Folks: I've been to the IEEE conferences as well and can attest to the surprising good coverage and robustness of the WLANs at the IEEE meetings. This is especially interesting in that the network is for the most part constructed when they arrive on site and walls are moved around over the course of the week (from large open plenary type to smaller meeting rooms for the working groups.
As to more than 3 channel designs, we experiment at CMU with four channels in a single lecture hall with mixed results. It was a tiered room (approx. 100 seats) and we were (beta) testing load balancing and 4 channels. The problem appeared to be that clients were jumping between APs as part of load balancing and the retransmissions were less efficient. It appeared that a classic 3 channel design improved things. As for Sean's plan, I'd suggest looking into keeping 3 channels but to try to limit the client connections to a "speed limit" (I believe you can do this with Proxim's stuff). If you set the speed to 11Mbps then that should effectively limit the range of the APs allowing for more targeted coverage. You can also look at using different antennas to effectively "paint" a certain section of the room for an AP card. Best regards, Chuck Bartel Director of Network Services Project Director Wireless Andrew Carnegie Mellon University -----Original Message----- From: 802.11 wireless issues listserv [mailto:[EMAIL PROTECTED] On Behalf Of Sean Che Sent: Friday, January 09, 2004 2:15 PM To: [EMAIL PROTECTED] Subject: Re: [WIRELESS-LAN] Wireless Networking in Large Classrooms 800 people! Wow! I once went to Internet2/Joint Tech meeting and saw similar sight, but that was about 400 people or so... John, for that large lecture hall with 250 users, we plan to use Proxim AP2000 with two radio interfaces. Four AP2000s are going to be deployed, one for each corner so totally 8 radios. In such an open and relatively small space, allocation of 8 channels seems not trivial, e.g. not possible for 1-6-11 scheme Most of the channels are going to be used . Some of the overlapping radios ( basically they are all overlapping :-P ) have to use adjacent channels. Any suggestion/experience about this? Thanks, Sean Jonn Martell wrote: > I used to be very worried about high density until I started to attend > the IEEE meetings a few years ago where there is close to 800 engineers > with laptops downloading PDFs, PPTs and DOCs. Quite the sight! I wish > there was a way to take pictures but these aren't allowed at IEEE > meetings. Worth the trip to one of their conference as an observer if > you want to increase your comfort level on high density deployments. > > Every wireless engineer has a laptop and they are all in the same > ballroom at the beginning and end of the conference. During the > conference, all the attendees are in close proximity as the large > conference hall gets broken up into a dozen smaller large meeting rooms. > > I'm not convinced that tuning the radios below the power of most clients > is a good idea and our RF research group has found that power control in > its current state is really inadequate (as a result, we aren't focusing > on power tuning in our deployment). > > To do load balancing, the trick I think at this point is to make sure > that you turn off support for the lower speeds to force roaming to the > other stronger APs. There is no standards-base way of doing load > balancing. > > What the IEEE is doing with IEEE 802.11k is an attempt to provide a > standards-based resource management information so that radios can help > tune down the power of clients (as it's done in the cell phone industry) > so that clients don't keep blasting away if they don't have to. So this > problem is getting fixed because the market needs it. I'm not too sure > if the problem is going to be fully fixed with 802.11k but Cisco, with > its "Cisco Compatible" CCX program, is doing the same today. They are > just ahead of the slower moving standards bodies but now have several > vendors supporting CCX (this list was empty last year at this time). > http://www.cisco.com/en/US/partners/pr46/pr147/partners_pgm_partners_0900aec d800a7907.html > > > Until this is widely available, directional antennas at the APs for > these special circumstances makes a lot of sense. > > For large theaters, we deployed a single AP for now but we have three AP > drops (each AP drop has 2 cable/circuits) so we can scale to 6 APs if we > need to. > > I predict the ultimate answer for high density in large rooms will be > the next generation of 802.11a possibly combined with standards-based > client radio management. In the 5 GHz WLAN spectrum there is 200 MHz of > available spectrum versus just 83 MHz in 2.4 GHz range. IEEE 802.11a is > just not there today... > > ... Jonn Martell, UBC Wireless, www.wireless.ubc.ca > > Sean Che wrote: > >> High density is a big challenge to wireless deployment. We are currently >> facing the same issue. In one of our wireless projects, we were told >> that there might be up to 250 simultaneous users ( Even worse: Did I >> mention they are all Pocket PCs with wireless cards? ) in one large >> lecture hall for class. In this kind of "noise" crowded environment, >> not only the APs will interfere with each other, the clients radio cards >> will also join the choral society.. What a nightmare! >> We are thinking of using directional antennas to help distributing the >> clients evenly; tuning the transmitting power to minimum. The problem >> is we couldn't really get a feeling how it works before we really >> install it and those 250 students really start using it ( and maybe >> complain about it. ) >> >> Sean >> >> Arnold Hassen wrote: >> >>> 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/. >> >> >> >> >> -- >> >> ------------------------------------- >> Sean Che >> Network Engineer >> Network Services >> Wayne State University >> Voice: (313)577-1922 >> Pager: (313)990-5403 >> Email: [EMAIL PROTECTED] >> ------------------------------------- >> >> >> ********** >> Participation and subscription information for this EDUCAUSE Constituent >> Group discussion list can be found at http://www.educause.edu/cg/. >> > > ********** > Participation and subscription information for this EDUCAUSE > Constituent Group discussion list can be found at > http://www.educause.edu/cg/. -- ------------------------------------- Sean Che Network Engineer Network Services Wayne State University Voice: (313)577-1922 Pager: (313)990-5403 Email: [EMAIL PROTECTED] ------------------------------------- ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/cg/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/cg/.
