How do you design an equalizer for multipath channel compensation?

Equalizers compensate inter-symbol interference (ISI) from multipath. Types: Linear equalizers (ZF forces zero ISI but enhances noise, MMSE balances ISI and noise), Decision feedback (DFE uses decisions to cancel post-cursor ISI, sensitive to error propagation), and Maximum likelihood sequence estimation (MLSE via Viterbi, optimal but exponential complexity with channel length). Adaptive algorithms: LMS (simple, slow convergence), RLS (fast, higher complexity). OFDM uses frequency-domain equalization (one-tap per subcarrier). Design considerations: Training sequence for channel estimation, tracking speed, complexity, and interaction with FEC.