The significance of the famous Shannon's publication "A mathematical theory of communication" is discussed. The author states that this theory was a breakthrough for the times it was created. The present-day communications is so highly developed, that some old maxims should be up-dated, particularly the definition of the lower bound of signal reception. The author claims that this bound is no longer a constant value, ln(2), as the Shannon's theory states, but depends on many factors such, as the ratio of bandwidth-to-information transmission rate, the class of a receiver (adaptive, cognitive, MIMO1), the kind of reception system (on-line or off-line), and - of course - on the characteristics of noise, including entropy. Then, an absolute limit (Eb/N0)abs = 0 is suggested. An example of an advanced adaptive system approaching this bound is given.
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