How Wi-Fi works (Part 1 of 3)

Everything is Wi-Fi ready these days.

  • Laptops
  • PCs
  • Smart watches
  • Smart TVs
  • Smartphones
  • Smart thermostats
  • Smart Traffic Control
  • Your socks, okay maybe not your socks.

But exactly how does Wi-Fi work?

I decided to write a three part guide to clear the confusion.  By the end of it you’ll know enough to make your spouse proud and win on Jeopardy.

I’ll have Wi-Fi for 100 Trebek

In part one, you’ll know how to answer these questions:

  1. What exactly are radio waves and frequencies?
  2. Which frequencies does Wi-Fi use and why?

Then in part two, I’ll unwrap the facts on:

  • How Wi-Fi turns radio waves into data

Finally in the last part we’ll explore:

  • The truth about Wi-Fi hotspots
  • Wi-Fi security – inside/out.

We’ve got a lot to cover – are you ready for the knowledge bombs?

Let’s go!

Show me your radio waves girl

Haha, okay I’m done being stupid.

Before we can even venture into the enigmatic world of radio waves we should start with something you already know: water waves.

When you boxed up all the love letters your ex-sent you and hurled them into that lake down the street, you saw a big splash followed by a bunch of concentric waves rippling out from the splash point.

Image credit Richard Freeman via Flickr

These waves, technically called mechanical waves, are a disturbance in the molecular structure of the water.  Hurling your big box into the water was the catalyst that sent millions of water molecules crashing into each other.  These molecular collisions transferred energy throughout the water and resulted in that mesmerizing pattern of expanding ellipses.

How beautiful.

Radio waves are different kind of wave because they don’t need a physical medium like water for passage – they have no problems traveling through almost anything – including the suffocating space of the universe. These waves are also unique because they have both an electric and magnetic field.  This is where we get the word electromagnetic.

Here’s a little review from your high school physics class:

Image credit Bob Mical via Flickr

If you take a horseshoe magnet and find a way to rotate or move a wire inside the magnetic field created by that horseshoe magnetic – guess what happens?

Any ideas?

The inert electrons hanging out in that wire get pushed.  And moving electrons is exactly what electricity is.  Conversely, by the same logic a moving electric field can also create a magnetic field.  So electricity and magnetism are like two sides of the same coin – you cannot have one without the other.

It’s like Bert and Ernie.  Bart and Milhouse.  Snookie and The Situation. (Whatever happen to that show anyway?)

Now if could find a way to oscillate between creating electricity and magnetism you would get something like a wave.  And that’s exactly what an electromagnetic wave is.  In fact, visible light and every other form of electromagnetic radiation is based off this basic principal.

Electromagnetic waves are all around you right now.  In fact, the wireless game controller on your XBox One console is emanating electromagnetic radiation through the air.  But that’s not all, you can add these common items to the list:

  • The Sun
  • Your monitor
  • Power Strip
  • Microwave
  • TV
  • Kitchen appliances

Almost every piece of technology with an off switch shoots out electromagnetic radiation.  But this isn’t necessarily a bad thing because most of the radiation is benign.

Let’s talk about frequencies for a minute.

The frequency is the number of times the wave cycles (measured in cycles per second, also called Hertz, HZ).

The distance between the highest points of the wave (crest to crest) is known as the wavelength.  So a water disturbance with 200 ripples that passes a given point in one second would carry more energy (and consequently be more dangerous to humans) than a water disturbance with 1 ripple per second.

Gamma-rays are at the upper echelon of dangerous waves.  X-rays come next, followed by UV and then visible light.  Radio waves, the stuff that makes Wi-Fi possible, is on the opposite end of the spectrum. In fact, according to the World Health Organization (WHO), exposure to Wi-Fi for one year is tantamount to the same radiation received from a 20 minute call on your cellphone.  There have been detailed studies on this – check who.int if you’re curious.

Which frequencies do Wi-Fi use and why?

Wi-Fi radio waves transmit data at two frequencies:

  • 2.4 billion cycles per second (2.4 GHz)
  • 5 billion cycles per second (5 GHz)

Billions of cycles per second is a high number but by comparison, X-rays are measured in exahertz.

That’s right I said EXA.  That’s a 1 with 19 freggin’ zeros after it.

These numbers represent the kind of radio waves that are exchanged between your wireless router and your wireless device.

The reason computers get 2.4 Ghz is simple:  The FCC (Federal Communications Commission) said so.  Period.

Haha, it must feel good to have the power of the FCC.

The FCC apportioned a narrow slice of the electromagnetic spectrum to the public called the Industrial, Scientific and Medical (ISM) radio bands.  ISM is a free radio band that the FCC gives you and basically says:

Hey, you’re free to use devices in the 2.4 Ghz frequency band (specifically between 2,400 Mhz and 2,483.5 Mhz).  You don’t need a license to do this. Why?  Because we’re the FCC and we’re nice people.

It’s like the Autobahn in Germany.  You can do what you want on these roads.  Want to blaze up the asphalt in your new Nissan GTR Nismo?  Go ahead, no one will stop you.

Let freedom reign!

Image credit trombone65 (PhotoArt Laatzen) via Flickr

The low-barrier to entry set by the FCC; namely, not needing a license, means all the tech companies can create gadgets that live in the 2.4 Ghz space.

The radio bands are the arenas vendors vie for their device communication rights.

Wi-Fi characteristics

The higher the frequency the shorter the range but the more data can be transmitted.  Also the antenna sizes of transmitting devices are inversely proportional to frequency.  In other words, the higher the frequencies the shorter the required antenna.

Despite what that Ad says, “Size does matter”

The reason some devices use 2.4 GHz rather then some other number is because the FCC needed to find a way to wedge in a frequency band without affecting neighboring frequencies.  Microwaves already operated in 2.45Ghz space so the FCC said something like this:

Hey, let’s put the ISM band next to Microwaves.  We’ll cushion it with a few Mhz of space on each side to mitigate interference and then call it a day.  All the rogue gadgets out there can fight for space in the unlicensed 2.4 Ghz band and all our existing licensed devices will continue to work!

5Ghz is even better than the 2.4 Ghz band because it’s not susceptible to interface from RF signals generated from microwaves, baby monitors and wireless keyboards.  Also the 5Ghz band (technically 5.1 to 5.8 Ghz) is a wider frequency range than the 2.4 range.  So you can have more concurrent non-overlapping channels.

This means the din of college students who stream and blast Spotify tunes in the apartment above you won’t get in the way of your streaming Netflix videos of The Notebook.

The 2.4Ghz band only gives you three channels: 1, 6 and 11.  You can use all three but they can’t overlap.  Conversely, the 5Ghz band gives you 23 non-overlapping channels so you have more room indeed.

The only real problem with the 5Ghz band is that these devices cost more and the signals don’t carry quite as far as 2.4Ghz.

Wi-Fi IEEE standards

A consortium of talented geeks called the Institute of Electrical and Electronics Engineers (IEEE) established a set of standards to govern Wi-Fi specifications.  These specifications include everything from how data is exchanged, the nuances of frame lengths, encoding algorithms and a bunch of other stuff that might put you into a coma if if I listed them all.

Here’s what you need to know for your Jeopardy question with Alex:

802.11b is the oldest Wi-Fi you’ve probably heard of – circa 2000.  It tops out at 11 Megabits per second and is basically obsolete.

802.11a strutted into the world around the same time as 802.11b.  It loiters in the 5.8 Ghz frequency band and lets you transmit data up to 54 Mbits/second (but in practice, actually tops out around 22Mbits/second). The 54 limit is purely theoretical not actual.  Part of the problem with 802.11a is that the waves are absorbed easier by walls and other objects because of the shorter wavelengths.

802.11g showed up in the summer of 2003.  It’s like a mashup between 802.11b and 802.11a.  It uses the 2.4 Ghz band of 802.11b but also yields the same high-speed data transmission scheme of 802.11a.  So you get the best of both worlds.

The problem with 802.11g is that it’s backward comparability with 802.11b meant the total throughput in the wireless local area network (WLAN) could drop to the tortoise speeds of 11Mbps whenever a legacy client connected to the network.

That kind of sucks.

802.11n owes it’s claim to fame to a technology called multiple-input multiple-output antennas (MIMO).  Just imagine taking a bunch of transmit and receive antennas and grouping the whole thing into a super antenna.

With 802.11n you get four simultaneous data streams which gives you a maximum supported speed of 600Mbits/s.

802.11ac

802.11ac is basically MIMO on steroids.

It uses multi-user MIMO (MU-MIMO) – by the way, this acronym sounds funny “Moo Me Moh”.

MU-MIMO comprises multiple multiples of antennas spread out over different access points and radio terminals that each have a bunch of antennas.  Consequently, all this craziness multiples the confusion too, but the bottom line is that 802.11ac gives you even wider channels which translates to a maximum theoretical throughput of 1.3 Gbps.

802.11vh

This standard is in the draft form and currently allows maximum throughputs of up to 100TB/second.  That’s 100 Terabits per second for the weary eyed.  It’s called the 802.11vh standard because it is an imaginary standard designed by yours truly Vonnie Hudson!

Hahahah okay I’m done being goofy I promise.

Stay tuned for part 2 of 3.  It comes out tomorrow around 6am EST.

I’ll break down exactly how radio waves can carry complex sets of information like the JPEGs of your cat.

Then in the last part, part 3, I’ll teach you the truth behind Wi-Fi hotspots and the explore the turbid waters of Wi-Fi security.  I’ll debunk a bunch of myths and then show you how to stay safe and sound when working wirelessly.

The Bottom Line

Wi-Fi is pretty interesting when you consider how it works.  After reading this article you should:

  • Have a keen understanding about the basics of electromagnetic radiation (and wonder why you wasted physics class blowing spitballs at little Johnny; seriously, what did he ever do to you?)
  • Know everything you need about radio waves and frequencies
  • Have a foundation for why the FCC picked the 2.4 and 5Ghz frequency bands (now that I think about it, 2.4Ghz would be a cool name for a rock band, anyone know if one exists by that name?)
  • Grasp the different 802.11 varieties

In the next guide we’ll explore how meaningless radio waves can become meaningful.  In other words, how do radio waves carry information such as HD videos from Youtube?

We’ll also explore the truth behind Wi-Fi hotspots and show you how to secure your Wi-Fi networks from your intrusive neighbors.

Stay tuned kid – I’m having fun writing this stuff (I hope you’re having fun reading it)

It’s about to get good.

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