1 00:00:04,970 --> 00:00:10,820 Now for some of the Wi-Fi explanations I'm going to be using an analogue radio old analogue radio and 2 00:00:10,820 --> 00:00:11,900 you may be asking David. 3 00:00:11,930 --> 00:00:13,710 I don't care about analog radios. 4 00:00:13,880 --> 00:00:20,050 But remember Wi-Fi is using wireless technologies just like this is. 5 00:00:20,180 --> 00:00:25,800 This uses different frequencies but it's also using the air in a similar way to Wi-Fi. 6 00:00:25,800 --> 00:00:32,670 And I'm going to be using this to demonstrate a concept which is Hertz cycles per second. 7 00:00:32,690 --> 00:00:36,160 This has got kilohertz megahertz Wi-Fi. 8 00:00:36,170 --> 00:00:37,550 We've got gigahertz. 9 00:00:37,550 --> 00:00:41,900 So it's well worth spending a little bit of time using an analogue radio. 10 00:00:41,900 --> 00:00:48,020 Explain concepts such as channels or radio stations to use the analogue radio station term or channels 11 00:00:48,020 --> 00:00:54,710 in Wi-Fi and also to explain frequencies which will help you understand why five gigahertz is better 12 00:00:54,710 --> 00:01:00,760 than 2.5 gigahertz as in it's better at transmitting more data but does have other disadvantages. 13 00:01:02,910 --> 00:01:07,300 Now I've mentioned 2.5 gigahertz and 5 gigahertz frequencies quite a bit now. 14 00:01:07,310 --> 00:01:08,870 So let's explain what that is. 15 00:01:09,080 --> 00:01:15,480 And to help us with an analogy here I've got an old style radio on a radio like this. 16 00:01:15,500 --> 00:01:18,190 We will have different frequency ranges. 17 00:01:18,280 --> 00:01:23,800 Now again governments around the world dictate the frequencies and what they can be used for. 18 00:01:23,810 --> 00:01:29,890 So there's a frequency spectrum phones as an example have different radios inside of them. 19 00:01:30,050 --> 00:01:36,020 So I can connect to the Salih network or I can connect to the Wi-Fi network. 20 00:01:36,440 --> 00:01:42,260 So if you're in a plane as an example you'll be told to turn off your cellular network but you can use 21 00:01:42,260 --> 00:01:48,800 the Wi-Fi connection different radios different frequencies are used some frequencies will interfere 22 00:01:48,980 --> 00:01:50,510 with other devices. 23 00:01:50,510 --> 00:01:55,460 So as an example some of the five gigahertz frequencies interfere with radar. 24 00:01:55,460 --> 00:02:00,470 So when you're near an airport you have to turn off those frequencies you're not allowed to use in some 25 00:02:00,470 --> 00:02:07,070 countries certain frequencies such as 5 gigahertz especially around airports on a traditional radio 26 00:02:07,070 --> 00:02:15,470 like this or a radio in your car you may have F.M. or am so different frequencies are used by F.M. or 27 00:02:15,470 --> 00:02:18,620 am on a traditional radio. 28 00:02:18,620 --> 00:02:20,660 And this is obviously an old style radio. 29 00:02:20,810 --> 00:02:23,830 When I turn this on I might hear nothing. 30 00:02:24,140 --> 00:02:32,290 So hopefully you can hear all I hear is white noise because I'm not tuned in to a radio station. 31 00:02:32,300 --> 00:02:39,110 Now we talk about a radio station but actually all a radio station is is me tuning the dial until I'm 32 00:02:39,170 --> 00:02:42,630 listening in on a specific frequency. 33 00:02:42,660 --> 00:02:46,370 Now a lot of us will talk about a radio station rather than a specific frequency. 34 00:02:46,400 --> 00:02:53,790 Some radio stations as an example will say ninety four point two F.M. is their radio station. 35 00:02:54,020 --> 00:03:01,100 If you or one 0 3 something depending on where you on the world different radio stations will broadcast 36 00:03:01,130 --> 00:03:07,530 or transmit on a specific frequency and you will get different radio stations depending where you are. 37 00:03:07,580 --> 00:03:12,050 You might have had this experience if you're driving long distance there when you're driving and your 38 00:03:12,050 --> 00:03:17,840 radio set to a specific frequency or specific channel to use a Wi-Fi term. 39 00:03:18,230 --> 00:03:25,100 When you drive at some point the There's interference where you can hear two radio stations and then 40 00:03:25,100 --> 00:03:29,900 one will slowly get quieter and one will get louder and then eventually you'll only hear the one radio 41 00:03:29,900 --> 00:03:30,760 station. 42 00:03:30,770 --> 00:03:36,580 So the idea there is think of this as two Wi-Fi antennas but this is in radio terms. 43 00:03:36,590 --> 00:03:42,740 We've got two antennas broadcasting and as you driving the signal from one gets weaker and weaker while 44 00:03:42,740 --> 00:03:45,350 the signal from the other gets stronger and stronger. 45 00:03:45,350 --> 00:03:51,350 And eventually you'll switch from one to the other your Wi-Fi device like your iPhone will do something 46 00:03:51,350 --> 00:03:57,590 very similar if it's moving through a enterprise network where they've got multiple antennas. 47 00:03:57,800 --> 00:04:01,270 It will associate to the one that's transmitting with the greatest power. 48 00:04:01,400 --> 00:04:05,090 And as you move away from that one it will hear another one. 49 00:04:05,090 --> 00:04:11,630 And then what it will do as you moving is it will switch to another access point that's broadcasting 50 00:04:12,170 --> 00:04:18,410 the same SS I.D. as this I.D. is a identifier for a wireless network. 51 00:04:18,410 --> 00:04:23,900 You've probably seen it many many times on your Wi-Fi device on this phone as an example. 52 00:04:23,900 --> 00:04:32,630 If I go to Wi-Fi connections I can see different SS I.D. or service set identifiers these identify different 53 00:04:32,630 --> 00:04:38,210 Wi-Fi networks that I can connect to and I can jump from one Wi-Fi network to another. 54 00:04:38,210 --> 00:04:43,970 In this example ABC 1 has been designated as 5 gigahertz just to make it easy for me to know that that's 55 00:04:43,970 --> 00:04:47,970 a five gigahertz network but I could select ABC one. 56 00:04:47,990 --> 00:04:49,450 This is one of my Wi-Fi networks. 57 00:04:49,460 --> 00:04:55,160 I know that that's a 2.5 gigahertz SS I.D. or network that I'm connecting to. 58 00:04:55,160 --> 00:05:02,780 So service set identifiers or SS I.D. allow us to know the name of a Wi-Fi network an iPhone moving 59 00:05:02,780 --> 00:05:03,430 around. 60 00:05:03,560 --> 00:05:10,050 We'll try and associate with an access point or a device that's broadcasting with the most power. 61 00:05:10,340 --> 00:05:16,340 And then as that gets quieter it will associate automatically with another access point that's broadcasting 62 00:05:16,340 --> 00:05:17,810 the same SSD. 63 00:05:18,240 --> 00:05:21,450 This radio supports frequency modulation or F.M.. 64 00:05:21,470 --> 00:05:25,080 We've got medium wave and we've got long wave on this radio. 65 00:05:25,130 --> 00:05:28,120 And what you'll notice is the frequencies differ. 66 00:05:28,160 --> 00:05:39,200 So for F.M. we've got 88 to 1 0 8 megahertz medium way we've got 540 to 1600 and long wave we've got 67 00:05:39,260 --> 00:05:41,200 150 to two 80 kilohertz. 68 00:05:41,210 --> 00:05:46,610 And I'll explain kilohertz megahertz gigahertz in a moment. 69 00:05:46,610 --> 00:05:52,810 But the point is is that different frequencies are used in the air for transmitting different signals. 70 00:05:52,910 --> 00:06:02,120 But within this range of frequencies I can tune my radio to specific radio station on that frequency 71 00:06:03,020 --> 00:06:04,930 when it's not tuned to a radio station. 72 00:06:04,940 --> 00:06:09,350 All I hear is white noise something like this. 73 00:06:09,350 --> 00:06:23,160 But as I tune the dial on the radio I'll hear a radio station. 74 00:06:26,980 --> 00:06:29,470 I have to be careful because of copyright recording. 75 00:06:29,590 --> 00:06:37,180 Some of these channels or radio stations notice the term a radio station is actually just me tuning 76 00:06:37,180 --> 00:06:42,580 the radio to a specific channel or to a specific frequency within a range. 77 00:06:42,680 --> 00:06:49,960 So different radio stations broadcast on specific frequencies or specific channels to use a Wi-Fi term. 78 00:06:49,960 --> 00:06:53,920 And then I tune or listen in on a specific radio station. 79 00:06:53,920 --> 00:07:00,250 So my is tuned to that specific frequency which allows me to listen to that radio station. 80 00:07:00,250 --> 00:07:06,460 Same concept exists in Wi-Fi Wi-Fi uses different frequencies. 81 00:07:06,500 --> 00:07:12,580 The two main frequencies that you need to be concerned with are 2.5 gigahertz and 5 gigahertz. 82 00:07:12,590 --> 00:07:19,070 Notice this is gigahertz not megahertz or kilohertz different frequency range because once again governments 83 00:07:19,070 --> 00:07:22,710 decide which frequencies are allocated to which applications. 84 00:07:22,760 --> 00:07:30,770 So 2.5 gigahertz is actually this range of frequencies but within that range I would tune to a specific 85 00:07:30,890 --> 00:07:37,790 channel to listen in on a specific radio transmission or basically to be connected to a specific access 86 00:07:37,790 --> 00:07:41,310 point or specific device five gigahertz is in this range. 87 00:07:41,390 --> 00:07:47,150 It's broken up into these specific ranges but you know PowerPoint slides are really boring. 88 00:07:47,150 --> 00:07:48,530 I don't like PowerPoint slides. 89 00:07:48,530 --> 00:07:54,200 I much prefer showing you stuff practically so let's have a look at these frequencies practically before 90 00:07:54,200 --> 00:07:55,290 we get there. 91 00:07:55,370 --> 00:08:04,130 I just want to point out that notice in the 2.5 gigahertz range here we've got specific channels and 92 00:08:04,460 --> 00:08:13,880 the channels that we are most concerned with is Channel 1 6 and 11 these two channels 1 6 and 11 are 93 00:08:13,880 --> 00:08:19,940 the channels that you should be using so that you don't have overlapping transmissions with other devices 94 00:08:20,480 --> 00:08:21,940 in the same frequency range. 95 00:08:22,430 --> 00:08:29,420 When you send a transmission on this channel it's actually bleeding in to the other frequencies so it's 96 00:08:29,420 --> 00:08:34,240 not just here it's bleeding across a certain range of frequencies. 97 00:08:34,280 --> 00:08:40,640 If someone asks was transmitting on this channel they would be bleeding into your channel and and here 98 00:08:40,640 --> 00:08:46,160 would be over talking each other or talking across one another reducing our transmission. 99 00:08:46,160 --> 00:08:52,850 So typically you want to use six eleven and one so that there is a gap between your transmission so 100 00:08:52,850 --> 00:08:55,450 that you're not talking over one another. 101 00:08:55,460 --> 00:09:01,490 So once again if I was using Channel 1 and you were using Channel 2 we would be over talking each other 102 00:09:01,820 --> 00:09:03,080 and reducing our throughput.