WEBVTT 0:00:03.180000 --> 0:00:07.060000 Hello and welcome this video, which is a review of Wi-Fi. 0:00:07.060000 --> 0:00:10.420000 We're not going to be getting into wireless LANs and Wi-Fi concepts spread 0:00:10.420000 --> 0:00:13.200000 out across several different videos. 0:00:13.200000 --> 0:00:19.540000 So let's just start with a real hi-fi, hi-fi, Wi-Fi overview. 0:00:19.540000 --> 0:00:21.040000 It's been a long day already. 0:00:21.040000 --> 0:00:25.400000 So we're going to start with what is Wi-Fi and sort of do a high level 0:00:25.400000 --> 0:00:28.240000 overview of Wi-Fi standardization. 0:00:28.240000 --> 0:00:30.100000 So what is Wi-Fi? 0:00:30.100000 --> 0:00:31.480000 It is not an acronym. 0:00:31.480000 --> 0:00:34.460000 It doesn't mean wireless fidelity or anything of that nature. 0:00:34.460000 --> 0:00:36.860000 It's just a, it's a brand name is what it is. 0:00:36.860000 --> 0:00:39.020000 It's a brand name for wireless. 0:00:39.020000 --> 0:00:40.680000 That's all it is. 0:00:40.680000 --> 0:00:43.660000 Well, Wi-Fi really boils down to is like it says, the manipulation of 0:00:43.660000 --> 0:00:48.060000 an electromagnetic radiation to encode data. 0:00:48.060000 --> 0:00:57.080000 So here's the way to think about it. 0:00:57.080000 --> 0:00:59.460000 Believe it or not, now I'm not a physicist. 0:00:59.460000 --> 0:01:00.480000 I'm not a scientist. 0:01:00.480000 --> 0:01:03.200000 I've done like this much research into it. 0:01:03.200000 --> 0:01:07.720000 But I can tell you that I read, which is sort of blew my mind, that the 0:01:07.720000 --> 0:01:13.260000 theory behind radio frequency is that if you take, for example, a copper 0:01:13.260000 --> 0:01:17.960000 cable, like a strand of wire or even a coat hanger for that matter. 0:01:17.960000 --> 0:01:21.160000 And if you could run alternating current through that, as that current 0:01:21.160000 --> 0:01:25.000000 is going back and forth, alternating current as a byproduct of that, it 0:01:25.000000 --> 0:01:30.000000 actually emits electromagnetic radiation from that wire. 0:01:30.000000 --> 0:01:32.580000 That's how easy it is to create Wi-Fi. 0:01:32.580000 --> 0:01:35.400000 And in a simple experiment, you could probably recreate that with like 0:01:35.400000 --> 0:01:38.460000 a coat hanger and some batteries or something of that nature. 0:01:38.460000 --> 0:01:41.880000 Although I'm not sure how you would test that it was actually emitting 0:01:41.880000 --> 0:01:42.980000 the information. 0:01:42.980000 --> 0:01:45.480000 But still, that's what Wi-Fi is. 0:01:45.480000 --> 0:01:51.500000 So, electromagnetic radiation has both an electrical component and a magnetic 0:01:51.500000 --> 0:01:52.720000 component of it. 0:01:52.720000 --> 0:01:55.980000 Now, certainly at the CCE level, we don't have to get into the gory guts 0:01:55.980000 --> 0:01:58.380000 and detail of the science behind this. 0:01:58.380000 --> 0:02:03.980000 But what's kind of cool is that we can manipulate certain properties of 0:02:03.980000 --> 0:02:08.600000 this electromagnetic radiation to actually encode your ones and zeros 0:02:08.600000 --> 0:02:09.700000 to encode your data. 0:02:09.700000 --> 0:02:13.780000 And that's what Wi-Fi is really all about. 0:02:13.780000 --> 0:02:18.320000 So, the electromagnetic radiation that we're dealing with is known as 0:02:18.320000 --> 0:02:19.560000 radio frequencies. 0:02:19.560000 --> 0:02:20.380000 Now, why do we call that? 0:02:20.380000 --> 0:02:25.160000 Because there's a huge spectrum of electromagnetic radiation, you know, 0:02:25.160000 --> 0:02:28.740000 way at the top. And there's like gamma rays, which go through everything 0:02:28.740000 --> 0:02:29.960000 in the universe. 0:02:29.960000 --> 0:02:32.140000 And then, you know, way down towards the bottom, we have like ultraviolet 0:02:32.140000 --> 0:02:37.800000 light. And then we have, it's just a huge range of electromagnetic energy. 0:02:37.800000 --> 0:02:42.720000 And certain pieces of that within that range are what we utilize as radio 0:02:42.720000 --> 0:02:47.800000 frequencies. Now, sometimes Wi-Fi has been known to be called wireless 0:02:47.800000 --> 0:02:52.620000 ethernet. You don't hear that so much anymore, but it is absolutely not 0:02:52.620000 --> 0:02:54.000000 wireless ethernet. 0:02:54.000000 --> 0:03:00.100000 It has some characteristics of wireless ethernet only in the sense of 0:03:00.100000 --> 0:03:11.300000 that, like in the old collision domain, like connected to a hub, for example. 0:03:11.300000 --> 0:03:14.960000 And in that environment, only one device could talk at a time. 0:03:14.960000 --> 0:03:18.840000 That's pretty much where Wi-Fi and ethernet sort of, that's pretty much 0:03:18.840000 --> 0:03:20.200000 all they have in common. 0:03:20.200000 --> 0:03:25.280000 The framing structure of Wi -Fi is totally different. 0:03:25.280000 --> 0:03:29.180000 How it detects and reacts to collisions is totally different. 0:03:29.180000 --> 0:03:33.400000 It's not wired, it's not wireless ethernet. 0:03:33.400000 --> 0:03:38.980000 Okay, so over time, the IEEE has created these various different working 0:03:38.980000 --> 0:03:41.840000 groups, just like they created a working group for Ethernet, which was 0:03:41.840000 --> 0:03:46.360000 802.3. And they got working groups for other standards like token ring 0:03:46.360000 --> 0:03:48.800000 and fitting and stuff which aren't around anymore. 0:03:48.800000 --> 0:03:53.040000 They have created over the last few decades different working groups dedicated 0:03:53.040000 --> 0:03:59.980000 towards Wi-Fi, increasing the security of Wi-Fi, making Wi-Fi faster, 0:03:59.980000 --> 0:04:03.760000 adding the ability for multiple devices to transmit at one time and all 0:04:03.760000 --> 0:04:05.820000 kinds of things. 0:04:05.820000 --> 0:04:09.620000 So these are all through the IEEE. 0:04:09.620000 --> 0:04:13.420000 And so Wi-Fi standardization, a lot of times these working groups focus 0:04:13.420000 --> 0:04:17.420000 on one of sort of two components of Wi-Fi. 0:04:17.420000 --> 0:04:20.980000 The physical layer, so those will be the working groups involved with 0:04:20.980000 --> 0:04:24.980000 how do we make Wi-Fi faster? 0:04:24.980000 --> 0:04:27.380000 How do we make antennas better? 0:04:27.380000 --> 0:04:30.920000 How do we make the transmitters more powerful or cleaner to where they 0:04:30.920000 --> 0:04:32.920000 can transmit further? 0:04:32.920000 --> 0:04:39.020000 How do we do, how do we come up with more creative ways to manipulate 0:04:39.020000 --> 0:04:44.380000 the radio frequencies so we can encode more data into that radio frequency? 0:04:44.380000 --> 0:04:48.120000 That's all physical layer or phi layer stuff. 0:04:48.120000 --> 0:04:51.000000 And some working groups have just focused on that. 0:04:51.000000 --> 0:04:54.620000 Other working groups have focused more on the Mac layer. 0:04:54.620000 --> 0:04:59.960000 For example, introducing newer and better and stronger ways of Wi-Fi security 0:04:59.960000 --> 0:05:03.220000 would be considered something at the Mac layer as well as other types 0:05:03.220000 --> 0:05:07.860000 of things. So originally the original working group was the 802.11 working 0:05:07.860000 --> 0:05:16.300000 group. So just like we think of 802 .3 as being wired lands or ethernet, 0:05:16.300000 --> 0:05:21.160000 802.11 is the overall umbrella term for Wi-Fi. 0:05:21.160000 --> 0:05:24.860000 And then underneath 802.11 we have various sub working groups that create 0:05:24.860000 --> 0:05:32.940000 things. So when 802.11 first came out, Wi-Fi was known as 802.11, that 0:05:32.940000 --> 0:05:37.320000 was it. And then as they subsequently started revising and adding it, 0:05:37.320000 --> 0:05:41.900000 there would be these subcommittees like the 802.11 B subcommittees. 0:05:41.900000 --> 0:05:43.280000 And then the G subcommittees. 0:05:43.280000 --> 0:05:46.380000 And these days, if you know anything about Wi-Fi, you've probably heard 0:05:46.380000 --> 0:05:50.960000 of like the 802.11 AX subcommittees and AD sub... 0:05:50.960000 --> 0:05:55.760000 So these are all under the umbrella of the 802.11 working group. 0:05:55.760000 --> 0:05:58.680000 So this first started in 1997. 0:05:58.680000 --> 0:06:00.420000 That's when it very first came out. 0:06:00.420000 --> 0:06:04.780000 Back then Wi-Fi was an amazing like one point something megabits per second. 0:06:04.780000 --> 0:06:07.660000 But it was still very cool, this concept of, hey, we've developed a way 0:06:07.660000 --> 0:06:10.000000 to use radio frequencies to encode data. 0:06:10.000000 --> 0:06:11.080000 How cool is that? 0:06:11.080000 --> 0:06:16.160000 And then a couple years later, a sub committee 802.11 B came out and they 0:06:16.160000 --> 0:06:20.320000 said, hey, we can now increase the speed of Wi-Fi to 10 megabits per second. 0:06:20.320000 --> 0:06:22.680000 Whoa, amazingly fast. 0:06:22.680000 --> 0:06:26.220000 And then over time, it's just gotten faster and stronger and better, just 0:06:26.220000 --> 0:06:29.640000 like the $6 million man, for those of you old enough to remember that. 0:06:29.640000 --> 0:06:34.460000 So here are some of the five standards by far, not all of them. 0:06:34.460000 --> 0:06:35.180000 There are so many. 0:06:35.180000 --> 0:06:37.900000 A lot of times they get into double digits. 0:06:37.900000 --> 0:06:43.880000 But you can see the maximum theoretical data rates have just increased 0:06:43.880000 --> 0:06:46.460000 and increased and increased over time. 0:06:46.460000 --> 0:06:51.380000 You can see the date when these standards were formally adopted. 0:06:51.380000 --> 0:06:54.760000 And you can see the frequencies that these were on. 0:06:54.760000 --> 0:06:57.760000 So let's just talk real quickly about what does that mean by frequency. 0:06:57.760000 --> 0:07:01.380000 Well, think about it like this. 0:07:01.380000 --> 0:07:06.120000 If you're not even familiar with that word frequency, frequency is just 0:07:06.120000 --> 0:07:08.960000 a general term. It's a measurement term. 0:07:08.960000 --> 0:07:13.300000 It's a measurement term for measuring how often something changes over 0:07:13.300000 --> 0:07:16.060000 time. So if you're going to measure how often something changes, you're 0:07:16.060000 --> 0:07:17.880000 going to measure the frequency of that. 0:07:17.880000 --> 0:07:24.620000 Now, the typical unit of measurement and frequency is the Hertz. 0:07:24.620000 --> 0:07:30.240000 Okay? So I may not have that acronym entirely correct there. 0:07:30.240000 --> 0:07:34.160000 Oh, it's just HZ, the Hertz. 0:07:34.160000 --> 0:07:40.720000 So 1 Hertz is equal to something changing one time per second. 0:07:40.720000 --> 0:07:45.220000 So if I'm able to spell out the alphabet and each letter I'm saying once 0:07:45.220000 --> 0:07:49.120000 a second, I'm speaking or I'm changing the letters at 1 Hertz. 0:07:49.120000 --> 0:07:55.040000 Well, radio frequencies, we manipulate the radio frequency. 0:07:55.040000 --> 0:07:58.560000 So they change at a predictable rate. 0:07:58.560000 --> 0:08:03.020000 Okay? And remember, electromagnetic radiation can change and when it's 0:08:03.020000 --> 0:08:07.340000 changing super fast, it's like gamma radiation and x-rays, the frequency 0:08:07.340000 --> 0:08:10.380000 of that is just off the charts. 0:08:10.380000 --> 0:08:14.300000 So many, you know, it's gazillions of times per second. 0:08:14.300000 --> 0:08:18.240000 And then we have, for example, well, voice, right? 0:08:18.240000 --> 0:08:25.820000 Audio voice. I remember hearing somewhere that the lowest audible tone, 0:08:25.820000 --> 0:08:32.440000 I think that the human ear can hear was like either 20 kilohertz or 20 0:08:32.440000 --> 0:08:35.760000 megahertz, but the lower you go. 0:08:35.760000 --> 0:08:41.700000 So if you're talking about audio tone or sound tone, the lower the frequency, 0:08:41.700000 --> 0:08:45.340000 the lower it is, the higher the frequency, the higher it is. 0:08:45.340000 --> 0:08:50.520000 So when you're changing your voice, you know, your vocal cords are going 0:08:50.520000 --> 0:08:52.340000 back and forth at a different frequency. 0:08:52.340000 --> 0:08:56.920000 So what this is talking about is certain frequency bands were used for 0:08:56.920000 --> 0:08:59.860000 Wi-Fi, for radio frequency. 0:08:59.860000 --> 0:09:04.560000 So one band is a 2.4 gigahertz band, which means that all the Wi-Fi that 0:09:04.560000 --> 0:09:09.740000 operates in that band is manipulating or, I'll just say manipulating the 0:09:09.740000 --> 0:09:15.460000 radio frequency is changing it right around 2.4 billions of changes per 0:09:15.460000 --> 0:09:20.240000 second. So 2 billion, 400 million changes per second. 0:09:20.240000 --> 0:09:22.240000 That is 2.4 gigahertz. 0:09:22.240000 --> 0:09:24.720000 And a lot of Wi-Fi channels are in that range. 0:09:24.720000 --> 0:09:29.240000 And then other Wi-Fi standards shows a different range, which is 5 gigahertz 0:09:29.240000 --> 0:09:34.880000 or 5 billion changes per second of that radio wave. 0:09:34.880000 --> 0:09:38.180000 So that is our first introduction to Wi-Fi. 0:09:38.180000 --> 0:09:42.400000 And we've sort of tasted how Wi-Fi was standardized and how some of these 0:09:42.400000 --> 0:09:45.860000 standards have changed and grown over time. 0:09:45.860000 --> 0:09:48.720000 So in the subsequent videos, we're going to get into more detail about 0:09:48.720000 --> 0:09:51.320000 practical Wi-Fi usage. 0:09:51.320000 --> 0:09:53.520000 What are the components in Wi-Fi networks? 0:09:53.520000 --> 0:09:55.300000 How do we implement security? 0:09:55.300000 --> 0:09:56.380000 And we're going to look at that. 0:09:56.380000 --> 0:09:57.660000 So stay tuned for those videos.