Entropy, Capacity & Coding
Claude Shannon's Mathematical Theory of Communication. Entropy \(H(X) = -\sum_{i=1}^n p(x_i) \log_2 p(x_i)\) quantifies average uncertainty in bits. Binary Entropy function \(H_b(p) = -p\log_2 p - (1-p)\log_2(1-p)\). Huffman coding produces optimal prefix-free binary trees with average length \(H(X) \le \bar{L} < H(X) + 1\). Channel Capacity of a Binary Symmetric Channel (BSC) with error probability \(p\) is \(C = 1 - H_b(p)\).