Hi, it's very nice to meet you. I am Kwang Soon Kim, Professor in Yonsei University. Recently, in every day of my life, I use my smart phone for downloading today's hot popular songs and listening to them. Enjoying fun videos and getting information from the web pages around the world. How about you? I think you do the same. Such a life is common nowadays and everyone takes it for granted. But if you are a curious person, which I'm sure because you are watching this lecture, you may have some questions. How and in what principle such things can be realized? Many of such questions can be answered if you understand the principles of information theory and wireless communication theory. Through this and the following six lectures I will raise five fundamental questions about them. Stay with me during this lecture then, you will get the answers. In our life we always get information from what we sense. For example, to see this picture delivers the visual information of a beautiful scenery to us. Nowadays every information including video and audio is stored and delivered in a digital format by using zero and one. Then, how can we convert what we see in a digital format? For this the first fundamental question is, how can we represent information into a binary format? And you will get the answers and they include the definition and essence of information, how to quantify the amount of information, and the tradeoff between information rate and quality. And nowadays, such digital information is everywhere. In live cameras, storages and servers that are far apart from my smartphone. However, we can easily access them every time, everywhere. That means such a large amount of digital information is transferred fast and reliably, even without wire connection. Then, naturally arising second fundamental question is, how can information be transferred? And you will get the answers and they include, what delivers the information, how many amount of information can be delivered, and what are the required resources. This picture shows some circuits in iPhone 6. Among many chips the indicated chip is for information transfer and is called MODEM chip. A modem chip is able to convert digital information into the corresponding radio wave and vice versa, so that the principles and theory for information transfer is commercially realized. Then naturally arising fundamental question is, how does it realize the information transporting theory and principles? And you will get the answers, and that includes how a modem is composed and what is the role of each part. And how they are combined to realize the theory. Now, consider a practically environment that you'll use your smartphone. A typical service provider covers a nationwide area and accommodates a lot of users. And you want to use your smartphone while you are moving by walking or even in a bus. Also, multiple rays are mixed due to many obstacles. In this case, the received signal quality becomes unpredictable and time varying. So in a practical environment, each user experiences a fluctuation in the reception of the signal quality that it is hard to be predicted at the transmitter. And this makes it hard to deliver information reliably. Then a naturally written question is, how can high-rate data be delivered reliably in practical cellular environments? And they will get the answers and they include, how we can connect a number of users in a large area efficiently. And, how high rate data can be delivered reliably in practical environments. A teaser for the last question is to use a cellular structure by dividing a large area into cells and employing a base station for each cell. However, there are still many number of users in each cell. Such many users in a cell want to simultaneously access to the base station and the base station needs to support them. Then, the final arising fundamental question is how can many users access simultaneously? And you will get the answers. And they include, what are popular multiple access schemes, how they allocate resource for channelization, and how their rate tradeoff among users look like. In the following five lectures, you will get all of the answers, one by one. See you again, and stay with me.
