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. We will talk a great deal about this. You can do this cheaply and the chips work faster and faster so you can do more and more complicated things very, very easily. Since the numbers are not exactly the same, we have to deal with questions of approximation. Basics of analog and digital video: color video formation and specification, analog TV system, video raster, digital video formats (Chap. You now see companies like Qualcomm that were started then, Motorola of whom major divisions were started back then. There are things where there just isn't any structure. Please review the probability that you are supposed to know because you will need it very shortly. EE1 and ISE1 Communications I Pier Luigi Dragotti Lecture five Lecture Aims • To introduction to communication theory (21) About Downloadmela is a educational download portal that provides interview questions,video lectures,question papers,aptitude,puzzles,reasoning,sample resumes,essays,presentations,projects,tutorials and cheat sheets. Namely, you look at the energy difference between these sequences. Sometimes there's a very difficult question about what you mean by something being simple. Most of us have become blinking 12's. 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. This is one of over 2,200 courses on OCW. Books & E-Books. Home Kind of an awkward thing because if I developed a receiver which didn't have any bandwidth constraint on it, and I looked at this noise coming in, which was spread out over all frequencies, the noise would burn out the receiver. Check my site on digital communications tutorials. 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. You quantize those numbers, that gives you a symbol sequence. This is something we haven't talked about yet. So the problem is the source encoder takes these bits, takes the source, whatever it is, with its meaning and everything else, turns it into a stream of bits -- you would like to turn it into as few bits as possible. When you talk about information theory, it's a total misnomer from the beginning. The fundamental problem of the channel is very, very simple. Freely browse and use OCW materials at your own pace. If I take a single bit that's either zero or 1, I map a zero into one wave form, I map a 1 into another wave form, I send either wave form a or wave form b. I somehow want to make those wave forms as different from each other as I can. 6.041 is a particularly good undergraduate course. This is sort of Moore's law. 6.450 forms the first of a two-course sequence on digital communication. Well that's why we have to study wave forms as much as we do in this course. Complex systems are often not well thought through. Communication Engineering. When you deal with source coding, you're talking fundamentally about the problem of taking whatever the source is, and it can be any sort of thing at all -- it can be voice, it can be text, it can be emails, the emails with viruses in it, whatever -- and the problem is you want to turn it into a bit stream. 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. So, in fact, you can separate these wave forms. So the source encoder has to understand the source. The other part of dealing with these channels is that suddenly we have to deal with 4AA analysis and all of these things, if you don't have some kind of subject in signals and systems. The channels that we're most interested in usually send wave forms. The other part of this is that all of this breaks down in the same way. ... 40 videos Advanced Control System Design for Aerospace Vehicles. Free video lectures are a good way to access high-quality education from your own home. I think it's probably taught here better than it's taught at most places. For this added of white Gaussian noise with a bandwidth constraint, Shannon showed that the capacity was w times log of 1 plus the power in the system times the noise power times w. Now, I don't expect you to understand this formula now, and there's a lot of very tricky and somewhat confusing things about it. This was not a mistake many, many years ago, but it is a mistake now, because communication theory at its core is information theory. I somehow have to worry about the fact that if I send them over a finite bandwidth, there is no way in hell that you can take finite bandwidth wave forms and send them in finite time. These numbers are supposed to resemble these numbers in some way or other. It's a fundamental part of every communication system. In other words, this white Gaussian noise has infinite power. One of the major keys to making these things simpler is to have standardized interfaces and to have layering. There are always nasties. What we're mostly interested in is how to reduce bit rate for sources. Knowledge is your reward. Namely, if I have some source and I'm trying to transmit it over some physical channel and I have two engineers -- one of them is a data compressor, and the other is a channel guy. Zoom Rooms is the original software-based conference room solution used around the world in board, conference, huddle, and training rooms, as well as executive offices and classrooms. You want to do run length coding, for example. What the channel guy is trying to do is to find a way of sending more bits over this channel than could be done before. This problem here combined with this problem deals with all of these many problems where what you're interested in is taking a sequence of numbers or a sequence of whatjamacallits and quantitizing them and then coding. Lectures . Every once in awhile because of the noise, one of these bits comes out wrong, and because they come out wrong this discrete decoder says ah-ha, I know that what was sent/put in was either zero, zero, zero or 1, 1, 1. So I'm going to try to explain to you why this is important, and something today about what the proper inter-relationship is of engineering and theory. In communications, a channel is the means of passing information from a sender to a recipient. The problem is we have so much complexity we don't know how to deal with it anymore. It's actually the second caveat, too. We start with a brief review of Fourier analysis and random processes. We call this digital communication, and what I've been telling you is that the sources that we're interested in are most often wave form sources. It queues up, it takes a long time to get it out of my computer and into this other person's computer. What does this have to do with the price of rice in China or with anything else? ... Business Laws Ethics And Communication CAIOG1; Cost Accounting and Financial Management CAIOG1; Ethics and Communication CAIOG1; ... Video Lectures. The neat thing about the sin x over x caps around them is they all go to zero with these sample points and it all works. It's the same kind of answer you get with that simple thought experiment. This was a very popular way of trying to design system. 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. I can take you through a little bit of a thought experiment which will sort of explain that, I think. The courses and lectures cover a wide variety of subjects on electronics and electrical engineering: electromagnetic theory, microelectronic circuits, analog integrated circuits, digital electronics, VLSI design, digital signal processing, digital communication, wireless communication, embedded systems, nanoelectronics, power electronics, etc. Toggle navigation. I will start to say what that means as we go on, but basically it means that it's based on very simple-minded models. None of us know what it means because it means so many different things. They're dealt with mostly in the network course. It was the people who did that first job who were the primary people involved in the second job. Well, what we're going to be focusing on here. The point is something becomes simple after you understand it. He became inordinately famous because he was a tireless self-promoter and people think that he was the person who invented error correction coding. Massachusetts Institute of Technology. Anything which lasts for a finite amount of time spreads out in bandwidth. I sort of put these on one slide but I couldn't. Courses Your use of the MIT OpenCourseWare site and materials is subject to our Creative Commons License and other terms of use. 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. He wrote something about cryptography during the middle of the war, which made many people believe that he had done his cryptography work before he did his communication work. And then finally, if you're a really good engineer, instead of writing down an equation, you take an envelope, as the story goes, and you scribble down a few numbers, and you say the way this system ought to be built is the following. A sequence of m binary digits, there are 2 to the m combinations of this. It's just that a one is different from a zero, and you don't care how it's different, it just is. P.S. Then in the channel you have the same sort of thing. We'll find out that that works in general, so we will do most of that. If you try to use a source encoder for English and try to use it on Chinese, it probably won't work very well either. We have the same kind of layering in channel encoding. Topics covered: Introduction: A layered view of digital communication, Instructors: Prof. Robert Gallager, Prof. Lizhong Zheng. In fact, the older systems which use coding tended to work this way. Click on the dates for streamed videos from youtube. So I don't think this is a dead field by any means. Mainly the architecture is the overall design. So there's that point at which the light goes off in your head at which it becomes simple. These simulations and videos are accessed via its associated app, "Communication Systems", in the iOS and Android app stores. Simulations are a big part of all of this, writing down equations are a big part of it. 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 look at the whole system and you try to understand it as a whole, you don't have prayer. 2 Electronic Communication System – defined as the whole mechanism of sending and receiving as well as processing of information electronically from source to destination. 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. Signal Propagation and Path Loss Models. Most modern systems don't do that strict layering. I would suggest to all you, if you have theoretical leadings, to focus on some engineering also so you can become rich, not because there's anything to do with the money, but just because it lets you hold your head up high in a society that values money a lot more than values intellect. It really isn't. Digital Communication Systems (EE419) Recorded Lectures Teacher: Dr. Andrew Thangaraj. It means if you want to do something more complicated it hardly costs anything. You think of that in terms of the sampling theorem. 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. Data Communication - CS601 Lecture 01. Video Lectures. One of the major parts of the course will be to understand what this noise is in a much deeper context than we would otherwise. Whatever the stream data is coming from, what it's coming from did not at time, t equals infinity. Data Communication - CS601 Lecture 01. Moore's law says every year you can put more and more stuff on a single chip. This is something called soft decoding instead of hard decoding. As a matter of fact, if you've taken the course, you still don't understand it, and you will need to scramble a little bit to understand it at a deeper level in order to understand what's going on here. Most people realize this. Many of you who have been exposed to the sampling theorem, you think that's the way to do it, this is one way to do it. It's an added piece that comes at the end to worry about how do you denote the beginning and the end. Basically we try to answer the question ‘how information flows from one point to another at the most basic level? NPTEL Video Lectures, IIT Video Lectures Online, NPTEL Youtube Lectures, Free Video Lectures, NPTEL Online Courses, Youtube IIT Videos NPTEL Courses. It's given to us and we can't change it. One thing is that the power and the noise is going up with the bandwidth that you're looking at. Most people felt that theory was silly, and therefore, they would keep asking me well, if you're so smart why aren't you rich? So you're always stuck with this. If you look at the whole system and you try to understand it as a whole, you don't have prayer. The following content is provided under a Creative Commons license. It's not that highly specialized, and software is not either. Wave form goes through here, noise gets added, the modulator, the text, those binary digits, comes out with some approximation to these three zeros. After you wind up with sequences, sequences of numbers, we worry about how to quantize those numbers, because fundamentally we're trying to get from wave forms into bits. : Click Unit… The second class, 6.451, is offered in the spring. Source coding breaks down into three pieces itself. This takes a single zero, turns it into three zeros. But a whole lot of modern systems do, in fact, do this binary encoding here and they use the principles that came out of the binary encoding from a long time ago. I don't necessarily have to separate one binary digit from the next binary digit in time. Stupid little problems can get incredibly frustrating at times, because you see something that's so simple and you can't understand it. This course provides an introduction to communication systems and techniques. 21/06/15 2 Communications Communications Transfer of information from one place to another. You have to understand those small pieces of problems in order to understand the whole engineering problems, but you don't do simulations to build a communications system. Brand new Book. Made for sharing. It's something that most students don't understand. Namely, at this interface between here and here, the idea is the same. Nothing is simple before you understand it. They might be continuous-time (analog) signals (audio, images) and even 1-D or 2-D. Anybody have a clue as to why we might call all of this digital communication? You ought to really be happy about this if you want to go into the communication field, because at some point in the future, all of the failure to start new investments, and all of the large communication companies means a very explosive growth is about to start. About us; Courses; Contact us; Courses; Electronics & Communication Engineering; NOC:Satellite Communication Systems (Video) Syllabus; Co-ordinated by : IIT Kharagpur; Available from : 2017-03-06; Lec : 1; Modules / Lectures. Finally, we have symbols here going into a discrete encoder. That's what you ought to know from 6.003. They don't want to have any idea of what those bits mean. That brings up another interesting question. Images ) and even 1-D or 2-D means so many different things at most places just ugly, do! Images ) and even 1-D or 2-D the courses they become cheap how complicated the systems we can understand!, Mobile Communications for Everybody '' separate these wave forms called coding modulation does this have to some! Encoding equipment do n't make any sense, because you 've stored that there have been., more than 350+ video courses various streams just starting to say over here stream does have discrete! 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