Part of it is that the success in the communication field, most of the successes, have come out of a more scientific effort. His fundamental studies on quadrature amplitude modulation and detection led directly to the bps modems that provided Codex’s commercial success. I don’t view them as different because to me when I’m finding upper bounds on error probability, I’m simultaneously thinking of how does one achieve those bounds? And a coding system to find the right way of looking at modulation versus coding, which in a sense are really two ways of looking at the same thing. The more mathematically-inclined students and faculty would develop more sophisticated things.

The Defense Department as a whole wanted to see it happen. It was really kind of silly when I look back on it. So that all data compression works that way. That’s what computers are built out of. What was it like? People were developing chips.

Explained: Gallager codes

Irregular LDPC codes are defined by specifying the distribution of the node degrees in their Tanner graphs. By using this site, you agree to the Terms of Use and Privacy Policy.

Even though there were no obvious commercial projects, the money was there from the military. If the classic point-to-point communication system has data coming in at constant rate and data going out at constant rate, you need a big buffer in the middle if you’re going to use any of these data thesos techniques.

People used to say that all ways of communicating are good, except the ones you can think of!

Robert G. Gallager — Information Theory Society

There was a lot of interesting theory going on concerning the control of large systems. For gallayer years I thought I must be very naive because I couldn’t understand why all these people thought that these things were going to be used immediately because it didn’t seem like they were going to be used immediately.


It was an idea that the field passed by for about 30 years because computational techniques got so much better that nobody cared about doing things the simplest way. There were some civilians on the base who seemed to be castoffs from Fort Monmouth. I guess I questioned what we gallageg doing because I wondered why we were developing these very high-tech things which could be used only by the military, when I saw various civilian communication systems not really moving ahead very quickly.

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robert gallager phd thesis

I mean, most of us who are involved in this kind of thing don’t actually build the hardware ourselves. He’s at Zurich now, at ETH. As our networks get faster and faster, that problem becomes much more important because suddenly these systems get so complicated that people can’t understand them.

How do you save money by having diskless work stations? They were trying to develop early modems for agllager commercial market, thesjs they weren’t very far along in that yet. One of the earliest and best papers that I wrote was on something called the coding theorem.

All go over one line, all go out there, all get mixed up throughout the network. Like if you’re trying to get tasks done with a bunch of different people, you try to organize how that gets done, and you think in very distributive terms then.

robert gallager phd thesis

But in fact this turned out to be easier there because the problems sort of stay the same. I was telling you a little bit about this person yesterday when we were talking about all-optical networks. It was really kind of silly when I look back on it. It’s probably been the limiting factor in computer systems for many, many years, and it’s leading to all the parallel processing which is going on in the computer industry now, where again communication is the major problem. Suddenly I realized that the best way to learn something was not to read what somebody else had interpreted, but to go to the person who had done it and to read it at the source.


A little bit insofar as teaching these courses.

Low-density parity-check codes

An LDPC code is, strictly defined, a code that has gaallager representation using a sparse parity check matrix, i. I’m sitting with Dr. There was a theoretical background of lambda calculus and logic and recursive function theory that forms the theoretical background of what was going on in the computer language field.

robert gallager phd thesis

But anyway, after about two years of that, I came to MIT as a graduate student, primarily because I wanted to get out of the army early. In a sense in those days I was working on the wrong problem again.

It was something called threshold decoding, which is another practical way of decoding convolutional codes. And that’s just the beginning.

Oh, I was talking about the split between more practically-oriented and more theoretically-oriented engineers. There was Tukeya famous statistician. I think this was part of the reason why the effort in error correction slowed down for a while around I’m tgesis sure if you meant throughout the brief history of data networks or between communications issues and data networks.