If you spend a long enough time designing it and you can produce enough of them, you can do extraordinarily complex things very, very cheaply. Use OCW to guide your own life-long learning, or to teach others. So we're dealing with an unsoluble problem here. In digital systems, performance is precisely specified as Probability of Error, P e. In digital systems, P e determined by modulation scheme and Signal to Noise Ratio, SNR. Wave form goes through here, noise gets added, the modulator, the text, those binary digits, comes out with some approximation to these three zeros. Download files for later. The word complex is an extraordinarily complex word. So I can split up the pie in any way I want to, and we'll talk about that a lot as we go on. P e= number of errors in n bits n 17 Flynn/Katz - SDR July 1, 2010 Something that most teachers don't understand. This is a good case study of why the information theoretic approach works and why theory works. The fact that you have a 1 in here is a little bit strange, and we'll find out where that comes from. Topics in Mech. But I had no idea that it was ever going to be important. There are more than 350+ Video Courses, more than 12000 video lectures across 10 subjects. Unit I : INTRODUCTION TO WIRELESS COMMUNICATION SYSTEM Types of Wireless communication : Click Mobile System Around the World: Click Evolution of mobile: Click 1G 2G 3G 4G mobile communication: Click WLL, WLAN and Unit 1 University Question paper discussion: Click Bluetooth and Unit II Syllabus discussion and How mobile phone works ? It's the same idea. How many such binary sequences are there? Learning communication from scratch would be a herculean task, if you are not clear about what all you would want to hear. I have to send this in a certain bandwidth. It's actually the second caveat, too. Most people who have complicated devices, whether they're audio devices or what have you, are using less than one percent of the fancy features in them. It would be nice if I could send it at optical speeds. There was a time in the early '70s when all the theoreticians who worked in communication theory all were going around with long faces saying everything that we can do has been done, the field is dead, nothing more to do, might as well give up and go into another field. If you have a certain amount of power that you're willing to transmit and a certain amount of noise, and the number of bits per second you can transmit is going up with w. But look at this affect with p here, the effect with p is logarithmic, which says as I increase this parameter m and I put more and more bits into one symbol, this quantity is going up exponentially, which means the logarithm of this is going up just linearly with m. This gives you, if you look at it carefully, the same trade-off as the simple-minded example I was talking about. So by increasing m, I can decrease the bandwidth, by increasing m, I can reduce the bandwidth, but by reducing the bandwidth, the power is going up. Well, you see the hitch when you program a computer, namely, if you look at word processing languages, yes, they become bigger and bigger every year, they become more and more complex, they will do more and more things. It means the problem of interpreting the bits, the problem of going from something which you view as having intelligence down to a sequence of bits is the problem of the source coder. Register As Student. 6.451, which is the companion course which follows after this uses it as a prerequisite. The other part of this is that all of this breaks down in the same way. So the source encoder has to understand the source. Low cost with high complexity requires large volume. What the channel accepts is either of these binary streams or packets, but then queueing exists. So you find the system which has no constraints in it, and it evolves with all of these things changing at the same time. Unlike a traditional book, this text contains the theory of both analog and digital communication systems supported by simulations (MATLAB & Mathcad) and video lectures referenced throughout the chapters. Lecture 01: Introduction to Communication Systems Outline This lecture introduces the basics of communications systems, including • The basic architecture of a communication system • Source-channel separation 1 Prelude Communication is the task of delivering a piece of information from a source to a destination. If you know something about practical engineering systems for communication, you know that there's an organization in the U.S. called the FCC, and every other country has its companion set of initials, which says what part of the radio spectrum you can use and what part of the radio spectrum you can't use. We will understand what that distinction is as we go on. So it's important. We work on them because we want to understand some aspect of the real problem. Call us at 8287971571 or fill the form below. As another example of my own life, for a long time I thought -- this is rather embarrassing to say -- but I was a theoretician and not much of an engineer for a very long time. The reason for all these equations that we have, it's not a way to understand reality. Important systems are not designed by the kinds of things you do in homework exercises. In analog systems, performance is subjective. Signal Propagation and Path Loss Models. The fundamental problem of the channel is very, very simple. So there's that point at which the light goes off in your head at which it becomes simple. This came whole cloth out of this one mind. In other words, if what you're dealing with is the kind of situation where you're an amateur photographer, you go around taking all sorts of pictures, and then you encode these pictures -- what do I mean by encoding the pictures? This course will provide an introduction and history of cellular communication systems that have changed our lives during the recent four decades and will become an essential and inseparable part of human life. Register As Teacher. He took up cryptography because it happened to use all the ideas that he was really interested in. Send to friends and colleagues. Then you go down to this point. 1.2 megabits if you're a medium technology person, or several gigabits if you're one of these persons who likes to gobble up huge amounts of stuff. If you have enough lead time they become cheap. Test Series Mentorship. There are things where there just isn't any structure. Books & E-Books. Like a difference between one signal and the next signal. You move around to different times, it's still there. It's the way the different pieces fit together. There's no signup, and no start or end dates. I want to talk a little bit right at the end, I'm almost finished, about computational complexity in these communication systems that we're trying to worry about. It doesn't take a lot of imagination to say if you have a detector here and there's this symbol that comes through here, noise gets added to it, you're trying to decode this symbol, and there's this Gaussian noise, which is just sort of spread around, it's concentrated. If the two come together, the whole thing works. Find materials for this course in the pages linked along the left. NPTEL Video Lectures, IIT Video Lectures Online, NPTEL Youtube Lectures, Free Video Lectures, NPTEL Online Courses, Youtube IIT Videos NPTEL Courses. That's what happens when you try to turn things into binary digits. What's important is you start to understand what assumptions in the problem lead to what conclusions. What is important is not the complexity of the individual messages, it's the probabilistic structure that tells you what are the different possibilities. Has length 100, the first bit can be 1 or zero, second bit can be 1 or zero -- that's four combinations. I sort of put these on one slide but I couldn't. Third bit can be 1 or zero also -- that makes eight combinations of three bits. You can look ahead at them, if you would like to, before Monday. P.S. You have to look at what parts of it are important, what parts of it aren't important, and the only way you can do that is having a catalog of the simple-minded things in the back of your mind. You can do everything more cheaply now than you could before. Finally, when you get to the input wave forms and output wave forms, you've solved both of these problems and you can then focus on what's important here. Subject: Communication Systems 2 SMART Subject Teacher: Dr. Abdul Sattar Saand Objectives of the Course-Synopsis This course introduces students Communication Systems This course will give you a comprehensive overview of a wide range of communications systems and networks, including voice, data, video, and multimedia. And ask those questions. A sequence of m binary digits, there are 2 to the m combinations of this. What Shannon's results says is that no matter what you do, no matter how clever you are with this noise that exists everywhere, the fastest you can transmit with the most sophisticated coding schemes you can think of is this rate right here, which is what you would think it might be just from the scaling in terms of w and m, where when you increase m the power goes up exponentially. That's the first caveat. Now, I split them up into different wave forms, which I send at spaced times. » Finally, we have symbols here going into a discrete encoder. Now, you look at this noise and you say I have to keep some separation between these numbers. There's a whole range of graduations. Electrical Engineering and Computer Science. I could take each sequence of eight bits, turn them into 1 of 256 wave forms, transmit one wave form, then a little bit later transmit another wave form and so forth. PROFESSOR: Somehow I have to keep these things seperate. Zoom is the leader in modern enterprise video communications, with an easy, reliable cloud platform for video and audio conferencing, chat, and webinars across mobile, desktop, and room systems. These things work and they can be understood because they're very highly structured. » As I always like to say, noise is like death and taxes, you can't avoid them, they're there, and there's nothing you can do about them. You take all of those and after you have all of these in your mind, you then start to study the real engineering problem and you say I put together this and this and this and this and this -- this is important, this is not so important, here, this is more important. Whenever you start dealing with this problem of source encoding, you also need to worry a little bit about the packet structure. Knowledge is your reward. Fundamentally, how much does it cost to build the system? 2, 2 lecture hours) But you still don't understand it the first time through. He was working on other things, which were, in fact, very important things, and he was doing those things for the government. So that's the story. Here's a picture which shows it better than the words do. You can find the course notes at EET Online Courses Notes and/or UNSW Online Courses. When I find the measure of distance for wave forms, what do I want to make it responsive to? The answer is totally irrelevant to everything. This was not a mistake many, many years ago, but it is a mistake now, because communication theory at its core is information theory. Which says that this layering of communication system that we're talking about really ultimately makes sense. NPTEL Video Lectures, IIT Video Lectures Online, NPTEL Youtube Lectures, Free Video Lectures, NPTEL Online Courses, Youtube IIT Videos NPTEL Courses. We have an input which is now a wave form. That's what digital communication is. The source encoder has to know a great deal about what that input is. With more than 2,400 courses available, OCW is delivering on the promise of open sharing of knowledge. The course serves as an introduction to the theory and practice behind many of today's communications systems. I can send m binary digits in this bandwidth, w. Therefore, I can send bits at a certain rate. They told me I should go into vacuum tubes, which was the coming field at that time. It's partly what we were just starting to say over here. You deal with unit impulses all the time. People earlier had figured out they could do that with the sampling theorem, but the sampling theorem wasn't very practical, but Nyquist's way of doing it was practical. That's part of what we have to understand to understand why we're doing what we're doing. Example – Radiotelephony, broadcasting, point-to-point, mobile communications, computer communications, radar and satellite systems. Free Video Lectures from Top Colleges and Universities. Home So, with a separation between the numbers, say the separation is 1, let this define the number 1. ... Business Laws Ethics And Communication CAIOG1; Cost Accounting and Financial Management CAIOG1; Ethics and Communication CAIOG1; ... Video Lectures. But when you're all done, if you design an engineering system and you don't see in your mind why the whole thing works, you will wind up with something like Microsoft Word. Think about how you wo… You can see that as I change m, the power is going up exponentially with m. In other words, the trade-off between bandwidth and power is kind of nasty in this simple-minded picture. Electrical Engineering and Computer Science ... All the everyday communication systems that we deal with are incredibly complex in terms of the amount of hardware, the amount of software in them. So the three stages in that process are first go to sequences, go from sequences to symbols -- namely, you have a finite number of symbols, which are quantized versions of those analog numbers which can be anything. We'll find out that that works in general, so we will do most of that. Most source coding you start out with a wave form, such as with voice, or with pictures you start out with what's more complicated than a wave form, some kind of mapping from x-coordinate and y-coordinate and time, and you map all of those things into something. Topics covered: Introduction: A layered view of digital communication, Instructors: Prof. Robert Gallager, Prof. Lizhong Zheng. But in any situation we look at, the channel is fixed. The point is something becomes simple after you understand it. Yeah? He had these ideas turning around in his head for about eight years while the second World War was going on. As far as their function of word processing, some of us think there have been advances in the last 30 years. PROFESSOR: Because the analog gets represented in binary digits, because we have chosen essentially, because of having studied Shannon at some point, to turn all the analog sources into binary bit streams. 6.451 talks about all of those. Lecture 1 (01/07) pptx pdf. Looking back historically, every time the communication field has seemed dead, and I can think of three or four such times in history, those have been the exact times where it was great to get into the field. Electronics for Analog Signal Processing - II - Prof. K. Radhakrishna Rao 19. This course will provide an overview of current and future wireless systems, wireless channel models including path loss, shadowing, and statistical multipath channel models. Know a great deal about what you ought to know a great deal about what that distinction as... 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