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Best WAP For Dense Crowds?
An anonymous reader writes "A local community organization has asked me to help them set up Wi-Fi access for an upcoming event, with some unusual (to me) requirements. All users (up to 500 people) will occupy a relatively small area and more-or-less have line-of-sight to the WAP, so issues like signal strength and wall penetration don't matter. Security also does not matter, as we plan to open this to anyone wanting to connect. Cost always matters, but we realize a $50 Linksys or three won't cut it here.
In the past, I have used Cisco AP1200s for a few dozen users to great satisfaction, but they only handle 50 connections at a time, and practically count as antiques at this point anyway. My research on the matter tells me that 802.11n performs far better in this regard, but I want to support 802.11g as well. I have no objection to using two APs to split those apart (with n limited to 5.8GHz, as per the suggestion of several comments in a recent Ask Slashdot), but physical constraints make it preferable to minimize the total number of APs needed — Ten WRT54s might cost about the same as one Aironet, but I only have three good places to mount these.
I welcome any suggestions and real-world experiences with similar situations, including the ever-popular Ask Slashdot refrain of 'What kind of idiot would do it like that, when you can just do this?' Ideally, I would like to know model numbers and how well they held up under real-world loads comparable to my situation."
there was a slashdot the other day about the wifi at a python conference.
any AP is only going to handle 50 users or so because 802.11x is contention based.
So go ahead and get yourself 10 APs, spread them out, and make sure the ones near eachother are on different channels.
Xirrus 'Arrays' are designed for what you're doing. I've used 2 4-radio Xirrus arrays to serve 240 users in a single ballroom. http://store.xirrus.com/SearchResults.asp?Cat=4
I did a little googling because I was worried about the number of clients. 802.11 uses CSMA which means that every client must wait for every other client to go silent before transmitting.
That means that you would have to take the minimum latency and multiply it by 500 since all clients will be equals. That puts you into 500ms of theoretical latency per packet.
What this means practically is that with 500 clients using all roughly the same bandwidth at 54Mb (unrealistic BTW) you would have just 110Kb per second available to each with 500ms+ latencies, which will compound exponentially.
Though on paper you might be able to show that ability to connect this many clients but realistically, on HIGH end hardware your are going to have a 50 client MAX simply because of CSMA requiring everyone to take turns but less any bandwidth sharing.
To make things worse, the amount of data having to be moved just to keep everyone connected and to communicate who is 1st,2nd,3rd, etc in line to speak is going to cut your bandwidth to a tiny fraction of the link speed.
I highly suggest that you take one of the early poster's advice and drag some cat5e around. You might have some lucky with 'CELLS' of WRT54g type routers with a carefully selected channel scheme where a set of 4 routers would have channels 1,4,7,10 and the next closest 2,5,8,11 and the next 3,6,9 and then start over. The channels will overlap somewhat but having 11 SSIDs for 500 people even with some channel interference would get you to somewhere around 50.
you could extend that to put some 5Ghz band routers in each router bunch and hope that people are fairly evenly split between G and 5Ghz N
Background on me to qualify my comments: I am a cisco engineer specialising in wireless and security. My product recommendations later come from this experience but there are other products capable of the same performance such as the aruba equipment which would be my close second recommendation but i have no specific product knowledge.
I think you need to refine your requirements. It is highly unlikey that a crowd of 500 people will create 500 connections. You will probably end up serving 100-150 clients simultaneously but not all of them requesting data at the same time unless there is something specific that all users need to connect to at the same time throughout the event.
Without much better information everyone is just throwing out a product, not a design. And as you clearly are not a wireless expert (as you asked for 802.11n "as well as .11g) i would recommend finding someone who is to consult properly.
And for those suggesting consumer products, your dreaming. Without some form of spectrum management in this situation the asker is doomed to provide a very poor service with no roaming and massive 2.4ghz congestion. In addition, those people recommending wired access, WTF? You very clearly do not understand what you are talking about. Are you expecting 500 desks with RJ45 ports, or multiple 48 switches places around the room for people to huddle around with their laptops (and only laptops as no mobile device even has an RJ45 port). This is clearly a fallacious argument.
Answer the following questions and we can all get very specific.
3 points to place APs. Is this to physically mount or a cabling limitation? Can you mount more but have no cabling? Un-manged switches can help with this for less than $50 each. If only to mount then you are stuffed, There is nothing out there that will handle 500 clients with any useful service. It's not a limitation of the products it's the contention of the medium as mentioned earlier.
What services are they accessing? Are they local or is it just the internet? If the internet, what is the upstream bandwidth available? If local access at high speed (100Mb/s +) then you will end up with contention issues. If it is the internet and the pipe isn't fat you are not looking at contention issues you are looking at number of users connected. Most modern APs do not have practical limits of associated clients but most recommend around 25 per AP.
What is the nature of the event? Basically, are you providing a service that is required constantly throughout the event leading to 100% of attendees connecting all the time. Also, are users accessing a high bandwidth service (streaming video for example) all the time or things like static web pages delivered via http? The later will deliver small amounts of data to each person but will then take time to read by the attendees al will also be cached locally meaning subsequent connections will require even less bandwidth. If streaming video, someone should have though of this earlier and you will need a consultant/engineer 100% or expect to fail.
An off the cuff answer without the above knowledge assuming http type data required, cabling limitation not mounting, the more realistic 150 simultaneous users and internet link at less than 30Mb/s:
1x Cisco 2112 Controller (100Mb ports not important as limited upstream)
5-9x Cisco 1142 APs (very nice 802.11n dual band with the ability to force people to move to 5Ghz if they have it 6.0+ code)
3x gigabit unmanaged switches (something like dlink DGS-1005D)
It would not be far fetched to contact decent size Cisco/Aruba/VendorX partner and get loan equipment for a price + a consultant as part of the deal.