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Embedded and Real-Time Computing Systems and Applications, 2006. Proceedings. 12th IEEE International Conference on

Date 16-18 Aug. 2006

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Displaying Results 1 - 25 of 65
  • 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - Cover

    Page(s): c1
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  • 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - Title

    Page(s): i - iii
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  • 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - Copyright

    Page(s): iv
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  • 12th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - TOC

    Page(s): v - ix
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  • Foreward

    Page(s): x
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  • Conference organization

    Page(s): xi - xiii
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  • Reviewers

    Page(s): xiv
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  • Rate Monotonic Schedulability Conditions Using Relative Period Ratios

    Page(s): 3 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (173 KB) |  | HTML iconHTML  

    Feasibility and schedulability problems have received considerable attention from the real-time systems research community in recent decades. Since the publication of the Liu and Layland bound, many researchers have tried to improve the schedulability bound of the RM scheduling. The LL bound does not make any assumption on the relationship between any of the task periods. In this paper we consider the relative period ratios in a system. By reducing the difference between the smallest and the largest virtual period values in a system, we can show that the RM schedulability bound can be improved significantly. This research has also proposed a system design methodology to improve the schedulability of real-time system with a fixed system load View full abstract»

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  • Characterization and Analysis of Tasks with Offsets: Monotonic Transactions

    Page(s): 10 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (179 KB) |  | HTML iconHTML  

    This article introduces the concept of monotonic transactions. A monotonic transaction is a particular case of transactions for which the load arrival pattern is (or can be by rotation) localized at the beginning of the transaction. In the general context of tasks with offsets (general transactions) only exponential methods are known to calculate the worst-case response time. The pseudo-polynomial methods known give an upper bound of the worst-case response time. The method of analysis suggested in this article gives the real worst-case response time: moreover; this method has a complexity lower than that of the existing methods of approximation. There are two main steps in the application of this method: grouping the tasks of the transaction in a normal form and seeking a monotonic pattern View full abstract»

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  • Probabilistic Timing Join over Uncertain Event Streams

    Page(s): 17 - 26
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB) |  | HTML iconHTML  

    This paper addresses the problem of processing event-timing queries over event streams where the uncertainty in the values of the timestamps is characterizable by histograms. We describe a stream-partitioning technique for checking the satisfaction of a probabilistic timing constraint upon event arrivals in a systematic way in order to delimit the "probing range" in event streams. This technique can be formalized as a probabilistic timing join (PTJoin) operator where the join condition is specified by a time window and a confidence threshold in our model. We present efficient PTJoin algorithms that tightly delimit the probing range and efficiently invalidate events in event streams View full abstract»

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  • A Software Infrastructure for Wearable Sensor Networks

    Page(s): 27 - 35
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    In ubiquitous computing environments, context-awareness is one of the most important research topics. Computers embedded in our surrounding can extract information about a user, and the information makes it possible to offer personalized services according to the user's preference. To extract a large amount of context information, wearable sensor devices become more important in the near future. However, it is not easy to develop context-aware services that use context information from wearable sensor devices because of the gap between low-level sensor information and high-level context that the services require. In this paper, we propose a software infrastructure for wearable sensor networks. We first discuss the requirements to retrieve context information from wearable sensor networks. Then, we introduce our software infrastructure named Cinnamon that extracts high-level context from low-level context information retrieved from wearable sensor networks. The software infrastructure makes it dramatically easy to develop context-aware services for wearable sensor networks. We present the design and implementation of Cinnamon, and discuss our current prototype implementation View full abstract»

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  • objSampler: A Ubiquitous Logging Tool for Recording Encounters with Real World Objects

    Page(s): 36 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1122 KB) |  | HTML iconHTML  

    We propose a novel tool, called objSampler, with which users can record and recall "encounters" with objects in ubiquitous computing environments. We encounter various things, individuals, and places in the real world either consciously, meaning encounters that we are aware of, or unconsciously, meaning those we are unaware of but physically close to them. While some of those encounters are particularly important or treasurable to us, the physical memory in our brain is often too volatile to remember them. In objSampler, we address this issue by providing a state-of-art hardware called objPipette that embeds a sensor node, an RF-ID reader, and a battery cell. Users can record conscious encounters with it by scanning RF-ID tags pasted on real world objects. In addition, the objPipette detects and records the places where the user is. Users can recall the recorded encounters by using a software support in objSampler, called objScope. This paper describes the design and implementation of objSampler. User study, which is also provided in this paper, shows that objSampler provides a unique and intuitive means to achieve the above goal View full abstract»

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  • Algorithm Selectors for Providing Location Estimation Services within a Cellular Radio Network

    Page(s): 42 - 50
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (147 KB) |  | HTML iconHTML  

    Mobile location estimation is becoming an important value-added service for mobile phone operators. Many mobile location estimation algorithms based on the cellular radio networks have been proposed but there exists no general solution since each algorithm has its own advantage depending on specific terrain and environmental factors. In this paper, we propose and investigate three algorithm selectors, one with a LDA classifier and the other two with Bayes classifiers using either a Naive Bayes probabilistic model or a Bayes probabilistic model, to select the best mobile location estimation algorithms from our previous work in order to combine their merits, and provide a more accurate estimation for location services. We have tested these three algorithm selectors with real data taken in Hong Kong. Experiment results have shown that they are all useful in particular, and the one with a Bayes probabilistic model outperforms all other existing location algorithms among different kinds of terrains in terms of average errors View full abstract»

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  • Instruction Scheduling with Release Times and Deadlines on ILP Processors

    Page(s): 51 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB) |  | HTML iconHTML  

    ILP (instruction level parallelism) processors are being increasingly used in embedded systems. In embedded systems, instructions may be subject to timing constraints. An optimising compiler for ILP processors needs to find a feasible schedule for a set of time-constrained instructions. In this paper, we present a fast algorithm for scheduling instructions with precedence-latency constraints, individual integer release times and deadlines on an ILP processor with multiple functional units. The time complexity of our algorithm is O(n2 logd)+min{O(de), O(ne)}+min{O(ne), O(n2.376)}, where n is the number of instructions, e is the number of edges in the precedence graph and d is the maximum latency. Our algorithm is guaranteed to find a feasible schedule whenever one exists in the following special cases: 1) one functional unit, arbitrary precedence constraints, latencies in {0,1}, integer release times and deadlines; 2) two identical functional units, arbitrary precedence constraints, latencies of 0, integer release times and deadlines; 3) multiple identical functional units or multiple functional units of different types, monotone interval-ordered graph, integer release times and deadlines; 4) multiple identical functional units, in-forest, equal latencies, integer release times and deadlines. In case 1) our algorithm improves the existing fastest algorithm from O(n2 logn)+min{O(ne), O(n2.376)} to min{O(ne), O(n2.376)}. In case 2) our algorithm improves the existing fastest algorithm from O(ne+n2 logn) to min{O(ne), O(n2.376)}. In case 3) no polynomial time algorithm for multiple functional units of different types was known before View full abstract»

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  • Modeling Instruction-Level Parallelism for WCET Evaluation

    Page(s): 61 - 67
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (142 KB) |  | HTML iconHTML  

    The estimation of the worst-case execution time of hard real-time applications becomes very hard as more and more complex processors are used in real-time systems. In modern architectures, estimating the execution time of a single basic block is not trivial due to possible timing anomalies linked to out-of-order execution. The influence of preceding basic blocks on the pipeline state also has to be accounted for. Recently, graphs have been used to model the execution of a block on a dynamically-scheduled pipelined processor. In this paper we extend this model to express instruction-level parallelism so that superscalar processors with multiple functional units can be analyzed. Simulation results show how this extended model estimates WCETs tightly even when a realistic processor is considered. They also give an insight into the complexity of the model in terms of analysis time View full abstract»

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  • Optimization of Real-Time Systems Timing Specifications

    Page(s): 68 - 76
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    Real-time logic (RTL) is useful for the verification of a safety assertion SA with respect to the specification SP of a real-time system. Since the satisfiability problem for RTL is undecidable, there were many efforts to find proper heuristics for proving that SPrarrSA holds. However, none of such heuristics necessarily finds an "optimal implication". After verifying SPrarrSA, and the system implementing SP is deployed, performance changes as a result of power-saving, faulty components, and cost-saving in the processing platform for the tasks specified in SP affect the computation times of the specified tasks. This leads to a different but related SP, which would violate the original SPrarrSA theorem if SA remains the same. It is desirable, therefore, to determine an optimal SP with the slowest possible computation times for its tasks such that the SA is still guaranteed. This is clearly a fundamental issue in the design and implementation of highly dependable real-time/embedded systems. This paper tackles this fundamental issue by describing a new method for relaxing SP and tightening SA such that SPrarrSA is still a theorem. Experimental results show that less than 20% overhead of the running time of the algorithm for the verification of SPrarrSA is needed to find an optimal theorem View full abstract»

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  • Dynamic Adaptation of Stability Periods for Service Level Agreements

    Page(s): 77 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    A QoS adaptation to dynamically changing system conditions that takes into consideration the user's constraints on the stability of service provisioning is presented. The goal is to allow the system to make QoS adaptation decisions in response to fluctuations in task traffic flow, under the control of the user. We pay special attention to the case where monitoring the stability period and resource load variation of service level agreements for different types of services is used to dynamically adapt future stability periods, according to a feedback control scheme. System's adaptation behaviour can be configured according to a desired confidence level on future resource usage. The viability of the proposed approach is validated by preliminary experiments View full abstract»

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  • Relaxed Correctness for Firm Real-Time Databases

    Page(s): 82 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    Real-time database system must meet time constraints in addition to the integrity constraints. Concurrency control is one of the main issues in the studies of real-time database systems. Traditional concurrency control methods use serializability as the correctness criterion when transactions are executed concurrently. However, strict serializability as the correctness criterion is not always suitable in real-time databases. Instead, correctness requirements vary from one type of transactions to another and from one data type to another. In this paper we propose a concurrency control method witch is based on optimistic methods with a extension to relaxed serializability and semantic conflict resolution so that a special purpose concurrency control scheme can be applied. Proposed method is evaluated and tested in prototype implementation of real-time database system for telecommunications View full abstract»

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  • Mapping Task-Graphs on Distributed ECU Networks: Efficient Algorithms for Feasibility and Optimality

    Page(s): 87 - 90
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (126 KB) |  | HTML iconHTML  

    This mapping problem has to be solved in many application scenarios. In the automotive industry, for example, the implementation of car functions involves distributed task sets running on multiple electronic control units (ECU) with bus-based inter-task communication, a problem we consider in this paper. Our approach is based on mixed integer linear programming (MILP). MILP is concerned with optimizing a linear function subject to a set of linear constraints where some variables are required to be integer. The current state-of-the art method to solve integer programs is the branch-and-cut (B&C) algorithm and several industrial strength solvers are available. We describe a MILP-model for the mapping problem. Handling this model over to a general MILP-solver does not yield satisfactory results in terms of running time. To make the model more efficient we use the above ingredients: we incorporate a primal heuristic, strengthen the model with further inequalities and generate on-demand cutting planes, which violate the current fractional solution. These routines drastically speed up the solution time View full abstract»

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  • A Framework for Compositional and Hierarchical Real-Time Scheduling

    Page(s): 91 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    Hierarchical scheduling frameworks have lately received a lot of attention for component-based design of complex real-time systems. The specification of the resource reservation policy play a dominant role in such frameworks. In this context, the notion of real-time virtual resources results a very flexible representation of resource reservation schemes. We intend to combine the advantages offered by virtual resource scheduling with very general event models specified using real-time calculus. Our proposed framework permits resource partitioning to be extended to multiple levels and handles a wider range of scheduling algorithms and task models. In addition, it allows the handling of data dependencies between tasks from different task groups in the hierarchy View full abstract»

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  • Towards an Analysis of Garbage Collection Techniques for Embedded Real-Time Java Systems

    Page(s): 97 - 100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (107 KB) |  | HTML iconHTML  

    From a real-time perspective, the garbage collector (GC) introduces unpredictable pauses that are not tolerated by real-time tasks. Real-time collectors eliminate this problem but introduce a high overhead. Another approach is to use memory regions (MR) within which allocation and deallocation are customized. This facility is supported by the memory model of the real-time specification for Java (RTSJ). This paper provides an indepth analytical investigation of the problems and solutions of Java garbage collection techniques regarding it use in embedded real-time systems View full abstract»

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  • Garbage Collector Scheduling in Dynamic, Multiprocessor Real-Time Systems

    Page(s): 101 - 105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (271 KB) |  | HTML iconHTML  

    We present a garbage collector scheduling algorithm for dynamic multiprocessor real-time systems called GCMUA. The algorithm considers mutator activities that are subject to time/utility function time constraints, stochastic execution-time and memory demands, and overloads. We prove that GCMUA probabilistically lower bounds each mutator's accrued utility, lower bounds the total accrued utility, and upper bounds the assurances' sensitivity to variations in execution-time and memory demand estimates. Our simulation results confirm our analytical results View full abstract»

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  • Strengthening Property Preservation in Concurrent Real-Time Systems

    Page(s): 106 - 109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    To build a "correct" implementation from a model of a concurrent real-time system, it is important to understand the relation between the properties of the model and of its corresponding implementation. In this paper, the behaviour of a system is described with timed action sequences. Based on a notion of distance that expresses the observable property preservation between timed action sequences, we show that a stronger observable property preservation between model and implementation is obtained when urgency on the execution of observable actions is imposed over the execution of unobservable ones. Furthermore, we present a model synthesis approach and, by means of a case study, we show how it can be applied in the synthesis of real-time systems View full abstract»

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  • Security for Ubiquitous Computing: Problems and Proposed Solutionl

    Page(s): 110 - 116
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    Traditional authentication and access control are no longer suitable for ubiquitous computing paradigm. They are only effective if the system knows in advance which users are going to access and what their access rights are. Therefore, it calls for a novel security model. In this paper, we outline major security problems in ubiquitous computing and propose a new architecture, TBSI (trust-based security infrastructure). In TBSI, trust and risk management plays a key role to support authentication and authorization to unknown users. Meanwhile, intrusion detection and home firewall are also integrated to make TBSI more robust. This paper is an extension of our previous work to give more detailed description and enhancement of the architecture. TBSI is on-going research project to support our context-aware middleware CAMUS View full abstract»

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  • Deferrable Scheduling for Temporal Consistency: Schedulability Analysis and Overhead Reduction

    Page(s): 117 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (349 KB) |  | HTML iconHTML  

    The deferrable scheduling algorithm for fixed priority transactions (DS-FP) is demonstrated to be a very effective approach for minimizing real-time update transaction workload while maintaining temporal validity of real-time data. This paper examines the schedulability of deferrable scheduling and presents a sufficient condition. While its online scheduling overhead is a concern, we propose a hyperperiod based DS-FP approach satisfying the temporal validity constraint with low overhead. The algorithm, namely DEferrable Scheduling with Hyperperiod by Schedule Adjustment (DESH-SA), adjusts the DS-FP schedule in an interval so that the adjusted schedule in the interval can be repeated infinitely. Our experiments demonstrate that DESH-SA can reduce scheduling overhead of DS-FP and also achieve update workload near optimal View full abstract»

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