July 23, 2014

Teaching Science with Wi-Fi (Thanks, Ruckus and MetaGeek!)

As a parent, especially a techie one, you never know when a teachable moment is going to appear. Last night, I mentioned that I was testing a new Ruckus access point and enthused about how fast it was. My 12-year-old asked, “why is it so fast?” This led to a wonderful discussion about radio waves, congestion and propagation, and spectrum licensing. Yeah, I’m that kind of dad.

I started by explaining a little bit about radio waves generally. “There are radio signals that are very low frequency, with a long wavelength, as well as those that are very high frequency.”

“What do you mean? What are radio signals?”

“Radio signals are like waves in water,” I said. My wife, the science teacher, quickly brought up a picture of the electromagnetic spectrum as an illustration. “There are tiny, ultra-high-frequency gamma rays and x-rays, as well as light waves in the middle and lower frequency radio waves.”

“So there are radio waves all around us right now?”

“Radio signals are like light, only in a color you can’t see,” I explained. “Every radio device sends it signals out in all directions, hoping an antenna will pick them up. And the spectrum of all these frequencies is divided up into segments like television channels.”

Big mistake: My TiVo-raised kids have no idea what a television channel is. But they had some idea about radio stations and could understand that different frequencies could contain different information.

So I transitioned into a discussion of congestion. “The phone and the computer are like flashlights, but it’s hard to see a flashlight in a bright room. If the room has blue lights, and you turn on a red flashlight, it will be obvious. But a blue one would be almost invisible!”

“So why is 5 GHz Wi-Fi so much faster than our old network,” asked the kids.

“There are 2 reasons,” I answered. “First, the 2.4 GHz spectrum used by regular Wi-Fi is really crowded, with lots of devices sharing it. Even telephones, cameras, and microwave ovens use that frequency! Second, 5 GHz has a lot more space for everyone to share, so much that you can even use wider channels.”

“Why don’t they just make more space for regular 2.4 GHz Wi-Fi?”

“They can’t! There’s just too many other people using radio signals around there, and they can’t move them around. The same thing happened in 900 MHz, and it might eventually happen in 5 GHz, too,” I explained. “It’s important that someone regulate who uses what frequency or it would be chaos. Imagine if anyone could drive in any direction anywhere on the highway!”

“It would be pretty cool to be able to see radio waves,” one of the kids commented.

“You can,” I answered. “A friend of mine makes a little device you plug into the computer, and it allows you to see all the signals in the 2.4 GHz and 5 GHz bands. It’s used by Wi-Fi engineers to plan networks. My friend gave me one, if you’d like to see it!”

I grabbed my laptop and Wi-Spy DBx card, started VMware Fusion, and launched MetaGeek’s Chanalyzer application. In a few minutes, I had a screen full of signals in the 2.4 GHz range. Although we live in a quiet suburb with large lawns, there were dozens of devices sharing that paltry spectrum.

This is why we can't have nice things...

I then switched over to the 5 GHz band. After a moment, we saw our first 5 GHz signal. Then we saw some more, all clustered around channel 100. A quick option click on the Wi-Fi icon in the menu bar showed us that the Ruckus access point was indeed using channel 100. The only signal in the entire 5 GHz band was our own access point!

5 GHz is like a beautiful, open highway

After a while, we did see some others stray signals in the 5 GHz band. But Chanalyzer gave a wonderful visual demonstration of the contention in 2.4 GHz and the wide open spaces in 5 GHz.

I was even able to demonstrate the wider channels used by the Ruckus access point and my MacBook Pro. The kids walked away with a better understanding of electromagnetic waves, radio devices, and the rules that govern their use. Special thanks to Tech Field Day sponsors, Ruckus Wireless and MetaGeek for making this little demonstration possible!

Disclaimer: Ruckus Wireless and MetaGeek gave me the products mentioned in this post free of charge as part of Tech Field Day. I still may have had this conversation without them, but I wouldn’t have had such exciting visuals!

  • http://www.facebook.com/profile.php?id=744845830 Freddie Cash

    Install WiFi Analyzer onto any Android smartphone, and you get the same thing … for free!  And the kids (if they have Android phones) can even take it with them to explore wifi signals everywhere they go.  :)

    It’s really too bad that there aren’t free/inexpensive programs like WiFi Analyzer available for Windows.  There’s Kismet on Linux, but it’s nowhere near as easy/fun to use.

  • http://twitter.com/metageek MetaGeek, LLC

    Freddie – do you know about inSSIDer for Windows?
    http://www.metageek.net/products/inssider/

  • http://www.facebook.com/profile.php?id=744845830 Freddie Cash

    Nope, had not heard of that.  Looks very nice.  Will have to download that and give it a try the next time I’m mapping out signal strength in a building.

    Thanks for the link.