Cisco CCNA 200-301 – Wireless Networking Fundamentals Part 3

6. Wireless Channels and Radio Frequencies

In this lecture you’ll learn about RF, that’s radio frequencies and channels. WiFi services operate in the two 4 frequency spectrum that’s allocated for ism industrial, scientific and medical use. You’ll see more about what that means in a second. Because of this, a radio operator’s license is not required wired and ism industrial, scientific and medical use. Devices do not have regulatory protection against interference from other users of the band. So let’s see what this means. So I will open up a chart here. This is the radio frequency allocations in the US. So this is controlled by the government. And here you can see all of the frequencies that are assigned to the different types of radio communication. For example, you can see that for FM broadcasting for radio, that is 88 to 108. You can also see maritime communications in here, fixed satellite, et cetera.

And right in the middle here you see industrial, scientific and medical. So it’s the industrial, scientific and medical that is used for the WiFi communications. But there’s loads of other types of communications happening over the airwaves as well. So taking the FM broadcasting as an example, if you wanted to set up a radio station in your area, well, you can’t do that and then just start broadcasting on a particular frequency in this range. It’s regulated by the government. So you would have to apply for a license to do that. And one of the things that the local authorities will do is they’ll check that nobody else is using that frequency. Because if you think about, for example, my local radio station back home, they broadcast on 96. 9. If somebody else started broadcasting on 96. 9, then those two signals would interfere with each other. You would be hearing both stations at the same time. And of course, if you’re hearing both at the same time, then neither one of them is going to make sense.

So that’s why there is the regulatory compliance in all of these other bands to make sure that people are not stepping on each other’s toes. But for WiFi networks, well, everybody’s got a WiFi network at home. It wouldn’t be practical for everybody to have to apply to their local authority to use a particular frequency in their home. So because of that, really it’s unregulated and anybody can use any frequency that they want as long as it is in these industrial, scientific and medical ranges. So it’s not regulated, which means it’s easy to get set up, but it does mean that there’s a pretty high chance that we’re going to get interference. So let’s talk about that more as we go through the lecture. So I’ll go back to the slides again. Before we talk about the radio frequencies more, let’s talk about the standards and how they have evolved over time. So the standard for WiFi communications is IEEE 800 and 211 that first came out in 1997 and operated in the 2.

4 GHz frequency range and the maximum bandwidth was two megabits per second. So it was pretty slow. So not long after that, in 1999, 8211 A and 8211 B both came out. 8211 B also operates at 2. 4 is 5. Maximum bandwidth with eleven B is eleven megabits per second. For 8211 A it was 54 megabits per second. So that did give a pretty good speed increase. Then in 2003, 8211 G came out. That also operates at 2. 4. Because it’s operating at 2. 4 GHz, this can be backwards compatible with 800 and 211 B, which is also 2. 4 is 5 GHz. So A and G are not compatible with each other. Now, with the backwards compatibility, maybe you had a wireless device which only supported 800 and 211 B, did not support 800 and 211 G. Well, in that case, if you had some devices on your network which did support 800 and 211 G, then they could operate at up to 54 megabits per second.

The old devices which only supported eleven B, they could operate up to eleven megabits per second. In 2009, 8211 N came out, and it’s capable of operating at both 2. 4 and 5 GHz. Big speed improvement there, up to 600 megabits per second. And because it supports 2. 4 and 5 GHz, it’s backwards compatible with A, B and G. Again, if you’ve got older wireless clients which only supported A, B or G, they would only get the speed that was supported there. But if you did have a wireless client that supported 800 and 211 N, up to 600 megabits per second there.

And finally, in 2013, 8211 AC came out. It’s at 5 GHz, it sports up to 3500 megabits per second, and it is backwards compatible with A and N. Because it’s 5 GHz, it’s not compatible with the older 2. 4 GHz only Standards cisco access points support all standards. If you’ve got a Cisco AP, it’s not like you have to pick and choose just one of these. You can have multiple different options here, all enabled on the AP at the same time. Okay, so let’s look at the 2. 4 GHz spectrum and the 2. 4 GHz spectrum. It’s a spectrum. It is a range of frequencies. It’s not just exactly 2. 4 GHz, it actually ranges from 2. 4 to 2. 4835 GHz or 2. 4 to 2. 497 in Japan.

And that spectrum, so that frequency range is divided up into smaller 22 MHz ranges of frequencies, which are called channels. So a channel is just a range of frequencies that can be used for your WiFi. Each access point operates in one channel. And as you can see in the diagram here, some channels overlap and can cause interference with each other. Just like if we had two radio stations which were playing out music at the same frequency, they are going to be on top of each other. It’s causing interference. So you can see here, that channel one is shown in blue. It goes from there to there, and then channel two goes from here.

So there’s a lot of overlap between channel one and channel two. Also channel three is overlapping there as well, and you can see it’s all the way until we get up to channel six, where it is not overlapping with channel one. So in the 2. 4 GHz spectrum in the US, there’s actually only three channels which do not overlap with each other. Those are one, six and eleven. So if you’ve got neighboring APS, you want to use non overlapping channels to make sure that they don’t overlap with each other. Okay, looking next at the 5 GHz spectrum, 2. 4 GHz channels are 22 MHz wide. 5 GHz channels are 20 MHz wide, and they have less overlap than the 2. 4 GHz channels. So it’s not such a problem here. Neighboring AP should still be separated by at least one channel though, to reduce the chance of interference. With the 5 GHz spectrum, channels can be bonded.

So with single channel, it is 20 MHz wide. You can bond two together to make it 40 MHz wide. You can bond four together to get 80, and you can bond eight together to get 160. And that multiplies the data rates by two, four or eight, depending on whether you’re going for 80 or 160. So let’s have a look at that. So you can see the 5 GHz spectrum here are all the different channels up here at the top. So if we’re just using the single channels, we’re not bonding at 20 MHz. You can see we’ve got channels 36, 44 and so on. We could bond channels 36 and 40 together, that would double it to 40. That’s going to give us more bandwidth, more throughput there.

We could double that again at 80 MHz, that would be channels 36 to 48. Or we could go up to 168, which would be 36 all the way up here. Okay, so that was the 5 GHz spectrum. Now I have been talking in this lecture about the interference. I mentioned about how the Ism band is unlicensed. So you do not have any guarantee that the frequency belongs to just you. Natural fact, it’s unlikely that that is going to be the case. And many devices can cause interference in the 2. 4 GHz spectrum, such as microwave ovens and wireless video cameras, fluorescent lights and baby monitors. Comparing 2. 4 and 5 has got greater range. It goes further, it’s also got better propagation, meaning it gets through obstacles better as well. But the 2. 4 GHz range is more crowded, there’s more things, there more chance of having interference. 5 AC has higher throughput than is available with any of the 2. 4 GHz options. So you might think, well then for sure I’m going to be using 8211 AC. But your client stations might not be compatible with it yet. They might only be compatible with 2.

4 GHz, which would force you to use that or to upgrade them. Because of all the potential for interference. Site surveys should be carried out for WiFi networks. The purpose is to find the best placement of access points for maximum coverage of the required area and minimum leakage outside it. You want wireless to be available everywhere you want it inside the building. You don’t want it going outside the building because that would be a security concern. The site survey is also going to discover potential sources of interference as well. So the way that you do this is you use some software on your laptop, you can walk around the building and this software, it’s going to detect any potential sources of interference. It can also help you with the AP placement as well. And a wireless LAN controller can manage a channel allocation and a power level of the APS to get the best wireless quality.

And let’s have a look at an example of using some software on my laptop which can give me information about the different wireless frequencies in my area here around about my house. So I have got some free software called Insider open here. I’ve just opened it and you can see it is monitoring the wireless frequencies right around my laptop here.

And you can see that I’ve got home WiFi available. That’s my home wireless network here and that is supporting 800 and 211 AC. So it’s great. It’s the latest standard and you can see it’s available on both 2. 4 roundabout me. Nobody else is operating at 5 GHz, so that’s great. I should get really good quality there. But if I connected my laptop at 2. 4 GHz, you can see there’s all these other wireless networks round about me as well. And you can see that the channels are all overlapping down here. So to minimize the interference when I’m connected over wireless, I’m using the 5 GHz range. Okay, that was everything I wanted to show you here. See you in the next.

7. Wireless Security

In this lecture you’ll learn about RF, that’s radio frequencies and channels. WiFi services operate in the two 4 frequency spectrum that’s allocated for ism industrial, scientific and medical use. You’ll see more about what that means in a second. Because of this, a radio operator’s license is not required wired and ism industrial, scientific and medical use. Devices do not have regulatory protection against interference from other users of the band. So let’s see what this means. So I will open up a chart here. This is the radio frequency allocations in the US. So this is controlled by the government. And here you can see all of the frequencies that are assigned to the different types of radio communication. For example, you can see that for FM broadcasting for radio, that is 88 to 108. You can also see maritime communications in here, fixed satellite, et cetera.

And right in the middle here you see industrial, scientific and medical. So it’s the industrial, scientific and medical that is used for the WiFi communications. But there’s loads of other types of communications happening over the airwaves as well. So taking the FM broadcasting as an example, if you wanted to set up a radio station in your area, well, you can’t do that and then just start broadcasting on a particular frequency in this range. It’s regulated by the government. So you would have to apply for a license to do that. And one of the things that the local authorities will do is they’ll check that nobody else is using that frequency. Because if you think about, for example, my local radio station back home, they broadcast on 96. 9. If somebody else started broadcasting on 96.

9, then those two signals would interfere with each other. You would be hearing both stations at the same time. And of course, if you’re hearing both at the same time, then neither one of them is going to make sense. So that’s why there is the regulatory compliance in all of these other bands to make sure that people are not stepping on each other’s toes. But for WiFi networks, well, everybody’s got a WiFi network at home. It wouldn’t be practical for everybody to have to apply to their local authority to use a particular frequency in their home. So because of that, really it’s unregulated and anybody can use any frequency that they want as long as it is in these industrial, scientific and medical ranges. So it’s not regulated, which means it’s easy to get set up, but it does mean that there’s a pretty high chance that we’re going to get interference. So let’s talk about that more as we go through the lecture.

So I’ll go back to the slides again. Before we talk about the radio frequencies more, let’s talk about the standards and how they have evolved over time. So the standard for WiFi communications is IEEE 800 and 211 that first came out in 1997 and operated in the 2. 4 GHz frequency range and the maximum bandwidth was two megabits per second. So it was pretty slow. So not long after that, in 1999, 8211 A and 8211 B both came out. 8211 B also operates at 2. 4 is 5. Maximum bandwidth with eleven B is eleven megabits per second. For 8211 A it was 54 megabits per second. So that did give a pretty good speed increase. Then in 2003, 8211 G came out. That also operates at 2. 4. Because it’s operating at 2. 4 GHz, this can be backwards compatible with 800 and 211 B, which is also 2. 4 is 5 GHz. So A and G are not compatible with each other. Now, with the backwards compatibility, maybe you had a wireless device which only supported 800 and 211 B, did not support 800 and 211 G.

Well, in that case, if you had some devices on your network which did support 800 and 211 G, then they could operate at up to 54 megabits per second. The old devices which only supported eleven B, they could operate up to eleven megabits per second. In 2009, 8211 N came out, and it’s capable of operating at both 2. 4 and 5 GHz. Big speed improvement there, up to 600 megabits per second. And because it supports 2. 4 and 5 GHz, it’s backwards compatible with A, B and G. Again, if you’ve got older wireless clients which only supported A, B or G, they would only get the speed that was supported there.

But if you did have a wireless client that supported 800 and 211 N, up to 600 megabits per second there. And finally, in 2013, 8211 AC came out. It’s at 5 GHz, it sports up to 3500 megabits per second, and it is backwards compatible with A and N. Because it’s 5 GHz, it’s not compatible with the older 2. 4 GHz only Standards cisco access points support all standards. If you’ve got a Cisco AP, it’s not like you have to pick and choose just one of these. You can have multiple different options here, all enabled on the AP at the same time. Okay, so let’s look at the 2. 4 GHz spectrum and the 2. 4 GHz spectrum. It’s a spectrum. It is a range of frequencies. It’s not just exactly 2. 4 GHz, it actually ranges from 2. 4 to 2. 4835 GHz or 2. 4 to 2. 497 in Japan.

And that spectrum, so that frequency range is divided up into smaller 22 MHz ranges of frequencies, which are called channels. So a channel is just a range of frequencies that can be used for your WiFi. Each access point operates in one channel. And as you can see in the diagram here, some channels overlap and can cause interference with each other. Just like if we had two radio stations which were playing out music at the same frequency, they are going to be on top of each other. It’s causing interference. So you can see here, that channel one is shown in blue. It goes from there to there, and then channel two goes from here.

So there’s a lot of overlap between channel one and channel two. Also channel three is overlapping there as well, and you can see it’s all the way until we get up to channel six, where it is not overlapping with channel one. So in the 2. 4 GHz spectrum in the US, there’s actually only three channels which do not overlap with each other. Those are one, six and eleven. So if you’ve got neighboring APS, you want to use non overlapping channels to make sure that they don’t overlap with each other. Okay, looking next at the 5 GHz spectrum, 2. 4 GHz channels are 22 MHz wide. 5 GHz channels are 20 MHz wide, and they have less overlap than the 2. 4 GHz channels. So it’s not such a problem here.

Neighboring AP should still be separated by at least one channel though, to reduce the chance of interference. With the 5 GHz spectrum, channels can be bonded. So with single channel, it is 20 MHz wide. You can bond two together to make it 40 MHz wide. You can bond four together to get 80, and you can bond eight together to get 160. And that multiplies the data rates by two, four or eight, depending on whether you’re going for 80 or 160. So let’s have a look at that. So you can see the 5 GHz spectrum here are all the different channels up here at the top. So if we’re just using the single channels, we’re not bonding at 20 MHz. You can see we’ve got channels 36, 44 and so on. We could bond channels 36 and 40 together, that would double it to 40. That’s going to give us more bandwidth, more throughput there. We could double that again at 80 MHz, that would be channels 36 to 48. Or we could go up to 168, which would be 36 all the way up here. Okay, so that was the 5 GHz spectrum. Now I have been talking in this lecture about the interference.

I mentioned about how the Ism band is unlicensed. So you do not have any guarantee that the frequency belongs to just you. Natural fact, it’s unlikely that that is going to be the case. And many devices can cause interference in the 2. 4 GHz spectrum, such as microwave ovens and wireless video cameras, fluorescent lights and baby monitors. Comparing 2. 4 and 5 has got greater range. It goes further, it’s also got better propagation, meaning it gets through obstacles better as well. But the 2. 4 GHz range is more crowded, there’s more things, there more chance of having interference. 5 AC has higher throughput than is available with any of the 2. 4 GHz options.

So you might think, well then for sure I’m going to be using 8211 AC. But your client stations might not be compatible with it yet. They might only be compatible with 2. 4 GHz, which would force you to use that or to upgrade them. Because of all the potential for interference. Site surveys should be carried out for WiFi networks. The purpose is to find the best placement of access points for maximum coverage of the required area and minimum leakage outside it. You want wireless to be available everywhere you want it inside the building. You don’t want it going outside the building because that would be a security concern. The site survey is also going to discover potential sources of interference as well.

So the way that you do this is you use some software on your laptop, you can walk around the building and this software, it’s going to detect any potential sources of interference. It can also help you with the AP placement as well. And a wireless LAN controller can manage a channel allocation and a power level of the APS to get the best wireless quality. And let’s have a look at an example of using some software on my laptop which can give me information about the different wireless frequencies in my area here around about my house.

So I have got some free software called Insider open here. I’ve just opened it and you can see it is monitoring the wireless frequencies right around my laptop here. And you can see that I’ve got home WiFi available. That’s my home wireless network here and that is supporting 800 and 211 AC. So it’s great. It’s the latest standard and you can see it’s available on both 2. 4 roundabout me. Nobody else is operating at 5 GHz, so that’s great. I should get really good quality there. But if I connected my laptop at 2. 4 GHz, you can see there’s all these other wireless networks round about me as well. And you can see that the channels are all overlapping down here. So to minimize the interference when I’m connected over wireless, I’m using the 5 GHz range. Okay, that was everything I wanted to show you here. See you in the next.

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