The
standard defines four types of services: Unsolicited Grant Service (UGS), realtime
Polling Service (rtPS), non-real-time Polling Service (nrtPS), and Best-effort
Service (BE). The details of these services and their scheduling are discussed later
in section ???Scheduling of Services.???
WiMAX 475
Bandwidth Requests and Allocation The success of the very centralized WiMAX MAC
protocol in serving the QoS needs of the service flows depends on its effectiveness in
serving the bandwidth demands of the flows. Specifically, it depends on having an effective
mechanism for the SS to request for uplink bandwidth and for BS to timely allocate
the requested bandwidth on a dynamic basis.
The requests are made by SSs to the BS on per-connection basis. Bandwidth grants
are made by the BS scheduler based on multitude of parameters such as QoS parameters,
bandwidth usage and other pending requests. However, bandwidth grants are
made to the requesting SS without being specific about the CID for which the bandwidth
grant is made. This allows for SS to use the allocated bandwidth for whatever
fits its need. For example, if an SS has an urgent need to send a MAC management
message to the BS, it could use its allocated bandwidth for this purpose.
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