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Quality of Service and Resource Allocation in WiMAXFig Part 2

Tham khảo tài liệu 'quality of service and resource allocation in wimaxfig part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 16 Quality of Service and Resource Allocation in WiMAX Fig. 6. Flowchart of the scheduling algorithm Wu 2010 . 4.2.4.1 Performance evaluation The performance analysis of the scheduling scheme above described is performed by simulations. The main parameters of the simulation are the following the PHY layer is OFDM the MCS is 64QAM 3 4 and the frame duration is 5 ms. The compared performance metrics are latency jitter throughput and the rate of packet loss. The results showed that the scheduling scheme can reduce the average latency and achieve the QoS. 4.3 Cross layer approach algorithms 4.3.1 Temporary Removal Scheduler TRS The TRS scheduler makes the scheduling list in accordance with the SSs that have Signal Interference Ratio SIR greater than a preset threshold Ball 2005 . When the radio conditions are poor then the scheduler suspends the packet call from the scheduling list for an adjustable time period Tr. The scheduling list contains all the SSs that can be served at the next frame. When the Tr expires the suspended packet is checked again and if the radio conditions are still poor the packet is suspended for another time period Tr. This process is repeated L times where L is equal to consecutive suspend procedure. The TRS scheduler can be combined with the Round Robin RR and maximum Signal to Interface Ratio mSIR schedulers. When TRS is combined with RR the whole radio resources are divided by the number of subscribers in the list and all the subscribers will get resources equitably. Scheduling Mechanisms 17 4.3.2 UAF WiMAX scheduler The UAF_WiMAX scheduler was developed in Khan et al. 2010 . The scheduler serves the SSs with minimum signal to interface ratio taking into account the already allocated resources to the SSs which have greater signal to interface ratio. When the BS provides periodical unicast request polling to the subscribers the subscribers respond with their required bandwidth request that is equal to its uplink data connection queue. The .