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Wi-Fi Isn't Magic



Wi-Fi may seem like magic when you’re streaming your videos and reading your email. But it has to obey the Laws of Physics. This video will describe some of the things you’ll need to consider if you want to get the most out of Wi-Fi. 

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Transcript for Connectivity College: Wi-Fi Isn't Magic Video

Hi! I'm Paul Frisbie. I'm here to talk you about using wifi inindustrial applications.
 
Wifi may seem like magic when you're streaming video in an airport lounge or reading your email out on the patio. But, wifi depends upon technology that's more than a century old. Modulated electromagnetic waves to radio. The frequencies may differ, but wifi is pretty much the same thing that opens your garage door, heats up your soup in the microwave oven and lets your key fob unlock the car. It's just radio and it's still subject to the same limitations which existed back in Marconi's day. Wifi has to obey the laws of physics. It's not magic, far from it. 
 
Now this, is magic. Choose one of these cards, any card is fine. Memorize it. Now let's wait a few seconds while the amazing Professor Frisbie reads your mind. Ahh.. it's coming to me. It's not this one or this one, or this one. So where did your card go? 
 
If nothing interferes, a radio signal will continue with the square of the distance. But different frequencies behave differently in different environments. The higher the frequency the more easily radio waves are absorbed and reflected by ordinary materials, like the wall of the building or vegetation. 
 
Visible light, though a little higher up the electromagnetic spectrum than radio, demonstrates the principal kind of nicely. A piece of Kleenex, for example, will let light through very easily. It's not very thick, the light makes it through. On the other hand, a piece of plywood will not. 
 
Radio waves have better penetration than visible light but the principle is the same. They get absorbed and reflected. Houdini wouldn't have bothered trying to listen to the Cubs game while executing one of his famous escapes from inside the thick walls of a metal bank vault. Houdini always got out but radio waves would have had some real trouble getting in. 
 
Higher frequencies are more easily reflected so they produce more multi-path propagation, a phenomenon that occurs when transmitted signals bounce off intervening objects and different parts of the signal arrive at the receiver at different times and out of sequence. 
 
Lower frequencies have better penetration, but they also provide less bandwidth. An extreme example would be the extremely low frequency ELF communication systems developed by the US and Russian Navies. They can communicate with submarines out at sea under several hundred feet of water but they can only transfer data to read a few characters per minute. Because a broadcasting antenna must be at least a fraction of the radio's wavelength a submarine can't use the ELF system to answer back. The ELF antennas are 60 kilometers long and they won't fit in the submarine. So the primary use of ELF is to ask the subs to rise to a more shallow depth and use some other means of communication, like carrier pigeons or smoke signals, anything but ELF. Not exactly magic.
 
So, because wifi isn't magic and has to obey the laws of physics, you'll want to use the 802.11n standard for industrial wifi applications. 802.11n addresses radio's weaknesses. It uses multiple input/multiple output antennas, multiple spatial streams, a channel length of 40Mhz, spatial uniforming, frame aggregation and other useful tricks. 
 
The 802.11 standard works within the laws of radio rather than try to fight against them. Some industrial wifi devices can broadcast in both the license free 2.4GHz range and the license free 5GHz range. That's a useful feature. 
 
Radio behaves differently depending upon the immediate environment and no two locations are exactly alike. Depending upon your situation, you may find that either the higher or the lower frequency produces the more desirable result. There's a lot of different wifi equipment on the market so pay close attention to specs. You want a device for the high-end processors so they can support enterprise-level security. Low-end devices won't do that. 
 
As always,if you have any questions about industrial wifi or industrial networking in general, feel free to contact our technical support. It's always free and our application specialists are always happy to help. And in a world full of automated voice menus that lead you around in circles, finding real human beings who actually answer the phone can seem a bit like magic.
 
Thanks for watching.