Wireless in Libraries

[Cary Gordon]

25 users per AP is a great goal, but it is impractical in many scenarios. The technical limit is 2007 concurrent associations per AP, and that limit applies to each transceiver in a concurrent multiband AP.

Caveats abound. If you had an AP that was actively associated with 4014 devices, there would likely be a panoply of bad things happening, and you would likely be down to teletype speed.

Moving into the practical realm, real-world professional APs, like those from Meraki (Cisco) can handle 256 connections — 128 per radio — although quality goes down geometrically at higher load. One big question is what will your connections be doing. With your APs fully loaded, streaming individual HD videos might be pretty nasty, and your VOIP connections might seem to be in Klingon. Web browsing, being asynchronous, can work.

Fun fact: Ruckus is covered Maracana Stadium in Rio (76k seats) with 217 APs. Making this work required hands-on tuning of each AP and a very concentrated, ongoing effort to get folks to use the 5GHz band.

I think that the bottom line is that you must use professional equipment, and, if at all possible, have it installed by trained professionals.

Cary

> On Aug 9, 2016, at 10:24 AM, Jon Knight <J.P.Knight at LBORO.AC.UK> wrote:
> 
> On Tue, 9 Aug 2016, Bill Coffey wrote:
>> We have a simple wireless access connection running 4 access points with a DHCP server.
>> We are having an issue with slow connections or access. From my statistics I see we have an average of 150 patrons access the wireless during the day.
> [...]
>> 3.       How many access points do you have?
> 
> I can't help on the TWC aspects, but an average of 150 users spread over 4 APs might well be your problem, especially if those users aren't evenly spread (so one or two APs is taking the bulk of the load).  There's lots of nuances to WiFi sizing and coverage, but a rule of thumb is to aim for around 25 users at most on each radio on each AP - fewer if the users are all doing bandwidth intensive tasks such as video streaming.
> 
> You might also find that if you're covering large areas with these 4 APs you'll have low bit rate "distant" connections using up comparatively long periods of time.  If you haven't already done so, you might want to turn off slower bit rates to ignore these distant, slow clients.
> 
> In my experience, libraries also have additional issues in that metal shelving can act as wave guides for the microwave signals used in WiFi comms.  This means that they can both act as shields attenuating the signal in some places whilst also causing it to appear where you don't necessarily expect it.  We tend to aim to cover areas around the edge of the building and in the large "open" (no shelving) areas on each floor.
> 
> Hope that helps,
> 
> Jon
> 
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2016-08-09