Tham khảo tài liệu 'quality of service and resource allocation in wimaxfig part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Scheduling Algorithm and Bandwidth Allocation in WiMAX 91 The IEEE standard provides specification for the MAC and PHY layers for WiMAX and there are several challenges for QoS guarantee in WiMAX. In the physical layer one challenge is the uncertainty of the wireless channel which makes the guarantee of broadband wireless data service difficult and renders the static resource allocation scheme unsuitable. In the MAC layer one challenge is the diversified service types which requires the WiMAX scheduling scheme to be adaptive to the various QoS parameters of different service types. There have been some studies of the WiMAX MAC scheduling problem 3 4 5 and 6 . The key components in WiMAX QoS guarantee are the admission control and the bandwidth allocation in BS. WiMAX standard defines adequate signalling schemes to support admission control and bandwidth allocation but does not define the algorithms for them. This absence of definition allows more flexibility in the implementation of admission control and bandwidth allocation. The research problem being investigated here is after connections are admitted into the WiMAX network how to allocate bandwidth resources and perform scheduling services so that the QoS requirements of the connections can be satisfied. What is QoS QoS refers to the ability of a network to provide improved service to selected network traffic over various underlying technologies including wired-based technologies Frame Relay ATM Ethernet and networks SONET and IP-routed networks and wireless-based technologies 3G IMS etc . In particular QoS features provide improved and more predictable network service by providing the following services Supporting dedicated bandwidth Improving loss characteristics Avoiding and managing network congestion Shaping network traffic Setting traffic priorities across the network Due to the differences in the wired-based and wireless-based access technologies the detailed .
