From the course: CompTIA A+ Core 1 (220-1201) Cert Prep

Wi-Fi standards

From the course: CompTIA A+ Core 1 (220-1201) Cert Prep

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Wi-Fi standards

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- 802.11 is a very old standard, but just because it's old, that does not mean we are not constantly updating it to get it faster and support more systems and do better all the time. Now, the original 802.11 standard actually defined a networking speed of about 1 megabit per second. Nobody ever saw that one and that's okay. So what we've seen over the years are what we call extensions to the standard. They have names like 802.11a, or 802.11g, or 802.11ac. So it's still the 802.11 standard, but they extend the standard to support newer technologies, faster speeds, able to support more systems, that type of thing. Now, the A+ exam is going to really hit you hard on making sure that you know all of the 802.11 extensions, so let's get them covered right here. Now, before we get into the individual extensions, let's get one thing clarified. The beautiful part of 802.11 is that it's based on the unlicensed industrial, scientific, and medical bands, ISM bands. Now, there's a lot of ISM bands, but these are going to use one or two or both of two different bands. Number one is going to be the 2.4 gigahertz band, and number two is going to be the 5 gigahertz band. So let's talk about what does band mean for a minute, okay? Now I'm not talking about a band with horns and drums, I'm talking about a band being a range of radio frequencies. So if we're going to have a range of radio frequencies, well, that's important. We could do this entire thing on just one exact frequency, but the idea is that lots of people are going to want to use 802.11. There's going to be wireless access points all over the place. And if we just have one frequency, your plumber and the hairdresser upstairs and Bob next door, we're all going to stomp on each other, and it's not going to work. So that's why we use the concept of a band. Now, the 2.4 gigahertz band runs from about 2.412 gigahertz up to about 2.84 gigahertz. So we've got this whole range of frequencies to work with. So different wireless access points can use different ranges so we don't stomp on each other. Well, now we got a problem. The idea behind 802.11, it's supposed to be fairly user-friendly. So, unless we want you to go into your wireless access point and everybody has to tune to 2.438. Now, nobody wants to do that, okay? So what they did instead is they made pre-made channels. So, in the 802.11 2.4 gigahertz band, there are really 14 different channels, and each channel takes a different piece of this band. And the idea is, is that you can tune your wireless access point to use one channel, while your plumber uses a different channel, and Bob next door uses a different channel, and we don't stomp on each other, is the whole idea behind this. Now, there are officially 14 channels, but only if you're in Japan. Japan is a very crowded place so they need lots of channels. If you're in Europe, you get up to 13 channels. And here in the United States, you only get up to 11, which is actually plenty for the stuff that we do. On the 5 gigahertz band, now that's going to run from 5.15 gigahertz to about 5.875 gigahertz. And the channels are a lot more complicated here. In this case, we have channel numbers that start with like the number around 36 up to about 64, and it doesn't actually even span out very well. The other challenges is that there aren't any odd numbered channels, they just skip a lot of channel numbers. This is their choice because they're inventing these standards. And then it even continues up to around 100 to up to about channel 165. So if you look at the entire 5 gigahertz band, you've got a whole bunch of channels in there, we've skipped a lot of numbers, but the nice part is, is that it's a very, very powerful band and we can really dial it down very, very nicely. Okay, now that we understand that there's two different bands and each of these bands use channels, let's go ahead and talk about the different extensions. The first one is going to be 802.11a. 802.11a was one of the earliest extensions to 802.11. It ran at a blistering 54 megabits per second, which was pretty fast in those days, and it ran on the 5 gigahertz range. Second, and it came out really about the same time that 802.11a did, was 802.11b. 802.11b ran at 11 megabits per second, which back then sounded like, wow, crazy fast. And it ran on the 2.4 gigahertz band. Now, they came up with another standard, and probably the one that really put 802.11 on the map, and that was 802.11g. 802.11g took all the goodness of 802.11a and 802.11b and put it into one standard. So 802.11g ran at 54 megabits per second, and it ran on the 2.4 gigahertz band. Now, I want you to think about this for a minute. If I've got a wireless access point that is running 802.11g, that means it's running on the 2.4 gigahertz band. That means I am backwardly compatible with 802.11b. Inside a wireless access point is a radio, and this radio is either a 2.4 gigahertz radio or a 5 gigahertz radio. Backward compatibility is a big deal. So if you've got 802.11g, you are automatically backward compatible with 802.11b. However, you are absolutely not backwardly compatible with 802.11a because you don't have a 5 gigahertz radio in there. Got the idea? Okay. Next is 802.11n. 802.11n was a very interesting standard. First of all, it actually ran on both bands. So 802.11n ran both on the 2.4 gigahertz as well as the 5 gigahertz. The nice part about 802.11n wireless access points is they were backwardly compatible with any wireless NIC out there. You had an old 802.11b? It ran on your 802.11n. You have an old 802.11g? It runs on your 802.11n. 802.11a? Runs on your 802.11n. So, in that aspect, it was pretty nice. The other thing that 802.11n introduced is something called MIMO. MIMO is kind of an interesting thing. What it does is that it allows a single wireless access point to use multiple antennas to change its radiation signal in such a way that it almost kind of zeroes in on a device. So if you have a wireless device that doesn't move a lot, MIMO can be a really powerful feature. And there's nothing to configure, you just make sure you have an 802.11n wireless NIC and you have an 802.11n wireless access point, and you get the chocolatey goodness of MIMO. The next step and the one that we're enjoying these days is 802.11ac. 802.11ac is incredibly fast. Not only does it split the channels up, but it improves the concept of MIMO that we saw in 802.11n and creates what's known as multi-user MIMO or MU-MIMO, where instead of just having one client that we can kind of zoom in at a time, it can zoom in on multiple clients at a time, simply depending on the number of radios it has put in it. So it's absolutely fascinating. The other thing about 802.11ac that is important is that a lot of 802.11ac WAPs will have a 2.4 gigahertz radio in there that is just for backward compatibility. It has absolutely nothing to do with the ac standard itself. So people get a little confused. Now, us nerds, we love talking about like 802.11a and g and ac and that stuff because, well, we're cool, but the Wi-Fi Alliance, the people who make this stuff, decided not that long ago to come up with another terminology. So what they'll do is they'll call it Wi-Fi 4, for example, for 802.11n, and Wi-Fi 5 for 802.11ac. I think the reason they're doing that is because if you go out and buy an 802.11ac wireless access point, you're not going to get the benefits of 802.11ac until you get 802.11ac-capable wireless NICs. You've got a laptop and it's only 802.11n? You're not going to get 802.11ac until you replace the wireless NIC, if you even can. If you've got a smartphone and it only does 802.11n, you're not going to get 802.11ac. It's just not in there, you're going to have to buy new smartphone. Now, the other thing is, is that for a lot of other devices, particularly desktops, most of the time, you can do upgrades or at least snap in a new card to take advantage of these different powers. So, be careful with your different extensions to 802.11 and make sure that your NIC matches your WAP. - CompTIA has added the 6 gigahertz band to the A+ Core 1 exam, which has been around for a few years now. The 6 gigahertz band was introduced in the 802.11ax to be supported along with 2.4 and the 5 gigahertz band. The 6 gigahertz band is also part of the Wi-Fi 6E and Wi-Fi 7 standards for routers and other enabled devices. Here is both a comparison and a summary of the Wi-Fi bands you will see on the A+ exam. 2.4 gigahertz provides a longer range, but has slower data transfer speeds. 5 gigahertz has less range than 2.4 gigahertz, but has faster data transfer speeds. 6 gigahertz offers the least coverage, but the data transfer speeds are super fast.

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