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From: zador-anthony@cs.yale.edu (Tony Zador)
Newsgroups: sci.electronics
Subject: Information, channel capacity, and feedback
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Date: 10 Jan 91 00:28:13 GMT
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Suppose you have a source A and a destination B to which you are trying to
communicate.  Everything is continuous.
You have X units of channel capacity at your disposal (perhaps
they correspond to n thin filaments of cable, sold in small units of X/n).
If you string your channel from A to B, then according to Shannon
you can transmit X but no more information per unit time with
arbitrarily small error.  

What if you allow feedback?  That is, what if you have a channel of
Y capacity from A to B and X-Y units from B to A?  Does this win
you anything? Does Shannon cover this?  Is this even a well-posed 
question?

Thanks for any help,
Tony Zador
zador@cs.yale.edu