Best way to handle high usage in a small area

We've been asked to provide wireless laptop access for a group of people attending a conference. All users will be in one conference room approx

30ft x 50ft. Estimate 50 wireless users. They will be doing medical imaging type application over the web (i.e. needing lots of bandwidth). We're thinking of putting 3 Linksys WAP54G's or WRT54G's in the room roughly in a triangular pattern.

Should we put each one on a different channel (1, 6, and 11) ?

If they all have the same SSID's, what would be the odds of relatively even user distribution across the APs in a room that small?

Perhaps we should use 2 APs with 2 different SSID's and tell people on one side of the room to connect to network A and the other side to connect to network B?

TIA,

-- Paul

Reply to
Paul
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How big is your internet pipe? It has to be pretty big to not be the bottleneck vs the WI-FI links.

Mike Schumann

Reply to
Mike Schumann

In a perfect world, we would have access to the conference center's full

45Mbps connectivity. The reality, maybe 10Mbps, worst case 3Mbps. Those details are somewhat elusive because we have to work with the conference center's ISP which is a bit difficult to get straight answers. For the sake of argument, let's say bandwidth is not an issue...

-- Paul

Reply to
Paul

Argh. 50 full time users is going to require at least 3 access points. Try to stagger your demos and downloads or you're going to kill the backhaul. Better yet, get some kind of web cache device and buffer the traffic locally. If the web content can be downloaded, save it on a local web server and have the users grab it from there instead of from the internet.

I once did a system like this for a seminar at a local hotel. Only 30 attendees but still a big mess. Just about everything went wrong. The hotel was using a mix of 802.11b and 802.11g access points. Everything on one SSID. The backhaul was a 1500/256Kbit/sec DSL line. As soon as everyone turned on their laptops, most of them decided that this was the perfect time to update their virus scanner, run Windoze update, automatically check for email, and synchronize their calendars. The DSL was totally staturated for at least 30 minutes until the traffic settled. There may have been a virus or worm running among the attendees, but it probably gave up when faced with the constipated DSL pipe.

The mix of access points lacked "client isolation" or "ap isolation" features. This is to prevent clients from connecting to each other or attacking each other with worms. Some had it, some didn't. That resulted in users creating a few ad-hoc networks, which generated LOTS of interference as they passed home movies between attendees instead of paying attention to the speakers.

With all the same SSID traffic was not exactly balanced. The users with 802.11b radios really slowed down the 802.11g access points, but they couldn't turn off 802.11b compatibility because there were some users with 802.11b only hardware.

During the seminar, one of the speakers passed out a cdrom that included online registration in order to activate the demo software. Everyone plugged in about the same time causing the router to detect

30 connections to the same IP address. The hotel IDS declared this to be spam or an attack (I forgot which) and blocked furthur connections to this IP. Most of the registrations failed for about 30 minutes until someone disarmed the IDS.

Part of the demo included streaming media from the internet. 30 laptops all went to the same web pile, from the same routeable IP, and caused the site dispensing the streaming media to declare that it was being somehow attacked. It turned off for about 10 minutes causing substantial head scratching.

The worst problem was that several idiots (including me) decided to "do something" about the traffic problem. Much of our tweaking with QoS and blocking sites did more damage than good. Repeated access point reboots along with corresponding client disconnects, were not very popular. We would have been better off leaving everything alone than trying to twiddle and tweak blindly.

Are you sure you want to do this?

Yes. 3 access points, 3 channels.

In the past, I've always suggested using the same SSID so that it's easier for users to roam. I changed my mind. The typical wireless client is stupid. There's no algorithm for selecting the strongest or best access point. Most will pick the first one it hears and stick with it almost forever. The signal could turn to garbage but the client will not go searching for a better access point until it literally disconnects. This is not true for all clients. Intel Proset is rather smart about roaming for the best access point. However, this is the exception, not the rule. However, even with Intel Proset, you're still not going to get an even distribution of users per AP. If one of your AP's is a bit stronger or more aggressive than the others, it could easily get ALL the users to connect to it. Seperate SSID's may take a bit of explaining, but at least you won't have as much crowding.

Three AP's with 3 SSID's on 3 different channels (1, 6, and 11).

Good luck and try not to repeat my mistakes.

Reply to
Jeff Liebermann

Given 3 APs, put them on 1, 6 and 11. I would use the same SSID due to the hassle factor.

Aaron

Reply to
Aaron Leonard

Maybe the answers so far are for the wrong Q.

is there some easy way to provide Ethernet ports to some of the users, so you can cut down the number of wireless clients?

in a lot of cases where you have laptops needed for longer access they end up tethered to a power cable anyway - so you probably have organised power feeds to part of the room? Otherwise things start to degrade as all the laptop batteries go flat......

most of the big conference tables at work have a UTP + power feed (or several for big tables) - so a connection or 2 and a multiport switch will give users willing to be "tethered" a faster more reliable link - and free up wireless capacity for those that want / have to use it.

Reply to
stephen

Yes, as a backup I am planning on hardwiring the tables in the conference room with Cat5 drops every couple of feet so people can just plug in if necessary.

-- Paul

Reply to
Paul

Ha, well, it's not my choice. The customer is always right ya know...

Thanks for the input !

-- Paul

Reply to
Paul

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