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We are currently talking to vendors of wireless solutions for a wireless deployment in a university campus with some 5000 students.

One vendor is offering us a Cisco solution with a WLC 5508 controller and 69 2x2 MIMO Dual-band/Dual radio APs (Aironet AP 1042 model)

The other vendor is offering us an Aruba solution with a 3600 controller and 96 2x2 MIMO dual band BUT single radio APs (Aruba AP93)

Both vendors are charging 82.000 US$ (support, 3y service contracts, switches and additional required options all included of course)

The Aruba vendor is trying to convince me that 96 single radio APs will give us more connection/users/capacity then the 69 dual radio APs.

I have my doubts about that and since it is my core competence-domain I wanted to ask here the opinion of people that have a more profound knowledge and experience in this area.

When you talk to vendors it's often hard to get objective information. So try to answer only if you are sure and please mention it if you are affiliated with one of the vendors.

I appreciate all useful help and want to thank you in advance for the effort!

John Gardeniers
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gert_78
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    I'll throw out a plug for Ruckus Wireless. I have no affiliation with them but I'm using their gear in a couple sites (one w/ roughly 60 APs spread over 5 primary school campuses) and the gear has performed beautifully. I can't give them enough kudos for the nice things their gear does. Their "beamforming" APs give absolutely _awesome_ coverage, too. – Evan Anderson Nov 15 '12 at 21:02
  • Thank you John, I'll take a look into it. But the project I'm working on is a university in Peru. So I would have to check if they are active there. – gert_78 Nov 16 '12 at 16:05
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    That doesn't seem like near enough of either. The campus I work at has 70 single-radio APs with a student body of <500, and we're still looking to add more. – Joel Coel Dec 11 '12 at 20:06
  • Do note that aruba AP 105 is dual radio. – PeterTheTech Jun 05 '13 at 07:12

4 Answers4

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The Right Answer(tm) is that It Depends(tm).

Generally, dual radio APs have higher client capacities than single radio APs, but roughly the same coverage area. Conversely, however, single radio APs can be distributed in a wider area, allowing each AP to use a lower transmit power and spread the client load across multiple APs. It's a tradeoff. More clients in a tigher space generally means that you need more radios.

If you're going to have areas of high client concentration you will typically need fewer dual-radio APs in those areas than you'd need single-radio APs.

Whether your clients are 802.11b/g/a/n makes a different, too, because a network with predominantly 5.4Ghz clients will be able to pack more densely with fewer APs simply because there are more non-overlapping channels and the APs don't have to function as "spotlights".

Evan Anderson
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  • Hi Evan, thank you for answering. But I don't quite understand it. For example what do you mean by "however, single radio APs can be distributed in a wider area". Would you be prepared to have a skype chat or so to give me some further explaination? – gert_78 Nov 16 '12 at 16:10
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    @gert_78 - I don't have any time today at all, unfortunately. I'm just too booked-up. What I was trying to say, briefly, is that 96 APs can be spread out, physically, further than 69 APs simply because there are more devices. – Evan Anderson Nov 16 '12 at 16:27
  • Evan, I would be interested in getting some more details about you experiences with Ruckus because we are considering that solution now. Can I get in touch with you in one or another way? – gert_78 Nov 27 '12 at 09:42
  • @gert_78: Drop me an email at my corporate email address (look at my profile) and we can discuss. – Evan Anderson Nov 27 '12 at 15:50
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Disclaimer: I have a significant amount of experience with Cisco 802.11 APs and WLC 5508s and no Aruba experience except for sales demos.

If both solutions meet your needs regarding coverage and client associations, then "performance" isn't really an issue as it relates to throughput. Personally, I'd go with the dual-radio APs for the obvious advantage of increased performance for newer clients.

I'm not sure what "connection" performance Aruba is referring to, but I'll assume they're talking about total aggregate throughput. When you're talking 69 vs 96 APs in a dense environment, you're probably talking a couple of hundred active users at a time, minimum. Just for round numbers, let's assume you average 1,000 wireless users (or roughly 15 people per AP). Each of these APs are 1GbE back to the controller, but your connection out to the internet will probably be much less than that.

If your connection to the Internet is 500Mbps and you have 1000 concurrent wifi users, their average available bandwidth is about .5Mbps.

The point is that unless you have an extraordinarily fast pipe to the Internet, "performance" doesn't matter as much as coverage and the ability to dynamically adapt to interference and if this is a dense deployment, I'd want both dual-band and Cisco Clean Air.

MDMarra
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    Just to follow up a bit, the LAP1042 APs don't do Clean Air. You should see if you can get them to throw in APs that have that for the same price. If not, I deployed well over 200 1042s at the university that I used to work for and they were very solid. Also, strongly consider getting two WLCs and configuring failover. It saved me more than once. – MDMarra Nov 15 '12 at 21:09
  • Thanks for answer. True, the AP1042s are not able to use the clean air technology. I also understood that it more geared toward dense environments like hospitals. This is a uni campus and is not really dense. – gert_78 Nov 16 '12 at 16:13
  • @gert_78 Trust me, there's plenty of interference at a university. PS3 controllers, microwaves, cordless phones, etc - all ruin 2.4GHz RF. Clean Air is a useful (though certainly not mandatory) is a university environment. – MDMarra Nov 16 '12 at 16:14
  • What the Aruba guy literally said was: === "We conducted an analysis of the product (I assume he means the Cisco APs) and AP93, while Single Radio, has more power in dB so its performance is similar to Cisco 1040 with Dual Radio. By having a greater number of Access Points, the coverage will be higher and better. Aruba solutions, allow also manage connections of users. The user's device will always try to connect to the Access Point with the best performance according to defined policies" === I'll ask for clarification from his side. – gert_78 Nov 16 '12 at 16:18
  • Yeah, I'm not sure how `The user's device will always try to connect to the Access Point with the best performance according to defined policies` can be true, unless they're doing things like dropping probes, since which AP devices associate with is really a client-side thing. That said, Cisco APs also support this, by doing exactly that, dropping beacon probes from clients on all but the preferred AP in a given coverage area. Really though, if both solutions meet the coverage and capacity requirements, they'll probably end up performing largely the same. – MDMarra Nov 16 '12 at 16:22
  • @gert_78 what do you mean "not dense"? Between residence halls and lecture halls, university networks are about as dense as they come. A lecture hall can easily put 100+ wireless users into a fairly small room. – Joel Coel Dec 11 '12 at 20:10
  • @JoelCoel Tell me about it. I had lecture halls with two Cisco LAP1142s in them, simply because of the maximum capacity of the room :( – MDMarra Dec 11 '12 at 20:18
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    @gert_78 The Aruba product might be just fine, but that sales guy has no clue. Higher dB is very often worse for a wide deployment, rather than better. – Joel Coel Dec 11 '12 at 20:34
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Neither bid sounds anywhere close to adequate.

A rule of thumb I've used is that one AP radio will support up to about 25 clients for normal traffic. If you want to support high-bandwidth applications such as streaming video, that number only drops. Dual vs Single radios don't matter much to me: it's just that if you have single radio APs you're placing more APs in the same size space, which means more switching and power infrastructure... but they also mean the APs will overlap, so if one goes down from loss of power there is likely still some service in the area.

The big thing is that even the dual-radio APs need those radios use the proper channels. With only three non-overlapping channels in the US, and only about 25 clients per radio/channel in a given space, supporting more than 75 devices in a single area — such as a lecture hall with more than 75 seats — is a real challenge.

Now the good news is that not all of your 5000 students will be online at the same time, but even assuming only 1000 concurrent users, with 25 users per radio you are looking at a 40 radios as a starting point. Remember: this is just the starting point. There are lots of factors that mean you will need more than this. Let's look at a few of these:

If you are a residential campus, you need to double this number, as it means your student body is almost entirely in one area of campus during the day (classrooms, activity areas, administrative areas, etc), and almost entirely in another area of campus (residence halls) late evenings and early mornings. Also, this assumes a perfect distribution of users across these areas of campus. That might be true in residence halls, where students have an assigned spacing in rooms that is fairly consistent, but you'll find you need to about double your initial radio count again for the more public areas of campus as students spread out and move around in groups from place to place. The residence halls have their own problems, as the concurrent user count can approach your actual student FTE at certain times of day in the halls... in other words, add that radio count again. This brings us up to 160 radios so far.

Finally, you need to look at your really dense spaces. Here, I'm talking about lecture halls, common spaces where students like to bring laptops, and stadium areas if you want to provide wifi there. These spaces will all need additional radios. You also need to look at your really sparse spaces, like parking lots and green spaces. You may not want to provide wifi to parking lots, but I'm betting there are some nice public outdoor spaces where students would like to be able to sit on the grass with a laptop. Count some radios for here, as well.

If you have older building with brick or block construction, this can add significantly to your required radio count as well, as wireless signal will lose a lot of strength passing through that material.

I know these are all back-of-the-napkin kind of numbers, but I'll be very surprised if your deployment doesn't end up at least twice or even three times what you're looking at, right down to a second load-balanced or fail-over controller.

Joel Coel
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Maybe u can give Aerohive a shot. Heard they give controller less solutions, meaning infinite scalability. Its cloud based or locally VM hosted management (Not controller)

The reason i'm mentioning this, is because this is the third time i'm hearing aruba pitching 93 againt better radioed APs. I've stopped trusting their reps basically now,

Frank Sinatra
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    In practice, instead of infinite scalability, controller-less means hand-managing numerous access points. This **can** work (we do it where I'm at), but know what you're getting into. – Joel Coel Dec 11 '12 at 20:32