Information Theory and Coding > Channel Capacity > What is Channel Capacity?

Channel Capacity:

Consider a DMC having an input alphabet X= {xo, x1, ... , xq-1} and an output alphabet Y= {y_o, x₁, ... , x_Q-1}. Let us denote the set of channel transition probabilities by p_ji=P(y_i/x_j). The average mutual information provided by the output Y about the input X is given by

The maximum value of the average mutual information, I(X; Y), over the set of input symbol probabilities P(x) is a quantity that depends only on the channel transition probabilities P(y/x ). This quantity is called the Capacity of the Channel (C).

The units of channel capacity is bits per channel i.e. logarithm based on 2.

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Shannon’s theorem: on channel capacity

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