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Applications such as video and audio streaming, online gaming, video conferencing, Voice over IP (VoIP) and File Transfer Protocol (FTP) demand a wide range of QoS requirements such as bandwidth and delay. Existing wireless technologies that can satisfy the requirements of heterogeneous traffic are very costly to deploy in rural areas and “last mile” access. Worldwide Interoperability for Microwave Access (WiMAX) provides an affordable alternative for wireless broadband access supporting a multiplicity of applications. The IEEE 802.16 standard provides specification for the Medium Access Control (MAC) and Physical (PHY) layers for WiMAX. A critical part of the MAC layer specification is scheduling, which resolves contention for bandwidth and determines the transmission order of users. It is imperative for a scheduling algorithm to have a multi-dimensional objective of satisfying QoS requirements of the users, maximizing system utilization and ensuring fairness among the users. In this thesis, we categorize and study various scheduling algorithms for the uplink traffic in WiMAX in view of these objectives. The algorithms are studied under different mixes of traffic and for various characteristics of the IEEE 802.16 MAC layer such as uplink burst preamble, frame length, bandwidth request mechanisms etc. Simulation results indicate that legacy algorithms are not suitable for the multi-class traffic in WiMAX as they do not explicitly incorporate the WiMAX QoS parameters. We provide recommendations for enhancing existing scheduling schemes in WiMAX, and shed light on some of the open issues that need to be addressed. / Thesis (Master, Computing) -- Queen's University, 2007-12-29 18:21:21.521

The development of wide-area networks and the availability of powerful computers as low-cost commodity components are changing the face of computation. These progresses in technology make it possible to utilize geographically distributed resources in multiple owner domains to solve large-scale problems in science, engineering and commerce. Research on this topic has led to the emergence of Grid computing. To achieve the promising potentials of tremendous distributed resources in the Grid, effective and efficient scheduling algorithms are fundamentally important. However, scheduling problems are well known for their intractability, and many of instances are in fact NP-Complete. The situation becomes even more challenging in the Grid circumstances due to some unique characteristics of the Grid. Scheduling algorithms in traditional parallel and distributed systems, which usually run on homogeneous and dedicated resources, cannot work well in the new environments. This work focuses on workflow scheduling algorithms in the Grid scenario. New challenges are discussed, previous research in this realm is surveyed, and novel heuristic algorithms addressing the challenges are proposed and tested. The proposed algorithms contribute to the literature by taking the following factors into account when a schedule for a DAG-based workflow is produced: predictable performance fluctuation and non-deterministic performance model of Grid resources, the computation and data staging co-scheduling, the clustering characteristic of Grid resource distribution, and the ability to reschedule according to performance change after the initial schedule is made. The performance of proposed algorithms are tested and analyzed by simulation under different workflow and resource configurations. / Thesis (Ph.D, Computing) -- Queen's University, 2009-04-23 22:30:09.646

Database Management Systems (DBMSs) are an integral part of many applications. Web-based applications, such as e-commerce sites, are faced with highly variable workloads. The number of customers browsing and purchasing items varies throughout the day and business managers can further complicate the workload by requesting complex reports on sales data. This means the load on a database system can fluctuate dramatically with a sudden influx of requests or a request involving a complex query. If there are too many requests operating in the DBMS concurrently, then resources are strained and performance drops. To keep the DBMS’s performance consistent across varying loads, a load control system can be used. This thesis investigates the concept of a load control system based on regulating individual resource usage in a predictive manner. For the purpose of this proof-of- concept study, we focus on a specific resource; namely, the sort heap. A method of estimating sort heap usage based on the query execution plan is presented and several scheduling methods based on these estimations are proposed. A prototype load control system is used to evaluate and compare the scheduling methods. Experiments show that it is possible to both estimate sort heap requirements and to control sort heap usage using our load control system. / Thesis (Master, Computing) -- Queen's University, 2011-06-09 11:02:31.595

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No-wait scheduling problem refers to the set of problems in which a number of jobs are available for processing on a number of machines with the added constraint that there should be no waiting time between consecutive operations of the jobs. It is well-known that most of the no-wait scheduling problems are strongly NP-hard. Moreover, no-wait scheduling problems have numerous real-life applications. This thesis studies a wide range of no-wait scheduling problems, along with side constraints that make such problems more applicable. First, 2-machine no-wait flow shop problem is studied. Afterwards, setup times and single server constraints are added to this problem in order to make it more applicable. Then, job shop version of this problem is further researched. Analytical results for both of these problems are presented; moreover, efficient algorithms are developed and applied to large instances of these problems. Afterward, general no-wait flow shop problem (NWFS) is the focus of the thesis. First, the NWFS is studied; mathematical models as well as metaheuristics are developed for NWFS. Then, setup times are added to NWFS in order to make the problem more applicable. Finally, the case of sequence dependent setup times is further researched. Efficient algorithms are developed for both problems. Finally, no-wait job shop (NWJS) problem is studied. Literature has proposed different methods to solve NWJS; the most successful approaches decompose the problem into a timetabling sub-problem and a sequencing sub-problem. Different sequencing and timetabling algorithms are developed to solve NWJS. This thesis provides insight to several no-wait scheduling problems. A number of theorems are discussed and proved in order to find the optimum solution of no-wait problems with special characteristics. For the problems without such characteristics, mathematical models are developed. Metaheuristics are utilized to deal with large-instances of NP-hard problems. Computational results show that the developed methods in this thesis are very effective and efficient compared to the competitive methods available in the literature.