What's the maximum number of wifi connections for a single WiFi router?

We've got a Draytek 2829VN Wifi router and I'm wondering how many concurrent connections I should expect a router of this kind to cope with? We are looking to connect 60 iPads!

I'd also be interested in knowing what might happen when it starts to reach capacity?

Not looking for details specifically for this model, but in general.

Thanks!

UPDATE

Thanks for everyone's help!

We ended up going with 3 wired Cisco AP's, sharing a single SSID across 3 channels. The venue already has WiFi running across channels 1,6 & 11 (the default it seems) so we've opted for channels 3, 8, and 13 which seems to be working very well, with around 20 iPads per AP.

The iPads then picked up the signal almost immediately, something they were taking in excess of 2 minutes to do when running on channels 1,6,11 due to interference.

Lesson learned : don't assume that setting up WiFi for large numbers of people is easy!

Solution 1:

While Oneiroi's answer starts to get you there. There are a few flaws that deserved more than a comment on his answer.

First, the bandwidth you are actually contending for isn't the back end ethernet link, but the wireless link speed. So on a 54 mbps router you would be contending for that 54 mbps. At 60 clients that would be about 900kbps each, not counting TCP overhead, counting TCP overhead you are already down to ~720kbps.

Secondly, you still have to deal with signal strength issues, which depending on your location could greatly effect throughput.

Thirdly, you have to deal with interference between those 60 radios all trying to broadcast. Years ago when I was working on planning an 802.11b wireless network the engineer we talked to said the rule of thumb was about 10-12 clients per AP for best performance, you can probably move that up to 20-25 (pure off the cuff number)with today's newer technologies. But that still doesn't get you to 60.

I would suggest that you take a look at some pure Wireless APs (not routers) and do a site survey to find the optimal placements for them.

Solution 2:

Concurrent connections are dictated by 2 things, bandwidth & resource,

On the resource front it would be best to ask the vendor, the cpu & memory of he hardware could be a limiting factor in the supported concurrent connections.

Bandwidth is the major limiting factor, whilst you may connect @ 54mb/s remember if you users are contenting with 50 others all over the 100mb/s Ethernet attached to the access point their actual available bandwidth becomes 2mb/s.

As you start to reach capacity you will find:

Bandwidth: The Ethernet connection is always transferring the maximum available for the connections (i.e. 100mb.s)

Resource: assuming someone isn't attempting to crack your network by spamming de-auth packets you will see a lot of "broadcasts" from the AP, as it tries to reconnect with dropped clients.