A Performance Study of Downlink Scheduling Algorithms in Wireless Broadband Networks

IEEE 802.16 is also known as WiMAX was developed to produce high performance in Broadband Wireless Access (BWA) systems with a lower deployment cost than wired broadband services. Like other broadband services, IEEE 802.16 is designed to support applications such as Voice over IP (VoIP), video streaming, video conferencing and online gaming. In IEEE 802.16 standard, five types of service classes have been formed to cater the Quality of Service (QoS) needs for different applications. However, the standard does not state any specific scheduling algorithms for either uplink or downlink transmission. Therefore, scheduling algorithm implementations are depending on the vendors, service providers and researchers. In our presented work, an analysis of various available scheduling algorithms in wireless environment has been carried out. Upon the literature study and analysis, Round Robin (RR), Strict Priority (SP), Self-Clock Fair (SC) and Weighted Fair Queuing (WFQ) were tested in downlink scheduling. For each scheduling algorithm, two scenarios were created, 1) 64QAM and 2) the combination of 16QAM & 64QAM. Simulation results indicate that all the schedulers were struggling to perform as the number of Subscriber Station (SS) increases. Furthermore, the impact on having bad quality channel, which is 16QAM, is also one of the reasons that produces poor performance among all the schedulers. Hence, the traditional schedulers are not suitable for the uncertainty condition in wireless environment because they do not satisfy the QoS demand in WiMAX. 

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