only takes a few seconds for all these scripts to run, so it doesn't adversely affect your startup times. It can speed up your login time a little, but the main thing it does is stop wireless laptops from loosing their start menus and desktops if they loose the wireless signal.

Mike.

[frankybaloney]

The way we have got around the problem is to buy laptops which pick up the A band signal.

Then mount an access point which only gives out a A band signal. Connect the access point to a network point in the room and voila! you have a room full of laptops which do not interfere with other access points in the college that run on B/G bands

If you need more info then just give us a shout and ill explain it to you more clearly.