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In real-time theory, basically two approaches for the computation of response-times exist. One of them is the busy window method, the other is the real-time calculus, an extension of the network calculus. While both can be used to compute the bounds of response-times, they have different properties that make them suitable for different system architectures. The busy window approach on the one hand...
Theoretical real-time research generally neglects context switch times. But in recent embedded applications which consist of dozens of threads with very short execution times, their impact is too serious to be ignored. We present a hard real-time scheduling algorithm that perfectly hides the context switch times of an arbitrary number of threads. It requires a Simultaneous Multithreaded (SMT) processor...
This paper proposes SPLiT (Scalable Performance Library Tool) as the methodology to improve performance of applications on multicore processors, through CPU, and cache optimizations. SPLiT analyzes applications based on cycle counts, and cache misses, and predicts behavior of the applications according to the analysis. With these acquired knowledge on the target application, SPLiT improves CPU resource...
In RFID systems, middleware is used to filter enormous streaming data gathered continuously from readers to process application requests. The high volume of data makes middleware often in a highly overloaded situation. Nowadays, readers are becoming smart and provide filtering functionality. The reader filtering capability can be used to reduce data volume as well as middleware work-load. However,...
Desirable application performance is typically guaranteed through the use of Service Level Agreements (SLAs) that specify fixed fractions of resource capacities that must be allocated for unencumbered use by the application. The mapping between what constitutes desirable performance and SLAs is not unique: multiple SLA expressions might be functionally equivalent. Having the flexibility to transform...
While the dynamic voltage scaling (DVS) techniques are efficient in reducing the dynamic energy consumption for the processor, varying voltage alone becomes less effective for the overall energy reduction as the static power is growing rapidly. On the other hand, Quality of Service (QoS) is also a primary concern in the development of today's pervasive computing systems. In this paper, we propose...
With a good location estimation integrated into a Wi-Fi surveillance system, system administrator can closely monitor the network traffic as well as the behavior of the mobile users. Hence, there is a growing demand to have a quick and efficient way to indentify a specific group of people, or devices or asset within a controlled wireless network. In our proposed system, all the Wi-Fi traffic and information...
Real-time activity recognition using body sensor networks is an important and challenging task and it has many potential applications. In this paper, we propose a real time, hierarchical model to recognize both simple gestures and complex activities using a wireless body sensor network. In this model, we first use a fast, lightweight template matching algorithm to detect gestures at the sensor node...
The correctness of a real-time system depends on not only the system's output but also on the time at which results are produced. A hard real-time system is required to complete its operations before all its timing deadlines. For a given task set it is useful to know what is the minimum speed of the processor that will deliver a schedulable system. It is also beneficial in an engineering context to...
Limited preemption models have been proposed as a viable alternative between the two extreme cases of fully preemptive and non-preemptive scheduling. In particular, allowing preemption to occur only at predefined preemption points reduces context switch costs, simplifies the access to shared resources, and allows more predictable estimations of worst-case execution times. Current results related to...
This paper presents Rapid RT, a novel statistical approach to Worst-Case Response-Time (WCRT) analysis targeting complex embedded real-time systems. The proposed algorithm combines Extreme Value Theory (EVT) and other statistical methods in order to produce a probabilistic WCRT estimate. This estimate is calculated using response time data from either Monte Carlo simulations of a detailed model of...
Cluster scheduling, where processors are grouped into clusters and the tasks that are allocated to one cluster are scheduled by a global scheduler, has attracted attention in multiprocessor real-time systems research recently. In this paper, by adopting optimal global schedulers within each cluster, first we investigate the worstcase utilization bound for cluster scheduling. Specifically, for a system...
NAND flash memory has gained its popularity in a variety of applications as a storage medium due to its low power consumption, non-volatility, high performance, physical stability, and portability. In particular, Multi-Level Cell (MLC) flash memory, which provides a lower cost and higher density solution, has occupied the largest part of NAND flash-memory market share. However, MLC flash memory also...
The verification complexity of real-time requirements in embedded systems grows exponentially with the number of applications, as resource sharing prevents independent verification using simulation-based approaches. Formal verification is a promising alternative, although its applicability is limited to systems with predictable hardware and software. SDRAM memories are common examples of essential...
This paper proposes semi-fixed-priority scheduling to achieve both low-jitter and high schedulability. Semi-fixed-priority scheduling is for the extended imprecise computation model, which has a wind-up part as a second mandatory part and schedules the part of each extended imprecise task with fixed-priority. This paper also proposes a novel semi-fixed-priority scheduling algorithm based on Rate Monotonic...
In multitasking real-time systems it is required to compute the WCET of each task and also the effects of interferences between tasks in the worst case. This is complex with variable latency hardware usually found in the fetch path of commercial processors. Some methods disable cache replacement so that it is easier to model the cache behavior. Lock-MS is an ILP based method to obtain the best selection...
The job description of caches is to speed up memory accesses in the average case. Their intrinsic unpredictability however can seriously hamper the practicality and trustworthiness of system analysis and validation. In effect, this conflict asks system designers to take side between best average-case performance and maximum assurance, since both can't be had. In this paper we study the I-cache predictability...
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