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Real-time systems are those whose correctness depends not only on logical results of computations, but also on the time at which the results are produced. This thesis provides a formal definition for real-time systems and includes the following original contributions on real-time scheduling algorithms. The first topic studied in the thesis is minimizing the total penalty to be paid in scheduling a set of soft real-time tasks. The problem is NP-hard. We prove the properties of any optimal scheduling algorithm. We also derive a number of heuristic algorithms which satisfy the properties obtained. Moreover, we obtain a tight upper bound for the optimal solution to the problem. Numerical results that compare the upper bound with the optimal solution and the heuristic algorithms are provided. In the second part of this thesis, we study the problem of minimizing the number of processors required for scheduling a set of periodic preemptive independent hard real-time tasks. We use a partitioning strategy with an EDF scheduling algorithm on each processor. The problem is NP-hard. We derive lower and upper bounds for the number of processors required to satisfy the constraints of the problem. We also compare a number of heuristic algorithms with each other and with the bounds derived in this research. Numerical results demonstrate that our lower bound is very tight. In the third part of the thesis, we study the problem of uplink scheduling in telecommunication systems with two dimensional resources. Our goal is to maximize the total value of the packets sent in uplink subframe such that system constraints and requirements are satisfied. The packets have various QoS requirements and have either soft or hard deadlines. We take two approaches, namely 0-1 and fractional approaches, to model the problem. Considering the properties of the application, we derive globally optimal solutions in polynomial time for the models. We also present a method to fine-tune the models. Numerical results are provided to compare the performance of the various optimal algorithms each corresponding to a model. / Thesis (Ph.D, Computing) -- Queen's University, 2009-04-24 08:22:04.238

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ABB SA Products designs and manufactures complex real-time systems. The real-time properties of the system are hard to measure and test especially in the long run, e.g.  monitoring a system for months out in the real environment. ABB have started developing their own tool called JobMon for monitoring timing requirements, but they needed to measure more properties than time and in a more dynamic way than JobMon is constructed today. The tool must be able to measure different kind of data and be able to be monitor as long as the system itself. This thesis first does a survey and evaluation on existing commercial tools and if there exists a tool that can be integrated to the system and fulfill all demands. Different trace recorders and system monitoring tools are presented with its properties and functions. The conclusion is that there is no such tool and the best solution is to design and develop a new tool. The result is SysMon, a dynamic generic framework for measuring any type of data within a real-time system. The main focus for measuring during this thesis is time measurements, but no limits or assumptions of data types are made, and during late steps of the development new types of measurements are integrated. SysMon can also handle limits for measurements and, if required, take pre-defined actions e.g. triggering a logging function and saving all information about the measurement that passed the limit. The new tool is integrated to the system and evaluated thoroughly. It is an important factor to not steal too much resource from the system itself, and therefore a measurement of the tool’s intrusiveness is evaluated. / ABB SA Products designar och konstruerar komplexa realtidssystem. Realtidsegenskaperna för systemen är svåra att mäta och testa, speciellt under långa tidsperioder, t.ex. under drift i dess riktiga miljö under månader av online tid. ABB SA Products har börjat utvecklat ett eget verktyg, JobMon, för att kunna övervaka och mäta egenskaper i form av tid. Men behovet är större än att endast mäta tid och alla möjliga slags data behöver övervakas och utvärderas. Det här examensarbetet gör först en undersökning och utvärdering av existerande kommersiella verktyg och om det redan finns ett verktyg som uppfyller alla krav. Olika tracerecorders och systemövervakningsverktyg är presenterade med dess egenskaper och funktioner. Slutsatsen är till sist att det inte finns något existerande verktyg och att den bästa lösningen är att utveckla ett nytt verktyg. Resultatet är SysMon, ett dynamisk generisk ramverk för att mäta vilken form av data som helst. Huvudfokus under examensarbetet är tidsmätningar, men inga antaganden om vilka datatyper som kan användas görs. Under den senare delen av examensarbetet implementeras också en ny typ av mätning i system ticks. SysMon kan också hantera gränser för mätningar och, om nödvändigt, exekvera fördefinierade funktioner, t.ex. trigga en loggning och spara nödvändig information om mätningen som överskred gränsen. Det nya verktyget blir integrerat i systemet och testat noggrant. Det är viktigt att verktyget inte tar för mycket resurser från det normala systemet och därför utförs även en utvärdering av hur resurskrävande verktyget är.

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