WIMAX (Worldwide Interoperability for Microwave Access) is a wireless communication protocol that provides longer range and higher bandwidth than WiFi. It uses a system of towers and receivers to provide internet access to homes and businesses over long distances without wires. WIMAX employs various techniques like ARQ, FEC and H-ARQ to make data transmission over the unreliable airlink more reliable. For ARQ, it uses methods like stop-and-wait, sliding window with go-back-N and selective repeat to handle lost packets. It also uses FEC codes for error correction and H-ARQ combines ARQ and FEC.