Читать книгу Digital Communications 1 - Safwan El Assad - Страница 31

Claude Shannon introduced the concept of channel capacity, to measure the efficiency with which information is transmitted, and to find its upper limit.

The capacity C of a channel: (information bit/symbol) is the maximum value of the mutual information I(X, Y) over the set of input symbols probabilities

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The maximization of I(X, Y) is performed under the constraints that:

The maximum value of I(X, Y)occurs for some well-defined values of these probabilities, which thus define a certain so-called secondary source.

The capacity of the channel can also be related to the unit of time (bitrate Ct of the channel), in this case, one has:

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The channel redundancy Rc and the relative channel redundancy pc are defined by:

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The efficiency of the use of the channel is defined by

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