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Media access control layer


The primary job of the MAC layer is to provide an interface between the PHY layer and upper layer protocols. Each instance of the MAC layer in a fixed/mobile WiMAX station has a 48-bit address as defined by the IEEE Std 802. Unlike the distributed and connectionless 802.11 MAC, the WiMAX MAC is centralized and connection-oriented. A 16-bit connection identifier (CID) identifies each WiMAX connection. Each WiMAX MAC layer protocol data unit uses the CID, instead of the MAC address, to identify source and destination. WiMAX has a rich quality of service mechanism that is based on the Data Over Cable Service Interface Specifications (DOCSIS).


Physical layer

The fixed/mobile WiMAX PHY layer uses a technology called orthogonal frequency division multiplexing (OFDM). OFDM techniques have been around for decades. The technology is now commonplace in wireless systems such as Wi-Fi. OFDM evolved from earlier single-carrier modulation systems and frequency division multiplexing systems. OFDM is a type of frequency division multiplexing system that provides better channel throughput because all of the underlying sub-carriers are orthogonal to one another.