(For those that are interested, I have finally written up my 2009 report on the wireless at PyCon).
I have done the wireless for the PyCon conference most of the years since we moved from George Washington University into hotels, so I have some ideas about this, which have been proven in battle — though only with around a thousand users.
One thing I hear a lot of people talking about in this discussion is “open air coverage in a ballroom”. One theory I operate under is that the ballroom is NOT an open air environment. Human bodies soak up 802.11b/g and 802.11a quite nicely.
Here are some of my thoughts, but more details are available in my conference reports if you search google for “pycon wireless” — the tummy.com links are what you want.
I use just the non-overlapping channels, and spread the APs out. For 802.11b/g, I run the radios at the lowest power settings. For 802.11a I run it at the higest power setting because we have so many channels.
I try to keep the APs fairly low, so the bodies can help reduce interference between APs on the same channel.
I set all the APs to the same ESSID so that people can “roam” to different APs as loads (number of associated clients) go up or coverage goes down (more people coming in, etc).
Lots and lots of APs. The first year we had the hotel do the networking, they eventually brought in 6 APs, but they had started with only a couple. Despite that we had told them that we would be heavily using their wireless. But we also had other problems like the DHCP server giving out leases with a gateway in a different network than the address. (Calls to support resulted in “I’ll just reboot everything.”).
We are running relatively inexpensive D-Link dual-radio APs, costing around $100 or $200 each. We just haven’t really had the budget to buy 20 to 40 of the $600+ high end APs. These D-Link APs have worked surprisingly well.
In 2009 we had a hell of a problem with netbooks. Something about the radios in these just stinks for use at this sort of conference. I’ve heard reports of people putting Intel wireless cards in the Netbooks and getting much better performance. At PyCon 2009, my netbook couldn’t get a reliable connection after the conference started, but my ThinkPad had no problems. I heard similar reports from people with Mac and other “real” laptops, but the cheapest hardware just was not working.
I have NOT done anything with directional antennas. I was expecting to need them, but so far it has worked out well enough.
Most hotels cannot provide enough bandwidth. Don’t worry though, there are lots of terrestrial wireless providers that can provide 100mbps. I’m not talking about the places that run 802.11g from some tower, but people with real, serious radios and backhaul to cope with it.
Over the last several years we haven’t really had much in the way of wired ports, mostly because of budget and volunteer effort required to cable all those locations. In 2010 we expect to have quite a few wired ports. I like the idea of wiring every seat for wired, but I would doubt we’ll be able to cover even 10% simply due to the effort required to wire and maintain such a network. Getting people off the wireless is great.
Getting people off the 802.11b frequencies is good as well. Most people talking about since Joel has brought it up have been saying things like “3 non-overlapping channels”, which is true for the 2.4GHz spectrum. However, we have seen a HUGE move towards the 5.2GHz spectrum. The first year I ran the network (2006?), we had around 25% usage. In 2008 we had over 60% in 5.2GHz.
So, yes, running wireless with thousands of people requires some thought. But, giving it some thought seems to have resulted in a fairly high level of satisfaction.
Sean