Test Of Qos Mechanism And Scheduling Algorithms In Wimax System

The WiMAX system based on the IEEE 802.16 standard is a popular next generation BWA (Broadband Wireless Access) system. Due to its advantages of high throughput, high capacity, low cost etc, the WiMAX system has been used all over the world, providing subscribers with high quality service.In the IEEE 802.16 standard, the PHY and MAC are defined in detail to form a unique air interface standard. And the QoS (Quality of Service) is introduced in the layer of MAC in IEEE 802.16 standard to meet the need of multiservice support. Although five types of services, along with associated bandwidth request and allocation algorithms, are defined in the IEEE 802.16 standard, the realization is not given, even any suggestion. Hence QoS mechanism and scheduling algorithms are issues in WiMAX research.This thesis, based on the deep research on the IEEE 802.16 standard, analysed the realization mechanism of MAC QoS mechanism. All five types services supported by MAC are introduced, including UGS, rtPS, ertPS, nrtPS and BE. UGS, rtPS and ertPS are real-time services while nrtPS and BE are non-real-time service. For each scheduling service, there is a set of QoS parameters to be configured to support the serivce. Parameters sucn as Minimum Reserved Traffic Rate, Maximum Sustained Traffic Rate, Maximum Latency, Tolerated Jitter, Unsolicited Polling Interval etc, are included. QoS mechanism is supported by CS (Service-specific Convergence Sublayer) and CPS (Common Part Sublayer) in MAC. Taking downlink for example, service data from upper layer will be classified and mapped to different connnections in CS, and then all the data of connections is scheduled by MAC bandwidth scheduling algorithms in CPS. MAC bandwidth scheduling can be divided into two stages, deadling scheduling and surplus scheduling. The deadline scheduling takes effect when the whole air interface bandwidth of system is not enough for all the users to meet their Minumum Reserved Traffic Rate. If the bandwidth is enough, then the surplus scheduling takes effect. In IEEE802.16 standard, the realization of scheduling algorithms is not given. Six scheduling algorithms including Sequence, WFQ, PFS, MAC C/I, Fair Throughput and Fair Time are analysed in this thesis. A test strategy for that QoS mechanism and bandwidth scheduling algorithms of two stages is designed. Further, a network platform comprised of UE (User Equipment), BS (Base Station) and CSN (Core Service Network) is set up to run the test plan. At last, the test results are given. Comparing with the outcomes in theory and considering the measure error, all the six scheduling algorithms are proved to be correct to allocate system air interface bandwidth.