large venue WIFI

Unanswered Question
Feb 13th, 2009

What are the best AP's to use in a concert hall type venue with a large nunmber of client users and how do I make it so that they are spread across the AP's and not just filling certain ones up?

I have this problem too.
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Scott Fella Fri, 02/13/2009 - 05:15

Not knowing how the venue is and really how big, it would be pretty hard to answer your question. If you think you will have alot of multipath, then maybe look into the 1252 or the 1142. Again, is it the best ap you are looking for or maybe it should be what antenna should I use. One thing to understand is that many users out there have only 2.4ghz enabled for iphones, etc. So now it comes down to how many 2.4ghz radios can I have in an area without having too much interference. This can only be determined by a wireless site survey. The 5ghz side, you have more than 3 channels to play with so you can have more radios in a given area than you can in the 2.4ghz side. Also, the mounting of the ap's.... is it going to be 50+ feet up in the air or lower... this will affect your signal propagation. There is too many things to look at to see if this is even possible, especially if you plan on supporting 100+ devices.

terminalvelocity777 Fri, 02/13/2009 - 06:28


The venue is the size of a movie theatre but used for concerts and will have maybe 200 users across the area. The AP's will be mounted about 20 feet high, my question was more how do I get the users in the area to spread out across the AP's the main clients will be on 2.4ghz. I was thinking of using 1240's as I have heard they give better RF coverage etc even on a 802.11g network has anyone used them for 802.11g in partyicular?

terminalvelocity777 Fri, 02/13/2009 - 06:45

Just to muddy the waters some more we are thinking of using 1250's to increase the RF footprint and throughput.

This will be mainly on 802.11g network is the Cisco hype true, do they increase those qualities or should we just stick with 1242's and lastly would we get away with less 1250's than 1242's due to a larger coverage area.


terminalvelocity777 Fri, 02/13/2009 - 06:47

Cancel the 'how many' would we use question in comparison to 1242's as Cisco doctrine is replace 1:1 apart from in a full 802.11n environment answers to the other queries gratefully accepted.

Scott Fella Fri, 02/13/2009 - 06:58

Per Cisco and and I agree to this is it is a one to one replacement. So I you had a 1242 deplyment, you can use the same locations if you were to replace the 1242 with 1252's. The issue would be how much interference you will have due to overlapping channels. Aggressive load balancing can be enabled on a wlc and from another post, ap's that have 12 users will try not to respond to beacons from the 13th device. If the client doesn't associate with another ap, that ap will allow that 13th device.

ericgarnel Fri, 02/13/2009 - 07:00

I deal with this issue on a daily basis.

We have seen as many as 1755 simultaneous users on our wireless and expect to go over 2000+ simultaneous users in early March.

We use the 1252s in a high density deployment.

For dense crowds, such as large breakouts, key note speeches, etc. we deploy "field kits" that consist of either 1252 or 1242 APs, some of which are mounted on tripods or placed below chairs. We also will use directional antennae to help steer the signal.

People aka "bodies of water" absorb rf which we use to our advantage to pack in more APs in a given area. We also adjust the user counts per AP as well as "steer" 802.11a/b/g clients towards the 802.11a side by tweaking the 802.11.. signal properties.

Be careful of how you handle throughput, you do not want to have a great wifi signal, but clog your internet pipe.

A survey is great, but when you pack a room full of people, chairs, truss, etc, the dynamics change drastically.

Leo Laohoo Sun, 02/15/2009 - 15:57

Alot of good points above. Before you make a 1:1 replacement, make sure you have a Wirelss Site Survey using the AP or your choice.

The 1250 has a new "little brother" which can also do Draft N 2.0, the 1140. Unlike the 1250, the 1140 can operate using standard PoE but the range of the radios have been curtailed. The 1250 "can" work on standard PoE (either removing one of the radio modules or cranking down the power). To get the 1250 to operate at full power (radio transmission and range), you either put a power injector or use a switch that will support Enhanced PoE (3560-E/3750-E, Sup720).

The difference between the two is the suitability of a location. The 1140 is designed for office environment (cubicles, offices, compactors, etc.) while the 1250 is designed for warehouse environment (large open space).

Here are some options you may want to consider:

Cisco Aironet 2.4 GHz and 5 GHz Antennas and Accessories

Cisco Aironet Antennas and Accessories Reference Guide

ericgarnel Tue, 02/17/2009 - 06:23

Another issue to consider is the wired infrastructure that supports the wireless.

We are pushing 3560-E series switches out not only to support the power requirements, but also to provide sufficient backplane and bandwidth to support and scale for the 1252 APs.

Here is a great article in the cisco ip journal that outlines some the needs for the newer wireless

ericgarnel Wed, 03/04/2009 - 12:51


the shorter stands are sign easels that have been left over from various shows. The tall pole is a leftover work-light pole that we cut the light off of. The pole is handy as it can extend to 11 feet. You can get the poles at many hardware stores.

I also use mic stands as well, they work great with 1252s

Things that come in handy:

PVC (outdoor conduit cuts & drills easily)

zip ties: cannot ever have enough zip ties

velcro: fabric of the eighties

miscellaneous bolts, screws. most of which came with various network devices.

switch or router rack mounts- very handy

hose clamps - awesome for mounting to rails!

Moly bolts

a bad a$$ drill with lots of bits.

I will also use sand bags, cinder blocks, etc to lock APs to using cable locks for under chair deployments.

The field kits are used for high-density breakouts & sessions where ceiling or wall mounted APs cannot provide adequate coverage.

terminalvelocity777 Thu, 03/12/2009 - 10:44

I agree, great information and tips from guys who are in the know many thanks to eric and others who responded.


terminalvelocity777 Thu, 03/12/2009 - 11:31

Following on from my initial question, the venue we are covering holds 5000 people. In a broad sense how many AP's would be required to cover for amount of users (what is the ball park figure for how many users can be on an AP with good performance) I realise this is a vague question but any answers would be appreciated.

Leo Laohoo Thu, 03/12/2009 - 17:28

By default, 12 clients associate to one AP and the maximum is 75.

I doubt if you can find 5000 people simultaneously using your WLAN.

You can install between 300-500 AP's.

During the intial setup phase, I would recommend that you constantly monitor your client numbers. Install 300 and if it reaches the saturation point, then put extra AP.s If not, you can always pull down the AP's.

Hope this helps.

ericgarnel Sat, 03/14/2009 - 17:05

We just hit 5278 simultaneous users at SXSW.

I used only 135 radios strategically placed.

Mostly 1252s with a handful of 1242s and about 4 1020s for nooks & crannies.

The field kits worked like a champ! For the high density key note, we deployed radios under chairs and secured them to sandbags with cable locks.

Radio count depends upon your environment and other factors.

There were lots of iphone users that really hammered our dhcp servers! We starting seeing buffer errors on the gig nics. Switched one of the servers from linux to freeBSD and it handled the load much better.

Leo Laohoo Sun, 03/15/2009 - 15:42

"I doubt if you can find 5000 people simultaneously using your WLAN." < --- I take my words back and will eat a humble pie. :P

What did you set your Client Threshold to (default is 12) Eric?

ericgarnel Mon, 03/16/2009 - 07:26

5592 was the magic number yesterday!

Today will be the last chance to beat it, before the interactive part of the event winds up.

I am assuming you are referring to the profile threshold for traps, if so, that # is 75.

terminalvelocity777 Mon, 03/16/2009 - 10:13

Hi Eric,

It was a general question about how many clients can actually associate as a rule of thumb. Depending on where you look it says anything from 2048 (eek) to 10, i know it depends on the apps etc etc.

But I just wanted a guideline answer if one exists of what an average amount of clients to an AP is in a good working system.



Leo Laohoo Mon, 03/16/2009 - 15:36


By default, the WLC is configured to 12 but Cisco says 25 is OK. You can configure this to hit the maximum number of 75.

ericgarnel Tue, 03/24/2009 - 06:08

Nope, the event is over. We will wait until next year to try and break the record. A few observations...

In the ultra high-density areas where there are many rows of chairs, you will need to place APs under and around the seats. We used 1242 radios this year because that is what we had on hand. Next year, we hope to use a radio with integrated antennae. I would make my rounds though the building during the day just to correct antenna polarity on all the low APs with "rubber ducks". People feel compelled to play with the antennae for some reason.

We also saw an interesting issue with our isc-dhcp servers running on CentOS with the default buffers for /proc/net/ipv4:

the buffers would fill up and the servers would not be able to dish out dhcp requests fast enough! I would do a tail -f on /var/log/messages and watch the file scroll by rapidly. It looked the "Matrix" screensaver! I bumped up the buffers on the servers, moved some of the other services like dns to other boxes and brought up another dhcp server running freeBSD which seems to handle the load better. I am more comfortable with Linux, but freeBSD is similar enough to Linux that I can work with it.

Also, the lowest height setting in WCS floor area ap positioning is 3ft (@1m). I am going to ask if Cisco can change it to 1 ft.

Leo Laohoo Tue, 03/24/2009 - 14:26

Thanks Eric.

"People feel compelled to play with the antennae for some reason." < --- What they do during their spare time is non of my business!



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