In this lecture module, we will focus on Wi-Fi and Bluetooth. First of all, this is because Wi-Fi and Bluetooth are the most widely used IoT networking techniques. This is because they are on all smartphones. In addition, they are so widely spread in ways that they are being used by smartwatches and smart devices in all types that naturally, they become the priority application, networking techniques to support various IoT services. Because they are such widespread and so important, we will take closer looks into them in this module. First, we'll start with Wi-Fi. A Wireless Local Area Network is a technology that is going to connect devices within a local range on approximately 30 meters, using some type of a wireless distribution system. Among that, the applications that can be supported are home, school, computer laboratory, building office, practically everything. The wireless LAN market consist of various components and the major companies are like Cisco, HPE, Huawei, Ubiquiti and other major networking vendors. In 2016, the overall market size for wireless LAN and Wi-Fi devices reached $9.38 billion, and you can see why I am focusing on this in a separate lecture module. Overall, based on the Q1 of 2017, the enterprise wireless LAN vendor market revenues. Looking at the proportion, you can see the distribution of the major vendors and how they are occupying the overall total sales. With special notice is the number one company, Cisco. Cisco systems has a lot of networking technologies especially when it comes to routers, and switches, and various IP-based services. They are one of the leading vendors in the world. Naturally, because of that, they have a true advantage in the wireless LAN, the Wi-Fi market as well. That is why Cisco, here, has an overall of $537.39 million earning in the scale of this, and the overall occupation of holding of the overall market is in the 43.4 percent range. This is truly significant and you see the other companies as HP, Aruba, Ubiquity and other companies as well over there. But one thing that is worth some extra notice is who's growing the fastest. One example is like Huawei. This company has shown very fast and large scale increments in their overall market share. Where they increased by 229.7 percent over one year, and that's noticeable. They are claiming overall 3.7 percent of the market share and this is based upon the 2017 Q1 statistics. Wi-Fi, use with a hyphen or not. You will see both forms in literature and documents. Just notice that they are the same. This is a representative wireless LAN technology that uses the ISM radio band. The ISM stands for industrial, scientific, and medical, and we've already studied this in a separate lecture in the former module. The ranges of frequency that we're interested in are the 2.4 gigahertz, the UHF, Ultra High Frequency range and the 5 gigahertz range which is SHF, Super High Frequency range. These are ISM bands that our global bands and worldwide ISM bands which make them most attractive, but on the other hand, because their worldwide and they have very good signal characteristics and bandwidth characteristics to support data rates of various rates, even including high data rates, naturally, their occupancy is high which means that there are many devices that are competing for access which means that there could be a lot of interference. Wi-Fi transmission. The 5 gigahertz range, which is a higher frequency range, this enables higher data rates more throughput. The 2.4 gigahertz range, this year has slightly lesser data rate support but on the other hand, it has increased coverage. This is because this frequency range, the signals, penetrate through solid objects very well. So, the shadowing based overall performance degradation is very little which makes it very attractive for wireless local area networks. Beamforming and other multiple antenna technologies like MIMO or MIMO, multiple input, multiple output. Meaning that at the transmitter, there are multiple antennas, at the receiver, there are multiple antennas and you use them together to send at higher data rates. This MIMO or MIMO, technology is used to increase the data rate and quality of service, QoS. We have access points and these play critical roles in our wireless local area networks. This is a device that allows Wi-Fi devices to connect to a wired network. These devices that we're talking about as Wi-Fi devices are smart phones, smartwatch, various smart devices, laptops, tablet computers, so many. The access points, APs are usually connected to a Internet gateway which have router capabilities inside or the access point itself has a built-in small router that supports this, and this is a very common thing. Looking at the network infra, it looks like this. The access point is connected to the Internet and various devices that exists within its range will use Wi-Fi to connect to the access point. Now, once they get to the access point, they can communicate with each other within this Local Area Network or they can connect with somebody else that's connected to the other side of the Internet. There is representatively two modes, and one is infrastructure mode and the other is Ad-Hoc mode, but I'll start with this because mostly we are using this. The infrastructure mode is a mode in which the access point, AP helps the Wi-Fi devices to communicate with each other and communicate with a wired network which is connected to the Internet. The typical network structure is called a BSS, Basic Service Set, and this is where one access point will service multiple Wi-Fi devices and it will connect them to the wired Internet, and that is what we call BSS, Basic Service Set, and this is a typical infrastructure mode in which we have PCs, a laptop, a tablet PC, and there could be of course smart phones. They are connected to an access point over there and the access point is connected to a switch which is connected to a router, a gateway that is connecting you to the Internet. Then there's Ad-Hoc mode which is, this is the other mode from the infrastructure mode. A Wi-Fi device or station will communicate directly with each other, without the help of an access point and you will use this when there is no access point or when you just want to skip it even though there may be one, I will not use the access point. I will have my device communicates with the other device directly. This is also called peer-to-peer mode. The Ad-Hoc mode may show up as peer-to-peer or for short P2P, with a two in the middle. The service set structure of the network is called an Independent Basic Service Set, and ad-hoc mode, this will support the IBSS mode. The network structure will look like this. Where devices will directly connect with each other and in this wireless local area network, you do not see an access point. That is connected to the wired Internet. Looking at this for BSS and and ESS. The BSS is the Basic Service Set which is the basic building block of a wireless LAN based upon 802.11. In Infrastructure Mode, a BSS is formed by the access point and WiFi stations STAs. Now, the AP or access point, acts as a master and controls all stations within the BSS. The extended service set the ESS, this is a set of two or more BSSs that are connected to a single network and it extends the range of the Wi-Fi station in its overall mobility. ESS example would be something like this. Where, you have a land router that is connected to two access points and each access point is servicing their BSS. They are connected to the land router, to the internet and this forms the ESS, and of course, this is just a simple example where there could be more BSSs that are supported here and in this example I only drew two, because of the size of this screen. These are the references that I used and I recommend them to you. Thank you.
