Throughout this section, we discuss some of the salient features of
WiMAX, including WiMAX Mesh and how it fares in its ability to deliver carrier-grade
Ethernet services.
MAC
Multiple Access Control (MAC) is the protocol that defines the method of access to the
shared medium by multiple devices. WiMAX provides a fairly sophisticated MAC protocol
that enables efficient utilization of resources, while being independent of the details
of the Physical Layer Protocol (PHY). Unlike other popular MAC standards that do
not have a central controller (e.g., 802.3, 802.11, etc.), WiMAX uses a central controller,
referred to as the Base Station (BS), which coordinates access to the wireless medium
by all other devices, referred to as Subscriber Stations (SSs). In PMP networks, communications
from BS to SS, referred to as downlink (DL), and communications from SS
to BS, referred to as uplink (UL), are scheduled by the BS. In Mesh networks, a central
controller, referred to as the Mesh BS, schedules all communications (Mesh also allows
for distributed scheduling).
Each WiMAX device is uniquely identified by a 48-bit MAC address. It is used for
the purpose of initial authentication and registration of a SS during its entry into a
WiMAX network.
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