WEBVTT 00:00:00.800 --> 00:00:17.560 Hello everyone and welcome to a wireless section in your Encore course. Now Raymond is taking you 00:00:17.560 --> 00:00:24.520 through networking with various wired solutions. We are now going to begin talking about a wireless 00:00:24.520 --> 00:00:30.440 portion. Now this is recorded only. Hopefully you guys have taken the time to view this obviously. 00:00:31.320 --> 00:00:36.680 But the reason we are doing this as an addendum is because there's so much here in wireless that 00:00:36.680 --> 00:00:42.840 it would be tough to cover in a live course and tough to cover well. Wireless is something I've 00:00:42.840 --> 00:00:48.200 taught several times in my career obviously but it's something that is a very tough technology 00:00:48.200 --> 00:00:57.000 to get right. It's its own CCIE discipline. It is very difficult from a perspective of 00:00:57.000 --> 00:01:02.360 understanding how the signal flows through the medium of air. So what we're going to do is we're 00:01:02.360 --> 00:01:08.840 going to focus, hyper focus on the certifications and what's required to actually pass the exam. 00:01:08.840 --> 00:01:13.960 Now if you want to dive into the wireless technology and I like it, it's one of my favorite 00:01:13.960 --> 00:01:21.640 things, you should. But right now what we're going to do is we're going to dive into just what you 00:01:21.640 --> 00:01:26.600 need to know for the certification. I'm going to show you different websites and things like that 00:01:26.600 --> 00:01:32.200 to dive into but let's go ahead and go into our first lesson. Our first lesson is all about layer 00:01:32.200 --> 00:01:37.160 one wireless. Now I do need to give you some background information here when we're going 00:01:37.160 --> 00:01:43.240 through wireless and how it works. So some of this stuff will not be exam relevant but you need to be 00:01:43.240 --> 00:01:51.160 able to understand it for the exam. So let's jump into what wireless is. First off, wireless is 00:01:52.600 --> 00:01:57.880 is a signal. That's all it is. We have signals that go along copper lines but now we have signals that 00:01:57.880 --> 00:02:05.560 go in the air. We are pushing this out into everything around you. Wireless signals are 00:02:05.560 --> 00:02:14.360 flying around from everything like audio. Someone just speaking. Looks like I forgot to press the 00:02:14.360 --> 00:02:21.640 button. So let's go back to this. Let me press the button and hopefully it'll let me draw. Yes, okay. 00:02:21.640 --> 00:02:28.440 So audio is the first. The voice right now, what you're hearing is a signal, believe it or not, is a 00:02:28.440 --> 00:02:35.080 wireless transmission. We're doing wireless communication right now. The sound, it carries 00:02:35.640 --> 00:02:38.760 a signal to your eardrums and that vibration is then 00:02:41.240 --> 00:02:49.480 is then understood by your brain and then your brain turns it into a meaning, right? This is not 00:02:49.480 --> 00:02:55.800 all that different from the wireless we receive here, this spectrum. Now this is from, we'll talk 00:02:55.800 --> 00:03:03.000 a little bit about this, but this is from 2.4 to 6 gigahertz. Now 6 gigahertz is a new range but 00:03:03.000 --> 00:03:09.240 that's kind of where we are right now with wireless. We have these bands that are specific 00:03:09.240 --> 00:03:14.840 for wireless communication and the reasoning for that is why don't we use all of this? Why 00:03:14.840 --> 00:03:20.280 aren't we using in the terahertz or the petahertz or the exahertz? Why aren't we going way up the 00:03:20.280 --> 00:03:26.760 scale, right? That means that's more data we could throw. No, the reason is there are 00:03:26.760 --> 00:03:34.040 different things that live in these areas. Here we're talking about light and here's where humans 00:03:34.040 --> 00:03:41.480 can see. This is the visible spectrum. We can start seeing those wavelengths. Here we have 00:03:41.480 --> 00:03:48.680 microwaves and things like that. That's why a microwave is a huge bit of trouble in your 00:03:48.680 --> 00:03:56.680 wireless environments if it's leaking. We've got TV, we've got FM radio, we've got AM radio, 00:03:56.680 --> 00:04:03.560 ampular and frequent modulation. We've got another TV band here. Even in this range right here, 00:04:03.560 --> 00:04:10.440 we have some emergency communication depending on where you are. So we have lots of these waves and 00:04:10.440 --> 00:04:18.360 since we share the same medium, since it's all in the air, you are overlapping with other frequencies 00:04:18.360 --> 00:04:24.040 the key is we can't use the same frequency at the same time. Once you start doing that, it creates 00:04:24.040 --> 00:04:32.360 interference. So I'd like to show you what this kind of looks like in our frequency bands. 00:04:32.360 --> 00:04:39.640 If we're looking at our frequency bands and what different wireless protocols use, 802.11a, 00:04:39.640 --> 00:04:45.880 the first kind of real standard we were using, was at 5 gigahertz and then the 802.11b started 00:04:45.880 --> 00:04:52.920 using the 2.4 gigahertz and then 802.11g is 2.4. Now a lot of you guys are probably wondering, 00:04:52.920 --> 00:04:59.160 what's the difference? Why does it matter if I'm using 5 or 2.4? Well, 2.4 is an actually, 00:04:59.160 --> 00:05:05.960 it's a longer wavelength. Remember, this is frequency. When I draw a wavelength, this is 00:05:06.840 --> 00:05:12.360 the frequency from here to here, from the top point to the top point. How fast does that happen? 00:05:12.920 --> 00:05:19.640 Hertz. It's how many times per second. So this gigahertz, we're talking thousands of times per 00:05:19.640 --> 00:05:27.080 second. 5 gigahertz, this little cycle right here, from here to here, will happen twice as fast 00:05:27.080 --> 00:05:34.280 as it does in a 2.4 gigahertz. So what we're seeing is we're seeing shorter wavelengths, 00:05:34.360 --> 00:05:39.800 more energy going into it. What that means is the distance is shorter 00:05:41.240 --> 00:05:50.520 for 5. It's a shorter distance. 2.4 can travel in longer distances. 00:05:51.720 --> 00:05:59.880 But here's an interesting thing to remember. If I can travel a shorter distance, but I'm going 00:05:59.960 --> 00:06:06.360 twice as fast, the frequency is jumping up and down twice as fast, I can move more data. 00:06:07.880 --> 00:06:12.520 Now there's a lot that goes into how much data you can move at any given time, 00:06:12.520 --> 00:06:18.600 but that's the general gist of it, right? There's scatter, there's interference, 00:06:18.600 --> 00:06:22.680 there's things that come into play on how much data you can actually move. But in general, 00:06:22.680 --> 00:06:27.480 if you are close enough for the AP to 2.4 and 5 gigahertz to be effective, 00:06:27.480 --> 00:06:33.320 5 gigahertz will transmit more data. And you can kind of see this. If we look at this, 802.11a was 00:06:33.320 --> 00:06:39.800 54 megabits per second. When we went to B, look at the drop, 11 megabits per second. But we got 00:06:39.800 --> 00:06:46.120 more distance out of that. When we go back to G, we're seeing 2.4 at 54 megabits per second. 00:06:46.120 --> 00:06:49.480 They were more efficient, there were algorithms employed, there's different things like that. 00:06:50.040 --> 00:06:56.360 Then we got to N. N is when we started saying, oh, we'll use both. We'll use 2.4 and 5. This 00:06:56.360 --> 00:07:03.000 is more for backwards compatibility at the time. And then we saw a jump to 450 megabits per second. 00:07:03.000 --> 00:07:09.720 Compare that to the other speeds we're seeing, right? That's a huge leap. It's almost tenfold. 00:07:11.240 --> 00:07:17.800 Then we start to get into AC. Some of you out there will call it Wi-Fi 5. That's when we really 00:07:17.800 --> 00:07:23.560 started using that naming convention. And that was at 5 gigahertz. And look at the speed, 00:07:23.560 --> 00:07:29.960 up to 7 gigabits. Now, there's a big asterisk next to all these speeds. We'll talk about it a 00:07:29.960 --> 00:07:36.040 little later. But that was a theoretical top of where you could get. Not really what you're seeing 00:07:36.040 --> 00:07:42.040 in the real world. But that's what in labs, when there's no interference, when you're standing 00:07:42.040 --> 00:07:47.880 right next to the AP, that's the kind of speed you could expect. Now, when we look at AX, this 00:07:47.880 --> 00:07:55.880 is called 6. And we'll talk about 6E in a second. I didn't forget. You get 2.4 and 5 for the original 00:07:55.880 --> 00:08:04.200 AX or Wi-Fi 6. That had a speed up to 10 gigabits per second in a lab environment again. And then 00:08:04.200 --> 00:08:10.840 we introduced 6E. That's a second standard. It's still qualified under the AX. But it was a new 00:08:10.840 --> 00:08:17.640 standard that was released by the Wi-Fi group. This allowed us to get to 10 gigabit-ish, 00:08:18.200 --> 00:08:23.560 right in there, 9.1 or something like that, gigabits per second. And this, again, 00:08:23.560 --> 00:08:28.520 was in the lab environment. But what this represented was a drastic increase in speed 00:08:30.040 --> 00:08:36.200 and real world speed at that, not just in the lab. The theoretical top limit was the same. 00:08:36.200 --> 00:08:42.920 But as we moved forward with the 6 gigahertz range, we started to see improvements in real 00:08:42.920 --> 00:08:50.600 world speed. And that brings us up to the newest, latest, and greatest 802.11 BE. Everybody you know 00:08:50.600 --> 00:08:59.720 will call it Wi-Fi 7. Wi-Fi 7 uses all of these. It has radio wave standards. It's got new algorithms. 00:08:59.720 --> 00:09:06.760 It's got more antennas supported. All those things do not necessarily translate into everyone's 00:09:06.760 --> 00:09:14.200 device because devices need specific antennas that are enabled for the BE or 7 standard. 00:09:14.200 --> 00:09:22.040 So just because it says, I believe it's 8x8 or 16x16, antennas does not mean that's supported 00:09:22.040 --> 00:09:26.600 and does not mean you get to use all those antennas. I really suggest you dive into a 00:09:26.600 --> 00:09:31.160 wireless class here. There's a lot of marketing that takes place that kind of 00:09:33.000 --> 00:09:40.200 rolls over into wireless purchases that don't necessarily translate into speeds for your users. 00:09:40.200 --> 00:09:46.040 So something to pay attention to. Now, the important part of wireless 00:09:46.840 --> 00:09:53.080 is understanding the signal you're receiving. That's really where we need to pay attention 00:09:53.080 --> 00:09:59.000 in our wireless environments. Obviously right now even, if you look in the lower right hand 00:09:59.000 --> 00:10:02.920 side of your computer, you're probably going to see a signal strength indicator. 00:10:03.720 --> 00:10:14.360 What that kind of goes on is this. It's really all about measuring dBms, decibel per milliwatt or 00:10:14.360 --> 00:10:20.840 decibel milliwatts. So what this is, is the power you are putting into the signal and projecting it 00:10:20.920 --> 00:10:30.440 out. Decibel is a generic way to measure things by strength. I'm not going to dive into it. That's 00:10:30.440 --> 00:10:37.880 a deep wireless class. But decibel is just a reference measurement. So if I start somewhere 00:10:39.000 --> 00:10:46.520 and I increase the decibels, I am increasing that relative to where I began. So if I have 00:10:46.520 --> 00:10:53.960 a measurement on how much power I'm actually putting into the air or the signal, I can then 00:10:53.960 --> 00:11:01.400 transfer it into a decibel. So when I say dBm, that's decibel milliwatts, that is the increase 00:11:01.400 --> 00:11:09.800 or decrease of power based on my reference point. So decibels to a milliwatt. Please remember that. 00:11:09.800 --> 00:11:15.960 And also, please remember that these are usually, almost always, measured in a negative. 00:11:17.720 --> 00:11:24.040 Now, why a negative? Well, if you think about it, if it is a reference measurement and I'm 00:11:24.040 --> 00:11:29.640 going through the air, I'm going down a cable, I'm doing things. Think of it like friction 00:11:30.200 --> 00:11:36.520 here on earth. If I drag a mouse across the table, there's friction and the energy I put in 00:11:37.080 --> 00:11:44.360 is kind of drawn down. That scraping across the table creates a little bit of drag, which means 00:11:44.360 --> 00:11:50.040 the energy I'm putting in the mouse is not actually everything I'm getting when I move 00:11:50.040 --> 00:11:57.320 the mouse. I'm getting only a percentage of what I put in. And that's what we're seeing with dBm, 00:11:57.320 --> 00:12:04.440 decibel to milliwatts. I put in 100,000 watts and I throw it out in the air. When somebody is 00:12:04.440 --> 00:12:09.320 receiving a signal, they're not receiving 100,000 watts. Because think of it this way, 00:12:09.320 --> 00:12:14.840 it goes up the antenna, it goes everywhere. You're only receiving a small fraction of that. 00:12:14.840 --> 00:12:19.720 So you're not going to receive the full signal transmission. That's why we measure this in 00:12:19.720 --> 00:12:25.880 negatives because you're losing signal. Now, how much you lose is very important to keep track of. 00:12:27.000 --> 00:12:33.160 And I'd be remiss if I didn't say this, some vendors drop the negative because it's confusing 00:12:33.160 --> 00:12:41.240 to people. They shouldn't, but they do. So there we go. So dBm, decibel to milliwatt, 00:12:41.240 --> 00:12:48.200 it's the easiest and most consistent way to use this. Not all people pay attention to it. 00:12:50.280 --> 00:12:56.200 You'll see some vendors not use dBm, but for this, for your understanding, dBm is the easiest 00:12:56.200 --> 00:13:03.160 way to get there. So strength of the signal. Like we talked about, this gives me an idea. 00:13:03.880 --> 00:13:07.560 When we're talking about dBm, we're talking about signal strength. 00:13:07.560 --> 00:13:17.080 Now, here's an important thing to understand. If a signal has plus 3 dBm, we are adding signal 00:13:17.080 --> 00:13:25.560 strength. So plus, we are going up. And like we just said, negative means the signal strength 00:13:25.560 --> 00:13:39.720 is dropping. So if I say, I'm going to put, we got 20 dB going out right now. I'm going to put it to 23. 00:13:40.120 --> 00:13:47.960 What have I done to that signal? Well, let's say, and please, we're just using numbers here. 00:13:47.960 --> 00:13:53.960 Let's say this is 100 watts of power I'm putting into it. Don't think about this too much. Okay, 00:13:53.960 --> 00:14:02.280 that's way too much power. But if I put 100 watts into the air there, if I go to 23, 00:14:02.600 --> 00:14:08.680 that's 200 watts, roughly. This is a power of 3. There's an actual equation that you don't 00:14:08.680 --> 00:14:14.120 need to memorize. But this is what I would like you to remember. And very important, 00:14:14.120 --> 00:14:21.960 if I was going to sit and take some type of exam on this, is I would definitely understand that 00:14:21.960 --> 00:14:27.240 plus 3, signal's going up by double the power. Minus 3, I'm dropping power in half. 00:14:27.240 --> 00:14:34.680 Very important to realize and understand. Next up is our Received Signal Strength Indicator, 00:14:34.680 --> 00:14:42.600 RSSI. It's important to understand here that this is not standardized. There's no Wi-Fi body 00:14:42.600 --> 00:14:52.200 or approval or, this is not an open standard published by IANA or any other organization. 00:14:52.200 --> 00:15:01.240 It's not an open standard published by IANA or any of the other major internet providers, 00:15:01.240 --> 00:15:08.760 even the Wi-Fi Council. But it is a way that a lot of people measure this. Indicators 0 to 60 00:15:08.760 --> 00:15:15.720 in some vendors, 0 to 255 by some vendors. And this will determine that little Wi-Fi signal thing 00:15:16.280 --> 00:15:22.040 if you're watching this on wireless. This is what a lot of vendors use to determine, 00:15:22.040 --> 00:15:26.200 oh, your Wi-Fi signal is low. You only have one bar or six bars or whatever. 00:15:26.200 --> 00:15:30.280 This is not a standardized issue. I just want you to be aware that it's there. 00:15:31.640 --> 00:15:40.840 So let's dive into signal strength. So we talked about negative 30 dB or 30 dB or how these ratings 00:15:40.840 --> 00:15:45.800 are all negative. Let's talk about negative 30, the very top, and we'll jump to the very bottom. 00:15:45.800 --> 00:15:51.240 It's important you understand this list, by the way, understand what's ranking here, 00:15:51.240 --> 00:15:57.000 and we'll go through it a little bit. But let's start at top and bottom. Negative 30 dBm. I know 00:15:57.000 --> 00:16:01.880 what you're saying, negative 30. Goodness gracious, you've lost a lot of power from 00:16:01.880 --> 00:16:09.880 that antenna. You're receiving negative 30 from zero. That signal strength has dropped quite a 00:16:09.880 --> 00:16:18.520 bit. But remember, let's talk about what we said earlier, where that signal is being pushed out in 00:16:18.520 --> 00:16:26.120 every direction, in a direction through a wireless space. So you're pushing this signal through the 00:16:26.120 --> 00:16:31.480 air towards a direction, or in some case in an omni-directional, in every direction. 00:16:32.520 --> 00:16:38.200 So people will only receive a fraction of the signal you are sending out. Negative 30 dBm is 00:16:38.200 --> 00:16:46.120 amazing. That means you are likely sitting next to the AP. You're right next to the AP. This is 00:16:46.760 --> 00:16:53.480 basically lab environment type signal strength. You're not going to see this in an office 00:16:53.480 --> 00:16:59.720 environment or here or there or anywhere where there's interference. This is the golden standard, 00:16:59.720 --> 00:17:09.400 right? Let's talk about the bottom. Negative 90. Now remember, we drop by a power of 2 for 00:17:09.400 --> 00:17:18.040 every 3 dBm. And we've dropped 30 dBm. So that's 10 times you're having that signal. 00:17:18.920 --> 00:17:26.680 That's incredibly lower. It's a factor of 10 worse than the signal you received at the very best. 00:17:26.680 --> 00:17:33.720 This is unusable. Negative 90 means people are not connecting. The data is, you may get a 00:17:33.720 --> 00:17:40.440 connection and drop, connection and drop. It is not ideal for any type of data transfer. 00:17:41.160 --> 00:17:46.120 Okay, so let's go in the middle. What is good? What are we looking for? Well, VoIP, which is a 00:17:46.120 --> 00:17:52.680 very important, very resource-intensive streaming service, right? And then streaming video. Well, 00:17:52.680 --> 00:17:58.440 we only need negative 67 for that. Our signal strength, we've lost some signal, but we haven't 00:17:58.440 --> 00:18:04.680 lost at all. This is a very good, this is the top of the line. If you're getting negative 67 dBms, 00:18:05.240 --> 00:18:12.840 you're doing great. That's like a 4-bar, 5-bar situation whenever your operating system shows. 00:18:13.640 --> 00:18:19.800 Now 70 dBm, maybe you're a little farther away from the access point. Maybe you don't have great 00:18:19.800 --> 00:18:23.080 signal strength. Maybe there's a lot of interference and a lot of offices near you. 00:18:23.720 --> 00:18:30.280 Channels are overlapping for different SSIDs, and it's not a great system. 00:18:30.280 --> 00:18:34.920 You can still get on the web and you can still do email. That's usually the case. 00:18:36.040 --> 00:18:40.440 And then when we go to negative 80, that's not good at all. People are dropping in and out. 00:18:41.400 --> 00:18:47.640 Can't be used for VoIP, definitely. Can't be used for voice. Not good for web traffic. This is just 00:18:47.640 --> 00:18:51.160 bad. You don't want to download. You don't want to stream. Nothing even close here. 00:18:53.160 --> 00:19:03.640 Notice that from here to here, 67 to 70, what's our dB difference? Well, that's a negative 3, 00:19:03.640 --> 00:19:11.480 isn't it? We've dropped 3 more. And negative 3 means the signal is what? Halved. So from here 00:19:11.480 --> 00:19:21.880 to here, we've lost half the power of the signal. Okay, we're going to keep revisiting that just so 00:19:21.880 --> 00:19:27.080 you get an idea. You start getting that reference in your mind of how it works. 00:19:28.760 --> 00:19:34.120 So I mentioned something in the last slide that we need to really talk about. I said 00:19:34.120 --> 00:19:38.920 interference. You might have other channels or other things using the same frequency as you. 00:19:39.560 --> 00:19:47.080 This brings up a good question. How much is too much interference? Well, honestly, 00:19:47.080 --> 00:19:55.560 it depends on your signal and how much background noise, or in this case, noise we have in our 00:19:55.560 --> 00:20:06.120 environment. To figure this out is noise floor. That's here. This is the noise floor. And then 00:20:06.120 --> 00:20:12.840 you take out the received signal. Now remember, you receive all of the signal. 00:20:17.640 --> 00:20:23.000 And you need to take out – sorry, my shoulder's in the way. You need to take out the noise floor 00:20:23.000 --> 00:20:28.920 because really, this is only the viable signal you're going to receive. This area in here, 00:20:28.920 --> 00:20:33.960 like it says, SNR, the dB. That's what you're really going to see because the signal, the 00:20:33.960 --> 00:20:37.800 noise floor is going to cancel out any of the signal you have in the same space. 00:20:39.320 --> 00:20:43.560 Think about if I was talking very quietly and we were whispering about something, 00:20:44.280 --> 00:20:48.920 and then other people are whispering at the same time. You're not going to hear it. It cancels 00:20:48.920 --> 00:20:54.280 each other out. But as I raise my voice over that whispering or that background noise, 00:20:54.280 --> 00:20:58.440 you're going to hear me more and more. That's exactly the same as the signal you receive. 00:20:58.440 --> 00:21:02.360 And this is why the signal-to-noise ratio is a very important calculation. 00:21:03.320 --> 00:21:07.480 So how do we calculate this? Well, we take the signal and subtract the noise. 00:21:08.680 --> 00:21:15.400 It's not that difficult. Let's say the signal we receive is negative 65 dB. Let's roll back. 00:21:15.400 --> 00:21:22.520 Negative 65 dB. That's where they should be. Negative 65 dB. Oh my gosh, they're on the upper 00:21:22.520 --> 00:21:29.480 range of good. Very good here. Ooh, good. Excellent. So we're good, right? Well, no. 00:21:30.200 --> 00:21:35.240 We have to subtract out the noise. Well, now the noise is negative 90. 00:21:38.600 --> 00:21:43.400 So this is the received signal strength indicator, the RSSI. Remember, non-standardized. 00:21:44.040 --> 00:21:53.080 Negative 65. And then we need to subtract out what? The noise floor. So let's do this calculation. 00:21:53.080 --> 00:22:01.000 RSSI minus noise. Remember, these are both in decibel milliwatts. So we go negative 65 00:22:01.000 --> 00:22:08.360 minus a negative 90. Well, I got two negatives. That gives me a positive. Let's see. That would 00:22:08.360 --> 00:22:19.960 be 25. I'm getting a received signal strength of 25. That's what I'm receiving. Let's take a look 00:22:19.960 --> 00:22:28.680 at where that falls. If the SNR is in 25, let's look. Voice has a minimum of 25. I can barely 00:22:28.680 --> 00:22:37.080 use voice. That's the strength I'm at. Interesting. You see how we've changed where we were? 00:22:38.040 --> 00:22:45.480 If we roll back, we were initially... I'm rolling all the way back here. We were initially at the 00:22:45.480 --> 00:22:50.280 very high end here. We started at negative 65. Now, I understand we're changing charts, 00:22:50.280 --> 00:22:56.200 but it's important to understand the difference between RSI, received signal strength indicator, 00:22:56.200 --> 00:23:03.640 versus our initial signal strength. Remember, this is at the top of VOIP. I was at the top of VOIP, 00:23:03.640 --> 00:23:10.120 but there's so much noise there that I actually ended up dropping to the very bottom of VOIP, 00:23:10.120 --> 00:23:18.440 because when we look at this table for SNR, it says that once I take out my noise floor, 00:23:18.440 --> 00:23:26.600 if I'm at 25 received signal strength, that's not a good place for voice. I need to try and 00:23:26.600 --> 00:23:33.560 improve that. I'm at the very minimum. It's very important that you know that 25 and 20 00:23:33.560 --> 00:23:41.640 are very, very important numbers. One is the voice minimum, 25, and one is the data minimum, 00:23:41.640 --> 00:23:50.200 which is 20. In order to remember this, voice alphabetically comes after data. Look at the 25 00:23:50.200 --> 00:23:59.400 and 20. 25 comes after 20. That's how I remember it. So, data minimum is 20, voice is 25. Another 00:23:59.400 --> 00:24:06.200 way you can remember this is, remember our powers of three? Well, our powers of three said that 00:24:06.200 --> 00:24:12.760 every three decibels, I'm doubling the strength of the signal. This is five, so this is almost 00:24:13.720 --> 00:24:17.000 four times as powerful, or double and double again, two to the power of two. 00:24:18.120 --> 00:24:22.920 So, do I need a higher signal strength for voice? Yes, absolutely. So, that's another way you can 00:24:22.920 --> 00:24:28.280 remember it. You start at 20 with data, you need to up the signal strength to get to 25. 00:24:30.360 --> 00:24:39.800 Now, how do we take all this into account? What determines my noise? How does that 00:24:39.800 --> 00:24:47.960 come into play? Well, it really, really depends on what channels you use. Now, channels are very 00:24:47.960 --> 00:24:56.920 important in understanding that your traffic travels in a channel. Now, they say the 2.4 range. 00:24:57.000 --> 00:25:03.400 They say 2.4 gigahertz. Everybody's using 2.4 gigahertz. Now, is that strictly true? Absolutely 00:25:03.400 --> 00:25:09.240 not. If you take a look at this, you're actually using only a fraction of the channel. If we take 00:25:09.240 --> 00:25:16.440 a look at this channel here, we've got 1, 6, 11. These are common channels used in the 2.4 gigahertz 00:25:16.920 --> 00:25:27.640 range. And what this shows is we have a 22 megahertz channel width. So, if I take a look at 00:25:27.640 --> 00:25:39.800 2.4 to 2.42, it's actually 2.4 to 2, we would see that here to here is a channel. And if I take 22 00:25:40.360 --> 00:25:53.160 more, here to here is a channel. And here to here is a channel. Those are non-overlapping channels. 00:25:53.720 --> 00:26:00.040 Why? Well, let's take a look. Let me erase this. Let's dive a little deeper into this. 00:26:00.040 --> 00:26:04.040 If I have a channel, let's say I'm using channel 3, and I'll highlight this in red, 00:26:04.520 --> 00:26:10.760 pink. I'm using channel 3, and let's say a neighbor's using channel 1. Channel 3 is 00:26:10.760 --> 00:26:15.560 not a standard channel. I have an overlap here. You see this area here? 00:26:17.720 --> 00:26:24.920 This is an overlap in channels. What do I get if I'm using channel 1 and my neighbor is using 00:26:24.920 --> 00:26:31.960 channel 3? What I get is interference on anything that is transferred in this frequency range right 00:26:31.960 --> 00:26:44.360 here. That frequency range, probably 2.412 to 2.422. Any data that's actually being moved in 00:26:44.360 --> 00:26:51.720 that range, the signal loss is going to happen. Remember the RSSI we talked about? The signal 00:26:51.720 --> 00:27:01.080 to noise ratio? We've introduced now here in this channel, we just introduced interference 00:27:01.080 --> 00:27:05.800 because we're both using overlapping channels. That's why in the United States 00:27:05.800 --> 00:27:11.560 and in other places, we use non-overlapping channels. Channel 1, channel 6, and channel 11 00:27:11.560 --> 00:27:19.320 for 2.4. Now, other types of devices use other channels, so you've got to be careful on what's 00:27:19.320 --> 00:27:27.080 around you. Walkie-talkies, old cordless phones from when I was young use 2.4. There's lots of 00:27:27.080 --> 00:27:37.000 things that use radio waves, so you've got to be careful. Here, Japan and other places have 00:27:37.000 --> 00:27:43.320 opened up channel 14. In the U.S., this is not viable for the U.S. You cannot use this. The FCC 00:27:43.320 --> 00:27:48.440 will get mad, and they'll yell at you. There are emergency communication channels that communicate 00:27:48.440 --> 00:27:53.000 over that, and we do not want to create interference over those communication channels, 00:27:53.000 --> 00:27:57.960 so they cannot speak. But in other countries, it's okay because they don't use those channels 00:27:57.960 --> 00:28:04.360 for emergency communication. Does that mean we're off the hook when we use 5 gigahertz? 00:28:04.360 --> 00:28:10.040 Absolutely not. I want you to take a look at the 5 gigahertz range. Here, you can see we do have 00:28:10.040 --> 00:28:22.200 channels. It's 0.020 or 20 megahertz is the channel width. You can see that we have multiple channels 00:28:22.200 --> 00:28:30.200 here. What you'll notice, though, is we have many, many more channels. So this, in an office environment, 00:28:30.200 --> 00:28:36.840 will create much, much less interference because my neighbors could be using 100, and I could be using 00:28:36.840 --> 00:28:43.640 140, and they will never, ever interfere with each other. So that's why in office environments in the 00:28:43.640 --> 00:28:49.080 modern world, we often see people using the 5 gigahertz standard, and that is a more modern 00:28:49.160 --> 00:28:55.080 approach to wireless networking in an enterprise environment, is using the larger gigahertz. 00:28:56.120 --> 00:29:01.400 Now, 6 gigahertz does not need to be talked about in this course, but here, we'll talk about the 5 00:29:01.400 --> 00:29:08.920 gigahertz range. Now, there's something very interesting that happens from here to here. 00:29:09.880 --> 00:29:18.920 So, see 52, 56, 60, 64, 100, 104, 108, all the way to 140. Notice that there's a plus 4 here for every 00:29:18.920 --> 00:29:27.160 jump. Just be aware. I mean, that's not exam relevant, but you'll begin to see this more and 00:29:27.160 --> 00:29:34.200 more. It's plus 4. Let's take a look at what happens within that range. Remember I said that 00:29:34.600 --> 00:29:43.160 not everyone uses, not everyone, not every frequency is dedicated just to wireless? 00:29:43.720 --> 00:29:47.560 Well, here is something very important to understand in the 5 gigahertz range. 00:29:48.280 --> 00:29:56.840 Weather uses radar. Hospitals have different magnetic resonance machines and different types of 00:29:57.720 --> 00:30:06.600 things they radiate out. We got airplane radar. Well, those mostly fall in the Uni2 and Uni2 00:30:06.600 --> 00:30:15.160 Extended. If I roll back, Uni2 and Uni2 Extended. I marked those as important. Look at those channel 00:30:15.160 --> 00:30:23.160 numbers. Okay. If you are near an airport or a hospital, and I mean really near because 5 00:30:23.880 --> 00:30:29.480 gigahertz doesn't travel very far, but even if you're in a hospital, it's important to realize 00:30:29.480 --> 00:30:33.480 you may be creating interference. If you're in an airport with wireless, 00:30:33.480 --> 00:30:39.960 you may not want to use those channels. You may want to disable DFS, and those DFS rules only 00:30:39.960 --> 00:30:48.840 apply to the 5.2 to 5.7 gigahertz range. Just be very cognizant of using the 5 gigahertz range 00:30:48.840 --> 00:30:54.200 if you're in those industries. Hospital, weather, Doppler radar, news station, 00:30:54.200 --> 00:31:00.680 if you have Doppler radar, if it's on your roof, airplane, definitely pay attention to those. 00:31:03.000 --> 00:31:09.640 All right. That was it for that lesson. We will dive into antenna types in our next lesson, 00:31:09.640 --> 00:31:17.240 but in our last lesson, we talked about the medium of wireless, using the air to 00:31:17.240 --> 00:31:21.400 send out signals. Very important as a basic or basic understanding. 00:31:22.360 --> 00:31:30.040 We will dive into how antennas shape that in our next lesson. Thank you. Bye.