In today's lecture, we are going to look into the different generations of wireless technologies, emerging applications, spectrum usage, and also we'll take and learn a typical cellular network. Let us start with answering few questions. What is wireless communication, why it is needed, and how it is done? This lecture on this course will be about answering these important questions on wireless communication. In layman terms, if I want to call, what is wireless communication? The method of transmitting information from one point to another without using any connection like wires or cable. Let us start by taking and look into wired as well as wireless altogether. If you look into the advantages of wired communication, the major thing is reliability, stability, visibility, speed, and very important, security. But if you talk about the disadvantage of wired communication, we have lack of mobility, installation, higher maintenance cost, and obviously, we have wires. Now if we look into the advantage of wireless communication. What do we have? Advantages; mobility, lower installation, and maintenance cost, and we don't require any wires now. But the disadvantages are reliability, stability, visibility, security is an important issue, and also the speed. We can see the advantages and disadvantages of wired and wireless communication are completely opposite to each other. Now let us look into wireless communication evolution over the last few decades. If we see in 1980, we started with 1G which was supporting a data rate of one to five Kbps. After a decade or so, we got a new technology called 2G, which was using GSM, TDMA. It was supporting a bite rate of 25 Kbps. Then after roughly one decade or so, we got 3G, and similarly, in every decade we got a new technology. Thanks to our communication industry experts. We got 4G in 2010 and 5G in 2020. If you see 1G, we were supporting a data rate of one to five Kbps, and with 5G, we're supporting a data rate more than one Gbps. That's huge step. Now, let us look into the applications. When we were moving from 1G to 5G, well, the application have changed. In 1G, it was only about voice, we can only call. There was no messaging service or Internet. But when we went to a 2G, we got a new application called SMS service, so in 2G we can call, there's a voice as well as messaging service. 3G we got Internet, we were able to use worldwide web Internet, and that was, I think, major change in the cellular market. Then we move from 3G to 4G. I would say there was not much in application added, but yeah, we were able to do high video streaming, also video calling, what not we do right now because if we see at the current time, 4G is used almost in the 95 to 99 percent of the world. Now currently, we are talking about 5G. If you see the 5G applications are not only about voice communication or video streaming, it is more about connecting any devices that is available all over the world to enhance the performance. With the help of 5G will have smart cities, smart grid, smart health sector, and everything else going to be smart. Now let us look into the spectrum usage. When we are saying we are using 1G or 2G, 3G, 4G, and now we are saying 5G and few of the research has already started on 6G, what is changing in terms of frequency, in terms of spectrum? In 1G or 2G, we're talking about very low-frequency range. But now when we are moving towards 3G, 4G, and 5G, we are moving towards ultra-high frequency or super high-frequency range. You can see we are moving towards higher and higher frequency bend, and when we're talking about 6G, they're all talking about terahertz frequencies, more towards super and extra high-frequency range. Why is the researchers so interested in moving towards higher and higher frequencies range? The main benefit is the bandwidth. The higher the frequency, the higher bandwidth you are having and therefore, which increases the overall throughput. Now let us take an example of a typical cellular network. To let us, we have a base station, and we have multiple users. These users in 5G can be anything like mobile, UAV, drones, IoT device, anything. Communication can happen between user and base station in two ways, either base station wants to transmit or user wants to transmit. When user is transmitting a signal towards a base station, we call it uplink transmission. Similarly, when a base station transmits a signal to user, we call it downlink transmission. This terminology we should remember because we'll be using throughout the course. Now, let us look into what is the coverage a base station can provide. For example, if base station is able to serve a particular area, we call it a cell. Now, oversimplified view tells us that a base station should be employed at the center of a cell, and a cell follows a hexagonal shape. But is it possible in reality? That we need to look. We know real world we have mountains, high-rise buildings, so it is very difficult to have good propagation path between a user and a base station in an isotopical manner. What exactly happens in reality, the base station are placed irregularly depending on good communication paths rather than distance. To this, we need to remember that cells are not always in hexagonal shape. They can be in very different way. If you can see in this example, it depends not only on the distance between the user and the base station, but it depends more on how this communication path is. Maybe we have a high-rise building in between or a mountain in between, although the distances left would the hard, is not that good. In that case, maybe the communication path between this and this may not be that good when compared to the communication path between this and this although the distance is huge. We've done different transmitting and receiving antenna dimensions, we have multiple technologies in wireless communication, starting from SISO, single-input single-output, towards SIMO, MISO, MIMO, and now in 5G, we're talking about 5G MASSIVE MIMO. 4G used to have MIMO. We used to have two to four number of transmitter antenna, and two to four number of roughly receiver antennas. When we're talking about massive MIMO 5G, we are talking about a number of antennas of the order of 64, 120, 200s, or even 512, when we're talking about millimeter wave frequency ranges. We can see the number of antennas average, and these antenna increase generally happens at the base station. In the user, we cannot have so many numbers of antennas because of space constraints. Now, also in the base on what kind of multiple access techniques we are using, there are different technologies starting from CDMA, code division multiple access, which was used in 3G, OFDM, orthogonal frequency division multiplexing, which is using 4G, as well as 5G. There's also something called non-orthogonal multiple access, which has its own advantages. Most of the IoT cases, it is somewhat using 5D, but in future it will be used a lot. In this lecture, we learned that the 1G supported only one to five Kbps data rate, whereas 5G can support higher than 1Gbps data rate. We saw that 5G aims to provide connectivity for any kind of devices and applications that may benefit from being connected. With 5G, we are moving towards very high frequency and extra high-frequency ranges. Finally, we saw that 5G is using MASSIVE MIMO at the base station, and OFDM for multi-carrier transmission.