I agree. Also, upgrade to 802.11 a/b/g/n APs, preferably with gigabit uplinks. The 1240 AG are a/b/g with a single 100 meg uplink.
Several years ago, we moved from fat AP 1240G ( 802.11b.g only) APs to an Aruba 802.11 a/b/g/n AP system. The users immediately noticed improvement with more client bandwidth and the intelligence of a controller based system. You did not say whether your APs are fat or thin, but I believe I read where Cisco is discontinuing support for thin 1240s in their controller software. Bruce Osborne Wireless Network Engineer IT Network Services (434) 592-4229 LIBERTY UNIVERSITY 40 Years of Training Champions for Christ: 1971-2011 From: Voll, Toivo [mailto:[email protected]] Sent: Thursday, November 10, 2011 12:54 PM Subject: Re: Access points with very low performance when multiple users connect their computers at the same time. Additional features that are helpful are ones that help dual-band clients prefer the 5GHz spectrum (Cisco and Aruba have their own names for this), and turning off all the low data rates so that air time isn’t destroyed by a few smart phones or bad clients hanging onto 2 mbps rates. Depending on budget and layout, you can also try to RF-engineering with directional (patch) antennas and such, to control cell size and shape. Toivo Voll Network Administrator Information Technology Communications University of South Florida From: The EDUCAUSE Wireless Issues Constituent Group Listserv [mailto:[email protected]]<mailto:[mailto:[email protected]]> On Behalf Of Coehoorn, Joel Sent: Thursday, November 10, 2011 12:31 To: [email protected]<mailto:[email protected]> Subject: Re: [WIRELESS-LAN] Access points with very low performance when multiple users connect their computers at the same time. Your problem is probably air time density. The issue is that you only have 3 non-overlapping channels to work with in the 2.4Ghz space, most users won't have 5Ghz-capable laptops, each channel only supports about 25 clients from a practical standpoint, each access point is likely only listening on one specific channel, and you have up to 400 users trying to connect all at about the same time. That's just not going to work. Things get better a few minutes after a class starts because some students will just give up, and most others will settle down to only use air time only in short bursts, as they load and then pause to read pages. The typical solution is turning down the transmit power, such that signal for each access point does not leave it's own classroom, and then add access points to each classroom such that you're listening on more of the available channels within the rooms. The goal is to reduce the cell size (and therefore number of clients) served by each access point, and increase the available channels. You can do this by adding access points, or by getting single access points with multiple independent radios that are capable of using the additional channels simultaneously. Even here, you'll likely still have issues as many of the laptops will not turn down power to their own radios and still clutter up the air space. It would be like trying to listen to the professor if most students in the classroom were also having conversations among each other at their normal speaking volume. As for distributing traffic, there are different load-balancing options out there depending on your vendor. But even with generic thick access points you'll see quite of bit of load balancing happens naturally, without you having to do anything special so encourage it. You ought to be able to just add the access points without needing to do much of anything for load balancing. Joel Coehoorn IT Director York College 402.363.5603 On Thu, Nov 10, 2011 at 11:09 AM, Ethan Sommer <[email protected]<mailto:[email protected]>> wrote: With almost any manufacturer you can set a max number of clients per radio. You could set the max per radio to 25ish and put (capacity of classroom/25) APs per classroom. On 11/10/2011 10:54 AM, Luis Fernando Valverde wrote: Hello, we have four adjacent classrooms (two in front of two and 5 meters between each one) with capacity to 80-100 students each one. Each classroom has its own Cisco Aironet 1240 AG Access Point. When all the students inside the classroom connect their computers to the wireless network, response time behaves very slowly for several minutes, until the traffic network stabilizes and reaches a better performance. We have tested other AP including Ruckus (802.11 b/g/n) and the problem remains. We could install two AP by classroom, but we would need to distribute the connections between each one. Does someone know a solution without having to use different SSIDs to distribute traffic among multiple access points? Does someone have any suggestion to solve this issue, including other access point manufacturer? Any comment is welcome. Thanks, ----------------------------------------------------------------------------------- Luis Fernando Valverde Director de Tecnología de Información y Comunicaciones INCAE Business School Tel: 506+ 24 37 23 38 www.incae.edu<http://www.incae.edu> ------------------------------------------------------------------------------------ ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. -- Ethan Sommer Associate Director of Core Services Gustavus Technology Services [email protected]<mailto:[email protected]> 507-933-7042<tel:507-933-7042> ********** 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/.
