Welcome. My name is Tyler McMinn with Aruba, a Hewlett Packard Enterprise company, and this is the Aruba mobility essentials video series. We're in part 1 on the fourth video, and this is covering data modulation, where in the previous video we covered the different wireless LAN organizations that govern the standards that all these technology uses, now we're going to dive a little deeper into the technology itself, and how radio is actually propagated through modulation. Stay with me, it's going to be a fun one. Data modulation, what is it? Where do we use it? Why do we have it? Well, let's start with the basics. When you're trying to send data from your mobile device or from your laptop to an access point, that data is crossing the airwaves as a radio wave, if you will, so all the packets of information and frames of data, those are going to be transmitted essentially as ones and zeros. This is sent in such a way that we want to overcome some of the issues that we have in wireless such as collisions, interference, absorption, free space path loss. Any of these issues that make our signal not-so-great, wireless needs to buffer and overcome that, in a way that when you're talking about a cable from a switch to a device, that's not as big of a deal. The cable protects the signal in transmission, whereas with wireless, this information is just out there, in a world of contention, between you and the access point. Other devices, walls, people with their, what is it, 68 percent water consistency in their bodies causing absorption and other radio waves. All of that stuff can make for a very bad experience if we're not careful. One of the nice things about this though, is that while on wired, everything's sent across on wires, and we just send our representations ones and zeros on wireless, the transmission of data itself can adjust and compensate dynamically for whatever environment that you're in, to the extent that you can at least hear the other side. Once you go beyond the range of the AP, well, then you're not hearing anything. But as long as you can hear it, we can slow the modulation or change the modulation to a slower rate and overcome some of those issues. Wireless we transmit using these radio waves. I know I draw this as a particle and I'll continue to do that but in reality, what it is, is a wave that's expanding from the point of origin, the antenna, and goes out until it's received by a device, and then I guess it collapses on itself and becomes a particle. I don't know, that's above my pay grade. But the access point can change its radio properties to represent what a one and zero is. As opposed to just sending a different voltage on a cable, like you see here, what your access point is doing is, it's negotiating a block of information that's going to ultimately be interpreted as a one or as a zero. If we lose a little bit of that because of the modulation and the encoding that we're using, we can actually compensate for that loss, and still end up with what we want. This is what a wave looks like. You've got an antenna that's going to be the source of the transmission. Typically a series of antennas using conjunction or a single antenna, it doesn't really matter, your radio wave will then come off of this using electrical signals. The wavelength is the distance between the peaks of these radio waves, and the amplitude is the overall strength of the signal. The higher the amplitude, the bigger the wave, the more power that's been put into that signal. You use the common example of someone is throwing a rock into a pond, or a pool, or something like that, and it hits the water, and immediately you see these waves jetting out from that point of impact, where there are very strong and high at the point the rock hits. But then as you get further and further away to the edge of the pond, the waves have died down. How's that possible if it's water? What's going on? Well, the energy of the rock is displacing the water as it expands out, it dissipates that energy. However, even if you're at the edge of the pond or right where the rock hit, the actual frequency that you see these crests, these peaks is going to be the same. The frequency is a measurement of the number of waves per second that's splashing against the shore of that pond. With our radios broadcasting at 2.4 gigahertz or in the five gigahertz range, that hertz is one sign or one rotation of this wave. It's one instance of it, and every time you do that, that's one hertz, this is a second hertz, this is a third hertz. That is the hertz measurement per second. So one second, one wave would be one hertz, 1,000 waves or hertz would be one kilohertz of information. If you get into megahertz, and then finally gigahertz, you're talking billions of waves per second. Five gigahertz would be five billion per second there. The phase is the relationship of the wave, and if that phase shifts or change, it's a very dramatic change, which means it's very easy to interpret that change even at greater distances, where your signal may not be the best. There are many ways that an access point in a radio will manipulate those factors to indicate a one, or a zero. This is known as Data modulation. You are modulating the radio signal in such a way, some ways are subtle, some are more pronounced. The more changes that you can implement, the more information you can articulate across here. Some examples of this would be like, modulation manipulating waves. If you use amplitude, and change the height of the wave to be higher or a little bit lower, and then maybe higher again, that could indicate a change in zeros, or ones through the use of amplitude-shift keying, and you're basically keying in information, based on shifts and amplitude. Frequency, is where you're suddenly changing the frequency, in order to indicate information. A common one that we started with was phaseshift keying, where you're changing the direction of the sign, to indicate a change in zeros or ones as you're sending your information. Some modulation methods can carry more data than others, indicating faster data rates, because they're utilizing all of these, or most of these in different ways. Initially, like with the 802.11 early days, we only used binary phase shift keying. To bump up our speeds, we implemented quadratic phase shift keying, which gave us speeds from binary of one and two megabits per second. With quadratic phaseshift keying, we could bump that number up to 5.5 and even 11 megabits per second. We could effectively double the data rate, because we were using instead of 180-degree shifts in our phaseshift keying, where we would shift the frequency, like turn it like a knob. It started a 180 degrees upside down. With quadratic, you shift it just 90 degrees and started there. Every time you shift 90 degrees in whatever direction, that would indicate four different possibilities, whereas 180 degrees only indicates two possibilities. Effectively two to four, you're doubling the amount of data. That same concept, you could expand it into quadratic amplitude modulation, where we could take blocks of changes, and be able to push much bigger amounts of data in conjunction with frequency, and phase shift key changes. This sounds fairly complicated, it's really not meant to be. It's good to know that, this is essentially how a one or zero is effectively being represented. In this case, if you want to check out this website that's posted here, this is just a real simple website, that is available to show you a radio wave as time goes on, and you can see these frequencies here. You can increase the frequency, or you could decrease the frequency, there's a little slider right here. You can increase the amplitude, amplitude being the strength of the signal. You can see the waves get bigger. That allows us to go through walls and other sources of absorption, that once you go through those walls, we were coming off of a wall here, you would see it be much smaller, even though there's no change in frequency, the change in the strength of the signal deteriorates. A weaker signal opens you up to issues with interference, other sources of absorption, or just simply free space, path loss where you just so far away from the AP, the signal dies out amongst the background noise. A stronger signal, or being closer to the original signal strengthens. It gives you a stronger amplitude. The stronger the amplitude, the more likely that you're going to get a clear signal. If you have a clearer signal, you can generally leverage some of these higher, or faster modulation methods that are available. Some of these modulation methods are only available in some of the higher throughput standards like 802.11N, AC, and the newest one, AX, whereas some of these earlier ones, were only really available with 802.11B, and G. The standards, as time goes on, and the standards improve, they open themselves up for faster data modulation rates, that can be negotiated between, your access point in your station. The good news is, other than positioning your access point, and where your clients are going to be, where your AP is compared to where your laptop is. Of course, you can pick your 802.11N, standard that you want to use. Beyond that, that's pretty much it. All of this negotiation occurs below the hood, so that we're not really tweaking our frequency shifting or amplitude shifting, or phase shifting, this is all part of the standard itself. What the access point and the station will negotiate, is whether they're going to utilize any of these modulation techniques, and how they get utilized in their Modulation method. What modulation they ultimately settle on, and that can change from second to second. Should interference show up, or should the station start to drift further away from the access point, someone walks the laptop further away, or into another room, or someone stands between you and the laptop. The laptop and the access point will constantly negotiate in real-time, which modulation they're going to use, maybe a faster one, because the signal is so good, or maybe they'll go with a slower one, but it's more robust and gives you the optimum amount of throughput. I hope that wasn't too crazy. There's a lot of math that I skipped over here. There's a lot more where they dive into the indifferent encoding methods and all that. It's absolutely fascinating. For our purposes, data modulation, it's just that automatic negotiation between your access point in your stations there, your client machines. I hope this was an interesting dive into the technology. We're going to end the video here. In the next video, we'll go on to look at antennas. Hope this was interesting for you, I'll see you guys in the next video. Thank you.