Ever gone into a store and looked up? You’d be surprised what you can find hanging off the ceilings.
Like where I’m hanging out now—one of those tiny mobile phone stores. It’s not a large space but there are three Wi-Fi APs hanging off the ceiling in a retail space of about 400 sq. ft. (37 m2). That’s roughly equal to one AP for every 133 sq. ft. (12 m2). Does such a small place really need three APs?
Is Three a Crowd?
People who study crowd density have rules of thumb to estimate the number of people that can occupy a given space. A loose crowd, where everyone is about an arm’s length from their neighbor, requires roughly 10 square feet (1 square meter) per person.
At that density, you could pack forty people in this store. It would be uncomfortable and leave no room for shelves, tables, or check-out counters. Anyone who has shopped around a major holiday knows what it’s like to look inside a jam-packed retail store and say “Hard pass”.
Back to those APs blinking above me. Let’s assume everyone here has a Wi-Fi-enabled smartphone. At our maximum crowd capacity, that’s 40 devices, plus a few more if the store uses Wi-Fi for point-of-sale (POS) devices. Let’s round up to 60.
You might think to yourself, “60 devices divided by three APs is only 20 devices per AP. That’s great!” Except most APs have dual radios. The actual number will be 10 devices per radio.
I can hear you now. You’re probably the person behind me in the check-out line wondering why this woman is muttering to herself about APs. “Isn’t fewer devices per radio better?” you’d say.
First, is everyone really going to be using all of those devices at the same time? The answer is almost certainly no. Let’s assume 50% of these devices are actively used at any given time for email, web surfing, cat videos, writing blogs, and so on. Everyone else is shopping, paying at the register or wondering if they have time for a Starbucks run later.
That leaves us with 30 active Wi-Fi devices: 5 per AP radio, or 10 per AP.
If that’s the case, why, you might ask, would someone put not one, or two, but three APs on their ceiling? This is not a physics or math problem. The answer, I suspect, lies in an intuitive understanding everyone shares: If a little bit of something is good, more is better.
But like ketchup on French fries or water in a bathtub, there is a limit after which more makes things worse instead of better. Wi-Fi is like that. Flooding a space with more and more RF reaches a point where you’re gonna spend more time with a mop than enjoying a relaxing bath.
Here at Ruckus, we spend a lot of our hard-earned research dollars figuring out how to make Wi-Fi work even better and support more devices per AP. Not only does it give you more Wi-Fi for the dollars you spend, but it also reduces the potential for too much RF interference and the terrible troubles it would unleash on an unsuspecting IT network engineer. If you’re interested in learning more about RF interference and its impact on Wi-Fi capacity, check out this blog on the 3 myths of Wi-Fi – interference, capacity, and roaming. While you’re there, check out some other blogs written by really smart people who probably don’t stand in check-out lines staring at the ceiling and muttering to themselves.
In the meantime, keep an eye out and don’t be afraid to ask, “Is more really better?”