John - We have a number of high density classrooms across our campus, and there are a number of things that I would suggest. The first is to not let your controllers control the signal. You are much better off with statically setting your channels. At least in the Aruba world, when APs are directly in line with each other it can mess with the algorithms used to make power and channel decisions.
I'm also curious how many 2.4 GHz radios you have on? If they are all turned on, you are just stabbing your self in the foot, repeatedly. I would turn off all but three of your 2.4 GHz, and turn them up a little louder. I'd also avoid having a 2.4 GHz radio on near the door. Not good for sticky clients. I'd be curious how this would help your situation. The thing that I would worry about with leaky coax antennas, especially with multiple radios on, is that you are going to have a lot of cross talk interference in the space. You are also going to start messing with the MIMO and lose some performance there. I would personally try to avoid it. ---- Charles Rumford Network Engineer ISC Network Operations University of Pennsylvania (p) 215-746-2808 (c) 267-398-7939 On Jun 12, 2013, at 3:05 PM, "Watters, John" <[email protected]> wrote: > > We are having problems in a significant number of large lecture halls with > being able to provide adequate wireless coverage to handle what the > instructors want to do – have everyone connect to some site and do the same > thing at the same time. Of course this can be problematic from the server > end, but often the server is fine (particularly when it is local), the > connectivity to the wireless clients in the bottleneck. > > Most of our large auditoriums of this type have concrete floors built on > grade (thus no mounting APs under the floor), are tiered with fixed seating, > many have fixed tables, and most have a ceiling height of 25-30+ feet at the > front and maybe as little 12’ at the back. > > Ceiling mounting is problematic – too hard to service above the seats and at > the high end, directional antennas are “too ugly” to be acceptable, and > integrated antennas provide too large of a coverage area to keep client > counts/AP reasonable (especially in the 2.4 GHz range where 75% of our usage > currently occurs). > > Wall mounted units (which we use now) do not keep client counts/AP down to a > level that we would like (e.g., about 15 users/AP) and coverage in the center > of the room is poor, mostly caused by an unfettered signal going all the way > across the room & spreading out as it goes. Our Cisco WiSM controllers try to > balance the signal strengths, but that then leaves a coverage hole in the > middle of the room. With only three 2.4 GHz channels to use, this is very > messy. The folks using 5 GHz are much happier. > > Under table mounting could be very good with an AP placed to cover maybe a > 10’ circle. But, current APs are way to thick to be unobtrusive. I had hoped > the Motorola in-wallbox unit would be small enough for this application, but > their 100 Mbps uplink and single radio was a showstopper for us. Why can’t > the WiFi folks make an AP the size of a cell phone?? Or, even two cell > phones?? The cell phone folks can do it and pack a phone & other goodies into > a very small package along with their WiFi radio. I’m not looking for great > range here, just small with good service attributes. > > I have thought about using leaky coax antennas fastened to the bottom of the > table tops and connected to an AP at each end of an aisle (may also need on > in the middle). Small size would not be too intrusive and hopefully not too > prone to mutilation. I could even put multiple cables in parallel under the > table tops. > > My Cisco sales rep had some experience with this type of antenna when he did > some work for an underground mine. > > > > My questions to the group are: > > (1) Has anyone ever used leaky coax antennas in any application even remotely > similar to this? Was the experience good or bad? > > (2) Does anyone have any vendor recommendations for purchasing leaky coax > antennas? > > (3) Is this technically viable for both 2.4 & 5 GHz applications? > > (4) What am I missing? If this is a viable solution, why can’t I find out > anything about it from a Web search? > > (5) Does anyone have any very good or very bad experiences with deployments > in this type of venue that they would be willing to share? > > > > Thanks. > -jcw > <image001.jpg> > > > > John Watters The University of Alabama > Office of Information > Technology > 205-348-3992 > > > ********** 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/.
