1 00:00:04,900 --> 00:00:10,540 Now for some of the wi fi explanations, I'm going to be using an analogue radio, old analogue radio. 2 00:00:10,540 --> 00:00:17,890 And you may be asking, David, I don't care about analog radios, but remember, wi fi is using wireless 3 00:00:17,890 --> 00:00:19,940 technologies just like this is. 4 00:00:19,960 --> 00:00:25,510 This uses different frequencies, but it's also using the air in a similar way to wi fi. 5 00:00:25,510 --> 00:00:32,320 And I'm going to be using this to demonstrate a concept which is Hertz or cycles per second. 6 00:00:32,470 --> 00:00:37,390 This has got kilohertz, megahertz, wi fi, we've got gigahertz. 7 00:00:37,390 --> 00:00:43,900 So it's well worth spending a little bit of time using an analog radio explained concepts such as channels 8 00:00:43,900 --> 00:00:51,100 or radio stations to use the analog radio station term or channels in wi fi, and also to explain frequencies 9 00:00:51,100 --> 00:00:57,580 which will help you understand why five gigahertz is better than 2.4 gigahertz, as in it's better at 10 00:00:57,580 --> 00:01:00,940 transmitting more data but does have other disadvantages. 11 00:01:03,330 --> 00:01:07,290 I've mentioned 2.4 gigahertz and five gigahertz frequencies quite a bit now. 12 00:01:07,290 --> 00:01:08,850 So let's explain what that is. 13 00:01:08,850 --> 00:01:13,260 And to help us with an analogy here, I've got an old style radio. 14 00:01:13,950 --> 00:01:15,450 On a radio like this. 15 00:01:15,450 --> 00:01:18,120 We will have different frequency ranges. 16 00:01:18,120 --> 00:01:23,580 Now, again, governments around the world dictate the frequencies and what they can be used for. 17 00:01:23,610 --> 00:01:25,800 So there's a frequency spectrum. 18 00:01:26,160 --> 00:01:29,790 Phones, as an example, have different radios inside of them. 19 00:01:29,790 --> 00:01:36,210 So I can connect to the cellular network, or I can connect to the wi fi network. 20 00:01:36,210 --> 00:01:40,860 So if you're in a plane as an example, you'll be told to turn off your cellular network. 21 00:01:41,220 --> 00:01:43,410 But you can use the wi fi connection. 22 00:01:43,680 --> 00:01:46,530 Different radios, different frequencies are used. 23 00:01:46,530 --> 00:01:50,340 Some frequencies will interfere with other devices. 24 00:01:50,340 --> 00:01:55,260 So as an example, some of the five gigahertz frequencies interfere with radar. 25 00:01:55,290 --> 00:02:00,270 So when you're near an airport, you have to turn off those frequencies you're not allowed to use in 26 00:02:00,270 --> 00:02:04,890 some countries, certain frequencies, such as five gigahertz, especially around airport. 27 00:02:05,700 --> 00:02:11,760 On a traditional radio like this or a radio in your car, you may have FM or AM. 28 00:02:11,760 --> 00:02:19,710 So different frequencies are used by FM or AM on a traditional radio, and this is obviously an old 29 00:02:19,710 --> 00:02:20,590 style radio. 30 00:02:20,610 --> 00:02:24,000 When I turn this on, I might hear nothing. 31 00:02:24,000 --> 00:02:32,090 So hopefully you can hear that all I hear is white noise because I'm not tuned in to a radio station. 32 00:02:32,100 --> 00:02:38,850 Now we talk about a radio station, but actually all a radio station is is me tuning the dial until 33 00:02:38,850 --> 00:02:42,420 I'm listening in on a specific frequency. 34 00:02:42,450 --> 00:02:46,210 Now, a lot of us will talk about a radio station rather than a specific frequency. 35 00:02:46,230 --> 00:02:53,400 Some radio stations, as an example, will say 94.2 FM is their radio station. 36 00:02:53,850 --> 00:03:00,180 If you or one, two, three something depending on where you are in the world, different radio stations 37 00:03:00,180 --> 00:03:06,800 will broadcast or transmit on a specific frequency, and you will get different radio stations depending 38 00:03:06,820 --> 00:03:07,380 where you are. 39 00:03:07,410 --> 00:03:12,450 You might have had this experience if you're driving long distance when you're driving and your radio 40 00:03:12,450 --> 00:03:19,540 set to a specific frequency or specific channel to use a wi fi term when you drive. 41 00:03:19,560 --> 00:03:25,950 At some point, the there's interference where you can hear two radio stations and then one will slowly 42 00:03:25,950 --> 00:03:27,750 get quieter and one will get louder. 43 00:03:27,750 --> 00:03:30,530 And then eventually you'll only hear the one radio station. 44 00:03:30,540 --> 00:03:37,080 So the idea there is think of this as two wi fi antennas, but this is in radio terms, we've got two 45 00:03:37,080 --> 00:03:43,230 antennas broadcasting and as you driving the signal from one gets weaker and weaker while the signal 46 00:03:43,230 --> 00:03:47,520 from the other gets stronger and stronger, and eventually you'll switch from one to the other. 47 00:03:48,360 --> 00:03:52,230 Your wi fi device, like your iPhone, will do something very similar. 48 00:03:52,230 --> 00:03:58,710 If it's moving through a enterprise network where they've got multiple antennas, it will associate 49 00:03:58,710 --> 00:04:01,160 to the one that's transmitting with the greatest power. 50 00:04:01,170 --> 00:04:04,890 And as you move away from that one, it will hear another one. 51 00:04:04,890 --> 00:04:11,850 And then what it'll do as you're moving is it will switch to another access point that's broadcasting 52 00:04:11,970 --> 00:04:13,980 the same SSID. 53 00:04:14,040 --> 00:04:18,260 It's this ID is a identifier for a wireless network. 54 00:04:18,269 --> 00:04:23,070 You've probably seen it many, many times on your wi fi device on this phone. 55 00:04:23,070 --> 00:04:30,620 As an example, if I go to wi fi connections, I can see different SSIDs or service set identifiers. 56 00:04:30,630 --> 00:04:37,320 These identify different wi fi networks that I can connect to and I can jump from one wi fi network 57 00:04:37,320 --> 00:04:38,070 to another. 58 00:04:38,070 --> 00:04:42,120 In this example, ABC one has been designated as five gigahertz. 59 00:04:42,120 --> 00:04:47,610 Just to make it easy for me to know that that's a five gigahertz network, but I could select ABC one. 60 00:04:47,850 --> 00:04:49,440 This is one of my wi fi networks. 61 00:04:49,440 --> 00:04:54,870 I know that that's a 2.4 gigahertz SSID or network that I'm connecting to. 62 00:04:54,960 --> 00:05:01,660 So service said identifiers or SSIDs allow us to know the name of a wi fi network. 63 00:05:01,680 --> 00:05:08,550 An iPhone moving around will try and associate with an access point or a device that's broadcasting 64 00:05:08,550 --> 00:05:10,110 with the most power. 65 00:05:10,110 --> 00:05:16,320 And then as that gets quieter, it will associate automatically with another access point that's broadcasting 66 00:05:16,320 --> 00:05:17,520 the same SSID. 67 00:05:18,090 --> 00:05:21,390 This radio supports frequency modulation or FM. 68 00:05:21,390 --> 00:05:24,990 We've got medium wave and we've got long wave on this radio. 69 00:05:24,990 --> 00:05:27,960 And what you'll notice is the frequencies differ. 70 00:05:27,960 --> 00:05:39,210 So for FM we've got 88 to 108 megahertz medium wave, we've got 540 to 1600 and long wave, we've got 71 00:05:39,210 --> 00:05:41,160 152 to 80 kilohertz. 72 00:05:41,160 --> 00:05:46,380 And I'll explain kilohertz, megahertz gigahertz in a moment. 73 00:05:46,410 --> 00:05:52,770 But the point is, is that different frequencies are used in the air for transmitting different signals. 74 00:05:52,770 --> 00:06:02,280 But within this range of frequencies, I can tune my radio to a specific radio station on that frequency 75 00:06:02,820 --> 00:06:04,920 when it's not tuned to a radio station. 76 00:06:04,920 --> 00:06:08,490 All I hear is white noise, something like this. 77 00:06:09,210 --> 00:06:18,300 But as I tune the dial on the radio, I'll hear a radio station take me to a different place. 78 00:06:20,330 --> 00:06:20,780 Just a. 79 00:06:26,830 --> 00:06:32,660 I have to be careful because of copyright recording some of these channels or radio stations. 80 00:06:32,680 --> 00:06:40,540 Notice the term a radio station is actually just me tuning the radio to a specific channel or to a specific 81 00:06:40,540 --> 00:06:42,440 frequency within a range. 82 00:06:42,460 --> 00:06:49,690 So different radio stations broadcast on specific frequencies or specific channels to use a wi fi term. 83 00:06:49,690 --> 00:06:53,890 And then I tune or listen in on a specific radio station. 84 00:06:53,890 --> 00:07:00,090 So my radio is tuned to that specific frequency which allows me to listen to that radio station. 85 00:07:00,100 --> 00:07:02,560 Same concept exists in wi fi. 86 00:07:03,700 --> 00:07:06,040 WiFi uses different frequencies. 87 00:07:06,370 --> 00:07:12,430 The two main frequencies that you need to be concerned with are 2.4 gigahertz and five gigahertz. 88 00:07:12,460 --> 00:07:18,520 Notice this is gigahertz, not megahertz or kilohertz, different frequency range, because once again, 89 00:07:18,520 --> 00:07:22,360 governments decide which frequencies are allocated to which applications. 90 00:07:22,540 --> 00:07:27,370 So 2.4 gigahertz is actually this range of frequencies. 91 00:07:27,370 --> 00:07:35,050 But within that range, I would tune to a specific channel to listen in on a specific radio transmission 92 00:07:35,050 --> 00:07:39,220 or basically to be connected to a specific access point or specific device. 93 00:07:39,370 --> 00:07:41,250 Five gigahertz is in this range. 94 00:07:41,260 --> 00:07:44,620 It's broken up into these specific ranges. 95 00:07:44,890 --> 00:07:47,050 But, you know, PowerPoint slides are really boring. 96 00:07:47,050 --> 00:07:48,520 I don't like PowerPoint slides. 97 00:07:48,520 --> 00:07:50,740 I much prefer showing you stuff practically. 98 00:07:50,740 --> 00:07:55,060 So let's have a look at these frequencies practically before we get there. 99 00:07:55,150 --> 00:08:03,610 I just want to point out that notice in the 2.4 gigahertz range here, we've got specific channels, 100 00:08:03,610 --> 00:08:09,790 and the channels that we are most concerned with is channel one, six and 11. 101 00:08:10,240 --> 00:08:16,420 These two channels, one, six and 11 are the channels that you should be using so that you don't have 102 00:08:16,420 --> 00:08:22,150 overlapping transmissions with other devices in the same frequency range. 103 00:08:22,240 --> 00:08:29,110 When you send a transmission on this channel, it's actually bleeding in to the other frequencies. 104 00:08:29,110 --> 00:08:34,059 So it's not just here, it's bleeding across a certain range of frequencies. 105 00:08:34,059 --> 00:08:39,640 If someone else was transmitting on this channel, they would be bleeding into your channel. 106 00:08:39,640 --> 00:08:45,670 And and here we'd be over talking each other or talking across one another, reducing our transmission. 107 00:08:45,970 --> 00:08:53,020 So typically you want to use six, 11 and one so that there is a gap between your transmission so that 108 00:08:53,020 --> 00:08:55,060 you're not talking over one another. 109 00:08:55,300 --> 00:09:01,000 So once again, if I was using Channel one and you were using Channel two, we would be over talking 110 00:09:01,000 --> 00:09:03,220 each other and reducing our throughput.