Quality of Service (QoS) Support

With fast air link, symmetric downlink/uplink capacity, fine resource granularity and a

flexible resource allocation mechanism, Mobile WiMAX can meet QoS requirements for

a wide range of data services and applications.

In the Mobile WiMAX MAC layer, QoS is provided via service flows as illustrated in

Figure 8. This is a unidirectional flow of packets that is provided with a particular set of

QoS parameters. Before providing a certain type of data service, the base station and

user-terminal first establish a unidirectional logical link between the peer MACs called a

connection. The outbound MAC then associates packets traversing the MAC interface

into a service flow to be delivered over the connection. The QoS parameters associated

with the service flow define the transmission ordering and scheduling on the air interface.

The connection-oriented QoS therefore, can provide accurate control over the air

interface. Since the air interface is usually the bottleneck, the connection-oriented QoS

can effectively enable the end-to-end QoS control. The service flow parameters can be

dynamically managed through MAC messages to accommodate the dynamic service

demand. The service flow based QoS mechanism applies to both DL and UL to provide

improved QoS in both directions. Mobile WiMAX supports a wide range of data services

and applications with varied QoS requirements. These are summarized in Table 4.