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New Member

Advice: Number of AP required for large number of users

I am task to take over a wireless project for a convention.

Scope: To provide wireless coverage for a convention room of about 120m x 100m with some rooms partition for private meeting(sound proof). Need to cater for about 300 concurrent users.

An initial design proposed about 30 AP (1242) with an 4404 wireless controllers.

I feel that the number of AP is excessive for this coverage.

However, he mentioned that there is a rule that 1 AP should serve only about 20 users.(I cant find any reference to this in Cisco)

My questions:

1) For high number of expected concurrent users, does using more AP help and is there really a rule stating 20 users to be the max for one AP

2) By deploying large numbers of AP in close proximity, and using the wireless controller to auto regulate their frequencies and power, will we still run into problem with signal quality, strength and crossovers.

Please advise

12 REPLIES
Super Bronze

Re: Advice: Number of AP required for large number of users

Hi

It really depends on how much traffic your users put out... It may seem excessive but it's better to have more bandwidth than less especially if people are dependant on the wireless.

The nice thing about LWAPP is you could reduce the number of APs initially, and add more later if needed (provided you have a controller with spare capacity) without worrying about re-arranging 802.11 channels and power levels...

1200 series seems an odd choice - the 1000 series would give you a simpler deployment as you don't have to convert them to LWAPP capable IOS, just cable them in and you're done (assuming your controller is running!).

The 4400 controller will take care of signal/channel arrangement for you - in my experience this works very well.

If you have lots of APs in close proximity, there is also a 'pico cell' mode that optimises the controllers for small wireless cells.

Hope this helps

Aaron

Please rate helpful posts....

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: Advice: Number of AP required for large number of users

Hi Aaronharrison,

I have similar problem. We want to connect Aironet to ethernet backbaone in cat 6500 with 24 vlan. The AP 1200 broadcast can only reach a certain Ip address. So far no controller is used, Just AP1200, cat 2950 (access sw), cat 2950 (distribution sw) and cat 6500 (backbone sw). So is it necessary to use controller for 300 user in 6 Flr? or can I use Vlan Trunk and L3 routing?

Thanks.

PS: if this post is a bit of topic, please reply to bsutanto@istrainternusa.com or istra1@tekom.net

New Member

Re: Advice: Number of AP required for large number of users

The 4404 Wireless LAN Controller is marketed as the perfect solution for something like this, but we have not had the success that we were expecting. We have found that in an environment where there are a lot of access points you still run into issues with channel contention even though the AP is supposed to adjust itself. The APs dont seem to step down as they should. We end up manualyl adjusting the settings making the controller an expensive management interface. Hopefully other people have had better success.

Super Bronze

Re: Advice: Number of AP required for large number of users

Hi Tod

We've had one customer (out of many) who had a similar problem a couple of weeks back... Basically had terrible signal everywhere, and suspected the APs were putting out too much power.

Fortunately he had dual WLCs, so we pulled the plug on one, and it all came back to life.

Switching to the other controller returned the system to poor service.

I went to site, upgraded the controller firmware and rebuilt the config (as we couldn't imagine it being a hardware fault) and we're waiting for the customer to pick a good time to test it out...

So your problems may be the result of a bug or something? We had another bug where Intel 2200BG chipsets wouldn't work with G mode, TAC denied it was a problem right until the last firmware was released and it was in the release notes!.. so who knows..

Aaron

Aaron Please remember to rate helpful posts to identify useful responses, and mark 'Answered' if appropriate!
New Member

Re: Advice: Number of AP required for large number of users

I apologize for getting this post off topic. This customer I am working with right now has only one WLC. We have upgraded it to 3.2.150-6 and it did not improve the issues. Most APs are operating at their maximum power even thought 6 of them can see each other clearly. We have tried just about every setting and the signal is awful because of all the contention. Currently have a TAC case open and they are blaming with Linksys and Intel Wireless cards. I have even considered disabling 3 of the 6 APs in hope of improving performance even though this will put about 25 people per AP.

Hall of Fame Super Silver

Re: Advice: Number of AP required for large number of users

Is the Group Mode in the RF Group enabled? If it is then maybe you should try disabling 3 of the access points and see if users are having performance issues.

-Scott
*** Please rate helpful posts ***
New Member

Re: Advice: Number of AP required for large number of users

RF group is enabled. I read the help, but I am not entirely sure what this does. It appears when group mode is enabled it elects an AP to control parameters of its group. I may try disabling some access points tomorrow. I also disabled aggressive load balancing (controller settings) and short preambles (global RF b/g) a while ago trying to get less disconnects from users. Neither appeared to help. The problem with this install is most users work with databases and when their wireless drops they lose their session and their data.

Hall of Fame Super Silver

Re: Advice: Number of AP required for large number of users

One other thing you might want to check is the switch logs t see if the interface is bouncing and if you are using a RADIUS server, check the logs. We had issues with users dropping every 8 to 15 minutes and it was due to switch port configuration. I don't know what else you can do except for trying to disable the other AP's.

Make sure the users are not jumping from the SSID you have configured to a ROUGE access point either.

-Scott
*** Please rate helpful posts ***
New Member

Re: Advice: Number of AP required for large number of users

Thanks for your suggestions.

Disabling 3 of 6 radios did not help. We are still testing with 4 of 6.

Both controller and switch are configured for 1000 Mbps Full Duplex. I did notice a ton of Undersize packet errors on the switchport that is connected to the first controller port. This is where the majority of wireless traffic goes.

There is a lot of wireless activity around this building. It is mostly glass and the controller picks up at least 7 rouque access points.

Hall of Fame Super Silver

Re: Advice: Number of AP required for large number of users

So you hard set both the controller and the switch port to 1000 full?

Set the primary controller of all the ap's to one and use the other as a backup. See if that helps. Also are you sure that users are not hopping on one of those ROUGE ap's?

-Scott
*** Please rate helpful posts ***
New Member

Re: Advice: Number of AP required for large number of users

Yes. Both switch and 4400 are hard coded to 1000 full. Cisco wants me to set both to auto/auto, but that goes against all I have learned over the years with connecting cisco devices.

I have all WLANs and APs set to use port 1 and it does not seem to help.

It is strange. I dont see any errors or collisions on the ports but I do see a ton of undersize packets. It makes me wonder what the undersize traffic is. Could it be malformed packets that are coming from the APs that are the cause of the issues?

New Member

Re: Advice: Number of AP required for large number of users

Hey gang, we are in the same boat. A Cisco recommended survey team did our site, we installed and configured as instructed and also on the latest versions of WiSM software. We have drops from all flavors of wireless clients: cisco, linksys, d-link, 3-com, intel. Just as stated in this thread, b/g network interference is at rediculous levels using auto-rf, and far too often to we see the radios at the strongest power settings. We also see interference profiles fail through the WCS. If anyone gets any more information please continue to post. We are considering disabling globally 1,2,5Mbs data rate ranges to shrink some cell sizes or perhaps lowering the beacon intervals.

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