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06.08.2005
Originally featured on BroadcastEngineering.com
Bandwidth and infinity reflections: Part II


Smart, communicative water bugs might point the way to infinite bandwidth, Robert Lucky tells his audience during the Engineering Luncheon at NAB2005.

Radiofrequency spectrum is a scarce resource–period, end of story. That’s the conventional wisdom upon which entire industries, government regulations and fortunes have been built.

However, author, inventor and engineer Robert Lucky, explained during the Engineering Luncheon at NAB2005 that RF spectrum might not be as finite as once thought. In fact, it might be infinite.

This edition of High Definition Technology Update, presents the second and concluding installment of excerpts from Lucky’s address: “Is Bandwidth Infinite?”

HDTU: Robert Lucky on interference.

Robert Lucky: I used to think I understood interference. I don’t have a clue any more. Interference is something you grow up with. And when someone on my right is transmitting on a frequency, and someone on my left is transmitting on the same frequency, they interfere.

That is not a proper description of the world. There is no interference in the physical world. That wave from the right passes right through the wave on the left like strangers passing in the night, and they don’t interact at all in space.

So interference is a property of the receiver. It has nothing to do with space. Of course, the FCC does not regulate receivers. It regulates transmitters.

HDTU: Lucky on cooperative diversity.

RL: There’s a new area of research called cooperative diversity, that has a lot of different approaches to it, that people believe cause infinite scaling so we could bring in an infinite number of transceivers into a given frequency and space.

In cooperative diversity — let’s go back to my water bug reference floating up and down unaware that there are two waves. But suppose there are other water bugs out there also floating up and down. Suppose the water bugs talk to each other, and communicate what they see. And then the water bugs — very clever water bugs — start to reconstruct, and realize there are two waves passing through each other and they are able to eliminate the interference. Now in cooperative diversity, every transceiver, if you all had was transceivers, would be able to be passed off to your neighbors so they could see what your antenna is seeing.

Now think of diversity in the old way where you have antennas that you are combining for diversity gain. In conceptual means you are able to take everyone else’s antenna and make use of them as if they were your own to put together the God’s eye view of what is happening.

There are many proposals about this depending upon whether you amplify what your antenna is seeing and pass it along, or whether you process it, and what kind of coding you might use. There is a whole lot of work going on right now. It isn’t proven but the concept is that you put scale to infinity with this kind of cooperative diversity.

There are two keys to scaling: You must have as many receivers as transmitters, and the other people must cooperate.

HDTU: Lucky on theory and reality.

RL: So this is all theoretical work that’s going on right now. In my last few seconds I am going to return to the title of my talk, which I never really got to: Is bandwidth infinite?

The answer is in theory, probably yes. But in practice, I don’t know how we get from here to the things I’ve been talking about — protecting the legacy environment that we have.

To check out Part I of the Lucky’s Engineering Luncheon speech at NAB2005, read Reflections on infinite bandwidth at NAB2005.

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