We've also had great success with large lecture halls. The College of Engineering initiated a tablet PC requirement for all incoming freshman. The thought was that the tablets would be a great classroom resource for the students, replacing pad and paper. This led to them experimenting with collaborative instructional software (whatever the lecturer writes on the virtual whiteboard or presents a slide, the content gets pushed to each student where they can make annotations, replay it later, etc). Early trials where ghastly failures (many reasons for this, both application and network inefficiencies) where the latency was so bad that students would abandon the tool and revert to pencil/paper. Last year, the College trialed a SW package called DyKnow which was very efficient from a network standpoint. They then offered up a 270 student freshman Engineering class to serve as a guinea pig, and asked us if we'd help them make it work.
We took the opportunity to develop parameters to tweak our Cisco IOS AP's (similar approach as Lee, pico-cell architecture, dropped power levels, denied low data rates, careful placement of AP's, etc.) and achieved great results. For this room we were and still are using 4 abg WAP's. One of the biggest difficulties encountered was balancing clients among not only all 4 of the WAPs, but also balancing them between the 2 radios on each WAP. (most if not all clients are dual-band) We also held a bake-off with the big 3 LWAPP vendors. The results showed that these solutions were no better and sometimes worse than what we could achieve with manual tinkering of our IOS AP's. In this environment, we are using 4 abg WAP's and one of the difficulties was balancing clients among not only all 4 of the WAPs, but also balancing them between the 2 radios on each WAP. In general I was disappointed with the client load balancing algorithms, what little they could reveal to us. We came to a decision that the cost of moving to LWAPP outweighed the benefits at this time, even with the added burden of manually fine-tuning each AP. I'd rather not be in this position, but I haven't found a controller system that meets our needs. As the collaborative tools get more bloated and the bandwidth needs increase, I'm anticipating we'll run into problems using this manual approach. I think 11n and eventually 11k may provide some relief, but for now our faculty and students are very happy with the performance. Steven Lee Research and Development Communications Network Services Virginia Tech 1770 Forecast Drive Blacksburg VA 24061 540-231-7957 -----Original Message----- From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Lee H Badman Sent: Wednesday, April 23, 2008 8:07 AM To: [email protected] Subject: Re: [WIRELESS-LAN] many clients, one room Many moons ago when we used Cisco IOS APs for our new WLAN, we would create picocells (knowing that the term means different things to different people) by turning down the power to 1 mW, and also adding an attenuator between AP and antenna to further restrict output power. Then we'd basically fill large auditoriums with 3-5 of these, depending on the size of the venue. It worked wonderfully for supporting a couple of hundred "casual users" on 802.11b and then g. Fast forward to LWAPP. We still provision multiple APs per large auditorium, but these rooms are seldom islands- they also are typically surrounded by other APs in adjacent areas(laterally, above, and below) where they further share cells. It was a leap of faith letting RRM decide on power and channel, but so far we have yet to be burned (that we know of). But... we do not "do" voice over the WLAN formally. Or multicast over wireless. And the typical Internet-delivered video stream for the "casual/typical" client tends to be around 500 kbps, so we're not feeling a lot of pain even when 150 users are on a small handful of a/g APs, and thus far most traffic is to the Internet where we have per-user caps anyway. Then factor in that 1/3 of these are actually using 11a and the remainder are on 11g on our dual-band APs. And at least half of all are using some version of CCX... And we still have the occasional 11b device pop up (around 2% of all of our 5000+ simultaneous clients), and we let them. And there are sometimes classroom response systems in use in 2.4 GHz in these same spaces. It gets fuzzy in our "real world", but we rarely (as in almost never) hear of dissatisfaction with the WLAN throughput. In fact, as silly as it sounds, we get written compliments from visitors on occasion on how well our WLAN performs. Long winded answer to a simple question- but we are basically applying simple common-sense design for capacity and mostly ignoring much of the hysteria and hype that comes from vendors volleying the finer points of how they one-up each other on wireless, and doing just fine (for now) given that our day-to-day "lab" is reality. -Lee Lee H. Badman Wireless/Network Engineer Information Technology and Services Syracuse University 315 443-3003 -----Original Message----- From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Frank Bulk - iNAME Sent: Tuesday, April 22, 2008 11:49 PM To: [email protected] Subject: Re: [WIRELESS-LAN] many clients, one room Can anyone on this list comment on their "dense" experiences with vendors other than Meru (and Xirrus)? I know I may appear to be buoying Meru in this thread, but it's only because I haven't heard a higher-ed using another vendor talk about their own good experiences. Regards, Frank -----Original Message----- From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of Frank Bulk Sent: Monday, April 14, 2008 2:52 PM To: [email protected] Subject: Re: [WIRELESS-LAN] many clients, one room John's comments reflect almost exactly what I heard two years ago. Would love to hear on this list from other shops (Aruba, Cisco, Colubris, Symbol, Trapeze, Symbol) what their experiences and configurations are in similar circumstances. Frank -----Original Message----- From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[EMAIL PROTECTED] On Behalf Of John Center Sent: Monday, April 14, 2008 10:48 AM To: [email protected] Subject: Re: [WIRELESS-LAN] many clients, one room Hi Clint, The AP208 have 2 radios, 11a & 11b/g. We have the laptops set up to prefer 11a, so the bulk of the connections are 11a. MathCAD is installed locally on the laptops, but the size of the student files vary - probably comparable to a Powerpoint presentation. We used to do this with Cisco AP1200s & had constant complaints. No more. We had the same problem at exam times at our Law School. No more. Like I said, we are very happy with the Meru products. HTH -John Ringgold, Clint wrote: > Can you please give us more information in terms of how the APs and > Laptops were setup. > > I'm no math major and on a bad day I have trouble adding (don't laugh). > Anyway, I'm just wondering if it was setup so you have > 54+54+11+11=130/250(users)=.52 or 54+54+11=119/250(users)=.476. I am > not implying a thing. I'm asking this just for my clarification. > > It sounds like the software may have been on the laptop and/or only the > answer or very small packets were saved to/from a server. If it is > "designed" to work with little bandwidth (like Citrix) then that is > great. I'm just saying it is a difference. > > > -----Original Message----- > From: The EDUCAUSE Wireless Issues Constituent Group Listserv > [mailto:[EMAIL PROTECTED] On Behalf Of John Center > Sent: Monday, April 14, 2008 8:28 AM > To: [email protected] > Subject: Re: [WIRELESS-LAN] many clients, one room > > Hi Don, > > We are a Meru customer & we've had great success with their system in > our large lecture rooms. On Friday, we had 250 Engineering students > taking an exam, which required MathCAD, on 2 Meru AP208s. The exam ran > flawlessly. > > HTH > > -John > > > Don Wright wrote: >> I know this has been talked about and debated on this list > before, >> but what are people doing today when faced with a request like the > need >> "for 100 students simultaneously downloading a powerpoint > presentation". >> Recently there was discussion on MCA vs. SCA vendors and how each >> handles this worst case scenario. Since we are an MCA (Aruba), I'd > be >> interested in hearing what others have done or are planning for large >> classrooms and auditoriums. >> >> -- >> Don Wright >> Network Technologies Group >> Brown University >> >> wire --- less, wi-fi ))) more >> ********** Participation and subscription information for this > EDUCAUSE >> Constituent Group discussion list can be found at >> http://www.educause.edu/groups/. > > ********** > Participation and subscription information for this EDUCAUSE Constituent > Group discussion list can be found at http://www.educause.edu/groups/. > > ********** > Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
