We are designing two new 200 seat classrooms that will be adjacent to one another. Discussion is focussing on whether we should hardwire or go wireless. Functionally we must be capable of simultaneous networking which means 400+ simultaneous links. Is this doable with wireless? Thanks for any help Arnie Hassen West Virginia School of Osteopathic Medicine ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/cg/.
I've seen a few "it might work" suggestions, but I don't think anyone's actually gotten 400 simultaneous wireless connections working in a single room, and I don't think it's physically or logistically possible.
First of all, the 802.11 protocols theoretically allow 255 connections per access point, but accepted wisdom is 20-30 per point. That means you need 20 APs for the room. You have 3 available wireless channels, so you'd have to figure out a way to spread the points so they don't overlap. In an open space this simply isn't possible even if you reduce the transmit power on the APs and cards to 1mW. Also, at 20 connections per point the effective bandwidth of an AP is about 1/2 of its nominal bandwidth, so you're looking at about 5Mbps for 802.11b, about 25Mbps for 802.11a or g. That may be enough bandwidth for casual web surfing, IM or email, but isn't enough for networked file access, file sharing, or running applications from a file server. It's also exacerbated by the fact that wireless is a collision avoidance technology instead of collision detection. Basically, in contention, stations will transmit very infrequently, and reduce available bandwidth further.
We, as IT professionals, have to do a much better job managing expectations. There's no way any wireless infrastructure will perform like a 100Mbps switched wired network, and this will become critical in classrooms for any serious amount of data (I didn't even mention videoconferencing, or multimedia applications.) If your administration or faculty think wireless equals wired in terms of usability, especially in the density of people and usage of a classroom, you need to clear that up for them. Sure, it seems the same to them at home using their DSL connection or printing to their network printer, but that's not the same as an entire class attempting to watch a video or collaborate with data. If you plan on using computers in the classroom, and are doing more than sporadic access to the Internet, you need a wired infrastructure in the rooms. We've learned this lesson and are now advocating and planning to rewire several rooms that we thought would be "just fine" with wireless.
--Mike
Mike Richichi Director of Computing and Network Services, Drew University mailto:[EMAIL PROTECTED], http://users.drew.edu/mrichich/
********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/cg/.
