WiMAX-MAC Layer:


The MAC layer is responsible to provide a medium-independent interface to the physical (PHY) layer.

Must Read>> WiMAX-Physical (PHY) Layer

It was designed for point to multipoint broadband wireless access. It addresses the need for high bit rates for uplink and downlink. 

To support services like voice, multimedia the MAC layer is equipped to accommodate continuous and bursty traffic. 

To facilitate the more demanding physical environment and different service requirements of frequencies between 2 and 11 GHz, WiMAX is upgrading the MAC to provide Automatic Repeat Request (ARQ) and support for mesh architecture.

The 802.16 MAC is designed for point-to-multipoint (PMP) applications and is based on Collision Sense Multiple Access with Collision Avoidance (CSMA/CA).

The MAC incorporates several features suitable for a broad range applications at different mobility rates, such as the following: 

  1. Privacy Key Management (PKM) for MAC layer security. PKM version 2 incorporates support for extensible authentication protocol (EAP).
  2. Broadcast and multicast support.
  3. Manageability primitives.
  4. High-speed handover and mobility management primitives.
  5. Three power management levels, normal operation, sleep, and idle. 
  6. Header suppression, packing, and fragmentation for efficient use of spectrum.
  7. Five service classes, unsolicited grant service (UGS), real-time polling service (rtPS), non-real-time polling service (nrtPS), best effort (BE and Extended real-time variable rate (ERT-VR) service.

These features combined with the inherent benefits of scalable OFDMA make WiMAX suitable for high-speed data and bursty or isochronous multimedia applications.

Support for QoS is a fundamental part of the WiMAX-MAC layer design WiMAX borrows some of the basic ideas behind its QoS design from the DOCSIS cable modem standard. Strong QoS control is achieved by using a connection-oriented MAC architecture, where all downlink and up connections are controlled by the serving Base Station.

WiMAX also defines a concept of a service flow. A service flow is a unidirectional flow of packets with a particular set of QoS parameters and is identified by a Service Flow Identifier (SFID).

Must Read>> WiMAX Technology: Principles and Layers

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