So WiFi is officially called IEEE 802.11 and that's a technical attribute standard. And if you look there, you will see the specifications for WiFi. So the 802 part is for Local Area Networks or LANs and LANs can either be wireless, like in this case or they can also be wire line. Like in the case of an Ethernet local area network. You may have heard of Ethernet before if you have an Ethernet can able /g, if you're not connecting via WiFi to your internet right now, then you're, might be connecting directly with an Ethernet cable. And the .11 part is for wireless. So 802, as we said, is for local area networks, and then .11 specifies that it's a wireless Local area network. But nobody really wants to look around say IEEE 802.11 so people just coined the better term WiFi which stands for Wireless Fidelity. So, for a while up until around 1999 there were no real standards. Even on WiFi, or nobody was, people would walk around and say that their devices were WiFi that didn't necessarily conform to the WiFi standards. So in 1999, the WiFi alliance was set up to ensure interoperability, and we looked at the word in the last section when we talked about Europe and adopting GSM as the global standard for over in Europe for cellular networks. in this case, we mean interoperability among devices for WiFi. And so if they stamp this symbol on your device, it means that it conforms the WiFi standard, or a specific WiFi standard. And what do we mean by specific WiFi standard? Well, there's more than just 802.11 we actually cook some of an alphabet soup if you want to look at it that way.They're a lot of different standards and you may have heard of some of these before: there's 802.11B, 802.11A, 802.11G, 802.11N. And these are just four of them, right so WiFi started maybe around 1997 when it was officially called WiFi. and it came around in a frequency band of 2.4 GHz at first and supported a maximum speed of 2 Mbps. You can see over the years, the maximum speed has improved, and so let's stop there for a second and let's say, what do you mean by speed, well We measure speed in what's called a megabit per second.So, what does that exactly mean? Well, when we talk about speed, when you're driving your car, you say, miles per hour, kilometers per hour, meters per second, or however you say it. What you're saying there, you're saying that you go a certain distance in a certain amount of time or on average, that's kind of how you're driving right now. And when we measure speed in a network, we measure the number of bits that we're sending per second. So your device will transmit at a certain number of bits per second, and we talked about how a bit, in the last lecture, is either a zero or a one, just a logical zero or one. Like in computer code and so when we talk about bits per second or bps for short, we're saying the number of bits that are going over the network in one second and that's on average. So you're sending a number of bits over the network and then in one second you're just basically probing and saying, well, how many bits are going to pass through here in one second on average? And we measure in mega bits per second, because its many, many and many its per second. Because bit is small little piece and we transmit millions of them in each second and gigabits per second and now what we can handle, and so we set mega bits per second with in millions and just like when we say megahertz we meant millions of hertz, and, and so on. And so, then in 1999 we went to 802.11b and that was the first official [UNKNOWN] standard still at 2.4 gigahertz and went up to 11 megabits per second. And so, these are mostly in alphabetical order, there's a little variation there, for the most part it is, but here's one example. b came out and then actually a came out with an even higher data rate of 54 Mbps at a different frequency range, in the same year, so they found out they could transmit much, much higher in that frequency range, and then g came out in 2003. And that was still at 54, but it was down then at the 2.4 GHz range and then as of 2009, we have 802.11n, which is the most commonly used right now, and that's in both 2.4 and around 5 GHz range, and that supports up to a maximum speed of 100 Mbps. And, clearly that will vary, as we will see, so you're not always going to get 100 Mbps, it'll depend on who else is on the network, and so on. And so, as the data rates improved over the years, the number of devices that wanted to access WiFi went way up. So back in 2009, when IEEE 802.11n came out so 802.11n came out, we had somewhere around 600 million devices, and then by 2015, it's projected that that's going to go up to 2.2 billion. So as the data rates go up, there's more and more of a demand. We saw a very similar trend with cellular networks.
