What is a suitable AP for a high density location?

Collision Collapse:

Wifi is based on CSMA as a method of multiple access - old thinnet and 10mbit LAN networks used the same method.

When a packet is sent between a an AP and client device, an acknowledgement is returned to say the packet is recieved in good order. If the acknowledgement fails, the packet is resent.

When a user streams data, the packets flow nicely between the AP (router) and the client device (ipad / laptop)

When User-2 comes along and tries to send an http get request for www.google.co.nz their device will interrupt the stream of data between the AP and User-1

CSMA kicks in.
The interference from User-2 causes the packet traveling between User1 and the AP to be malformed. The acknowledgement fails.
Both devices therefore go through a process of

1) Both devices stop sending data
2) Both devices pick a random amount of time. Hopefully they dont pick the same number.
3) Each device will attempt to resend their packet. If they picked a different time, they will hopefully get their packet through.
4) Each device will continue to send more packets
5) If two packets try to be transmitted at the same time, the process begins again.

When this happens over and over and over again, its called collision collapse.
The total throughput of the AP drops to almost nothing due to all the stopping, waiting and restarting.

Now all wifi routers suffer from this. Even the best.
But some of the fancy ones like the Ruckus can do things to mitigate the damage.

So basically unless you are willing to spend thousands on a centrally managed system, your typical maximum usage through a $100 to $500 wifi router is
30 users doing nothing idle -or-
25 users pinging 8.8.8.8 -or-
18 users lightly surfing trademe -or-
1 user streaming youtube and 1 user trying to lightly surf trademe/

Once you have the wifi sorted, then your next step is to get the broadband fixed.

My suggestion is to simply buy 3 wifi routers, set them all to 20mhz, one on channel 1, another on channel 6, and the third on channel 11.
That way the client devices can be spread over the 3 access points so the collision collapse isnt so bad on each one.
Even if you just get two routers that have an "AP Only Mode" (most belkins do) and just plug those into the ISP provided router.

A school can easily run on a reasonably fast ADSL connection - i doubt your subcontractors are going to be looking at videos so you should be fine there.

A1den

raytaylor