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  • 51.
    Lim, Tiong Hoo
    et al.
    University of York.
    Bate, Iain
    University of York.
    Timmis, Jon
    University of York.
    Multi-modal routing to tolerate failures2011In: Proceedings of the 2011 7th International Conference on Intelligent Sensors, Sensor Networks and Information Processing, ISSNIP 2011, 2011, p. 211-216Conference paper (Refereed)
    Abstract [en]

    Reactive routing protocols such as AODV (Ad-hoc On-demand Distance Vector routing) are commonly used routing algorithms in WSNs and use route discovery broadcast packet to establish route or recover from link failure. However, frequent route discovery can aggravate the congested network. Retransmission technique has been proposed in Not So Tiny (NST) AODV to reduce the number of route discoveries due to short sporadic link failure at the cost of memory consumption and packet delay. To address these issues, we propose a distributed Multi-mode Routing Protocol (MRP) that automatically switches between routing protocols (AODV and NST-AODV) in real time. Incorporating a timing-based route selection mechanism has reduced the numbers of routing packets generated. Results from extensive simulations have shown significant improvement on packet delivery ratio and power consumption with MRP.

  • 52.
    Lim, TiongHoo
    et al.
    University of York.
    Lau, HuiKeng
    Sabah University of Malaysia.
    Timmis, Jon
    University of York.
    Bate, Iain
    University of York.
    Immune-Inspired self healing in wireless sensor networks2012In: Artificial Immune Systems: 11th International Conference, ICARIS 2012, Taormina, Italy, August 28-31, 2012. Proceedings, Springer Berlin/Heidelberg, 2012, p. 42-56Chapter in book (Other academic)
  • 53.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Kraft, Johan
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    A statistical approach to simulation model validation in response-time analysis of complex real-time embedded systems2011In: Proceedings of the ACM Symposium on Applied Computing 2011, 2011, p. 711-716Conference paper (Refereed)
    Abstract [en]

    As simulation-based analysis methods make few restrictions on the system design and scale to very large and complex systems, they are widely used in, e.g., timing analysis of complex real-time embedded systems (CRTES) in industrial circles. However, before such methods are used, the analysis simulation models have to be validated in order to assess if they represent the actual system or not, which also matters to the confidence in the simulation results. This paper presents a statistical approach to validation of temporal simulation models extracted from CRTES, by introducing existing mature statistical hypothesis tests to the context. Moreover, our evaluation using simulation models depicting a fictive but representative industrial robotic control system indicates that the proposed method can successfully identify temporal differences between different simulation models, hence it has the potential to be considered as an effective simulation model validation technique. © 2011 ACM.

  • 54.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    Cucu-Grosjean, Liliana
    INRIA Nancy-Grand Est, Nancy, France.
    A New Way about using Statistical Analysis of Worst-Case Execution Times2011In: ACM SIGBED Review, ISSN 1551-3688, Vol. 8, no 3, p. 11-14Article in journal (Refereed)
    Abstract [en]

    In this paper, we revisit the problem of using Extreme Value Theory (EVT) in the Worst-Case Execution Time (WCET) analysis of the programs running on a single processor. Our proposed statistical WCET analysis method consists of a novel sampling mechanism tackling with some problems that hindered the application of using EVT in the context, and a statistical inference about computation of a WCET estimate of the target program. To be specific, the presented sampling mechanism takes analysis samples from the target program based around end-to-end measurements. Next, the statistical inference using EVT together with other statistical techniques, analyzes such timing traces which contain the execution time data of the program, to compute a WCET estimate with a certain predictable probability of being exceeded.

  • 55.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    Cucu-Grosjean, Liliana
    INRIA Nancy-Grand Est.
    A statistical response-time analysis of complex real-time embedded systems by using timing traces2011In: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings, 2011, p. 43-46Conference paper (Refereed)
    Abstract [en]

    Real-time embedded systems are becoming ever more complex, and we are reaching the stage where even if static Response-Time Analysis (RTA) was feasible from a cost and technical perspective, the results are overly pessimistic making them less useful to the practitioner. When combined with the fact that most timing analysis tends to be statistical in nature, this suggests there should be a move towardstatistical RTA. However, to make such analysis useful, it is imperative that we have evidence that the statistical RTA and the information analyzed is sufficiently accurate. In this paper we present and validatea technique for statistical RTA that can cope with systems that are complex from both a size and tasks' dependencies perspective. This claim is backed up by our evaluation using information from realindustrial control systems.

  • 56.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering.
    Cucu-Grosjean, Liliana
    INRIA Nancy-Grand Est.
    A statistical response-time analysis of real-time embedded systems2012In: Proceedings - Real-Time Systems Symposium, 2012, 2012, p. 351-362Conference paper (Refereed)
    Abstract [en]

    Real-time embedded systems are becoming ever more complex. We are reaching the stage where even if static Response-Time Analysis (RTA) was feasible from a cost and technical perspective, the results of such an analysis are overly pessimistic. This makes them less useful to the practitioner. In addition, the temporal validation and verification of such systems in some applications, e.g., aeronautics, requires the probability of obtaining a worst-case response time larger than a given value in order to support dependable system functions. All these facts advocate moving toward statistical RTA, which instead of calculating absolute worst-case timing guarantees, computes a probabilistic worst-case response time estimate. The contribution of this paper is to present and evaluate such a statistical RTA technique which uses a black box view of the systems under analysis, by not requiring estimates of parameters such as worst-case execution times of tasks. Furthermore, our analysis is applicable to real systems that are complex, e.g., from a task dependencies perspective.

  • 57.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    Cucu-Grosjean, Liliana
    INRIA Nancy-Grand Est, Nancy, France.
    A Trace-Based Statistical Worst-Case Execution Time Analysis of Component-Based Real-Time Embedded Systems2011In: 2011 IEEE 16TH CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA) / [ed] Mammeri, Z., New York: IEEE , 2011Conference paper (Refereed)
    Abstract [en]

    This paper describes the tool support for a framework for performing statistical WCET analysis of real-time embedded systems by using bootstrapping sampling and Extreme Value Theory (EVT). To be specific, bootstrapping sampling is used to generate timing traces, which not only fulfill the requirements given by statistics and probability theory, but also are robust to use in the context of estimating the WCET of programs. Next, our proposed statistical inference uses EVT to analyze such timing traces, and computes a WCET estimate of the target program, pertaining to a given predictable probability. The evaluation results show that our proposed method could have the potential of being able to provide a tighter upper bound on the WCET estimate of the programs under analysis, when compared to the estimates given by the referenced WCET analysis methods.

  • 58.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    Kraft, Johan
    Mälardalen University, School of Innovation, Design and Engineering.
    Norström, Christer
    Mälardalen University, School of Innovation, Design and Engineering.
    Assessment of trace-differences in timing analysis for Complex Real-Time Embedded Systems2011In: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings, 2011, p. 284-293Conference paper (Refereed)
    Abstract [en]

    In this paper, we look at identifying temporal differences between different versions of Complex Real-Time Embedded Systems (CRTES) by using timing traces representing response times and executiontimes of tasks. In particular, we are interested in being able to reason about whether a particular change to CRTES will impact on their temporal performance, which is difficult to answer due to the complicatedtiming behavior such CRTES have. To be specific, we first propose a sampling mechanism to eliminate dependencies existing in tasks' response time and execution time data in the traces taken from CRTES, which makes any statistical inference in probability theory and statistics realistic. Next, we use a mature statistical method, i.e., the non-parametric two-sample Kolmogorov-Smirnov test, to assess the possible temporal differences between different versions of CRTES by using timing traces. Moreover, we introduce a method of reducing the number of samples used in the analysis, while keeping the accuracy ofanalysis results. This is not trivial, as collecting a large amount of samples in terms of executing real systems is often costly. Our evaluation using simulation models describing an industrial robotic controlsystem with complicated tasks' timing behavior, indicates that the proposed method can successfully identify temporal differences between different versions of CRTES, if there is any. Furthermore, our proposed method outperforms the other statistical methods, e.g., bootstrap and permutation tests, that are often widely used in contexts, in terms of bearing on the accuracy of results when other methods have failed.

  • 59.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering.
    Norström, Christer
    Mälardalen University, School of Innovation, Design and Engineering.
    Timing Analyzing for Systems with Execution Dependencies between Tasks2010In: Proceedings of the ACM Symposium on Applied Computing 201, 2010, p. 357-358Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel approach to timing analysis of complex real-time systems with intricate execution dependencies between tasks, such as asynchronous message-passing and globally shared state variables, is presented. By applying the method to a model taken from a real robotic control system, we show the benefit, in terms of reduced pessimism, when compared to a combination of standard static WCET analysis and Response-Time Analysis.

  • 60.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Bate, Iain
    University of York.
    Norström, Christer
    Mälardalen University, School of Innovation, Design and Engineering.
    Timing analyzing for systems with task execution dependencies2010In: Proceedings - International Computer Software and Applications Conference, 2010, p. 515-524Conference paper (Refereed)
    Abstract [en]

    This paper presents a novel approach to timing analysis of complex real-time systems containing data-driven tasks with intricate executiondependencies. Using a system model inspired by industrial control systems, we show how the execution time of tasks can be represented as a mathematical expression instead of a single numeric value. Next, based on this more detailed modeling, we introduce a concrete process of formally obtaining the exact value of both Worst-Case Execution-Time (WCET) and Worst-Case Response-Time (WCRT) of tasks by using upper-part binary search and TIMES (a timed model checker). Finally, in order to show the potential of the proposed approach, we apply it to a model created from a real robotic control system for which the traditional way of obtaining a WCET estimate (through static WCET analysis) on tasks for usage in basic RTA is not appropriate. Our results indicate a significant reduction of pessimism when compared to basic RTA using WCET estimates on tasks given by a basic assumption.

  • 61.
    Lu, Yue
    et al.
    Mälardalen University, School of Innovation, Design and Engineering. INRIA Nancy-Grand Est, Nancy, France.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Cucu-Grosjean, Liliana
    INRIA Nancy-Grand Est, Nancy, France.
    Bate, Iain
    University of York, York, United Kingdom.
    RapidRT: A Tool For Statistical Response-Time Analysis of Complex Industrial Real-Time Embedded Systems2011Conference paper (Refereed)
    Abstract [en]

    RapidRT is a tool for statistical response time analysis of Complex Industrial Real-Time Embedded Systems (CIRTES). A key feature of this tool is that it does not require worst-case execution times of tasks to be known for the computation of a probabilistic task worst-case response time estimate. The presented tool is a step towards bridging the gap between academic research and industrial practice.

  • 62.
    Malekzadeh, Mahnaz
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. University of York, York, UK.
    Improving the Stop-Test Decision When Testing Data are Slow to Converge2016Report (Other academic)
    Abstract [en]

    Testing of safety-critical systems is an important and costly endeavor. To date work has been mainly focusing on the design and application of diverse testing strategies. However, they have left the important decision of “when to stop testing” as an open research issue. In our previous work, we proposed a convergence algorithm that informs the tester when it is concluded that testing for longer will not reveal sufficiently important new findings, hence, should be stopped. The stoptest decision proposed by the algorithm was in the context of testing the worst-case timing characteristics of a system and was evaluated based on the As Low As Reasonably Practicable (ALARP) principle. The ALARP principle is an underpinning concept in many safety standards which is a cost-benefit argument. ALARP implies that a tolerable risk should be reduced to a point at which further risk-reduction is grossly disproportionate compared to the benefit attained. An ALARP stop-test decision means that the cost associated with further testing, after the algorithm stops, does not justify the benefit, i.e., any further increased in the observed worst-case timing.

    In order to make a stop-test decision, the convergence algorithm used the Kullback-Leibler DIVergence (KL DIV) statistical test and was shown to be successful while being applied on system’s tasks having similar characteristics. However, there were some experiments in which the stop-test decision did not comply to the ALARP principle, i.e., it stopped sooner than expected by the ALARP criteria. Therefore, in this paper, we investigate whether the performance of the algorithm could be improved in such experiments focusing on the KL DIV test. More specifically, we firstly determine which features of KL DIV could adversely affect the algorithm performance. Secondly, we investigate whether another statistical test, i.e., the Earth Mover’s Distance (EMD), could potentially cover weaknesses of KL DIV. Finally, we experimentally evaluate our hypothesis of whether EMD does improve the algorithm where KL DIV has shown to not perform as expected.

  • 63.
    Malekzadeh, Mahnaz
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. University of York, York, UK.
    Influential Nuisance Factors on a Decision of Sufficient Testing2015In: Algorithms and Architectures for Parallel Processing: ICA3PP International Workshops and Symposiums, Zhangjiajie, China, November 18–20, 2015, Proceedings, 2015, p. 819-828Conference paper (Refereed)
    Abstract [en]

    Testing of safety-critical embedded systems is an important and costly endeavor. To date work has been mainly focusing on the design and application of diverse testing strategies. However, they have left an open research issue of when to stop testing a system. In our previous work, we proposed a convergence algorithm that informs the tester when the current testing strategy does not seem to be revealing new insight into the worst-case timing properties of system tasks, hence, should be stopped. This algorithm was shown to be successful while being applied across task sets having similar characteristics. For the convergence algorithm to become robust, it is important that it holds even if the task set characteristics here called nuisance factors, vary. Generally speaking, there might be either the main factors under analysis, called design factors, or nuisance factors that influence the performance of a process or system. Nuisance factors are not typically of interest in the context of the analysis. However, they vary from system to system and may have large effects on the performance, hence, being very important to be accounted for. Consequently, the current paper looks into a set of nuisance factors that affect our proposed convergence algorithm performance. More specifically, it is interested in situations when the convergence algorithm performance significantly degrades influencing its reliability. The work systematically analyzes each nuisance factor effect using a well-known statistical method, further, derives the most influential factors.

  • 64.
    Malekzadeh, Mahnaz
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Making an ALARP Decision of Sufficient Testing2014In: Proceedings - 2014 IEEE 15th International Symposium on High-Assurance Systems Engineering, HASE 2014, Miami, United States, 2014, p. 57-64Conference paper (Refereed)
    Abstract [en]

    ALARP is an important concept in many safety standards. It helps in making a decision about how tolerable a risk is. A tolerable risk should be reduced to a point that is As Low As Reasonably Practicable (ALARP) which implies further risk-reduction is grossly inappropriate compared to the benefit attained. To date work has considered the process, safety arguments, and influencing factors of how to make an ALARP decision but not shown how to make a quantified judgement for it. In this paper a method for making an ALARP judgement decision is proposed in the context of testing the worst-case timing properties of systems. The method is based around a convergence algorithm that informs the tester when it is believed that testing for longer will not reveal sufficiently important new findings, i.e. any significant increase in observed worst-case timing needs a disproportionate amount of testing time.

  • 65.
    Malekzadeh, Mahnaz
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. University of York, York, UK.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Using Design of Experiments to Optimise a Decision of Sufficient Testing2015In: The 41st Euromicro Conference on Software Engineering and Advanced Applications SEAA'15, 2015, p. 53-60Conference paper (Refereed)
    Abstract [en]

    Testing of safety-critical embedded systems is an important and costly endeavor. To date researchers and practitioners have been mainly focusing on the design and application of diverse testing strategies, but leaving the test stopping criteria as an ad hoc decision and an open research issue. In our previous work, we proposed a convergence algorithm that informs the tester when the current testing strategy does not seem to be revealing new insight into the worst-case timing properties of tasks and hence should be stopped. This algorithm was shown to be successful but its trial and error tuning of parameters was an issue. In this paper, we use the Design of Experiment (DOE) approach to optimise the algorithm's performance and to improve its scalability. During our experimental evaluations the optimised algorithm showed improved performance by achieving relatively the same results with 42% less testing cost as compared to our previous work. The algorithm also has better scalability and opens up a new path towards achieving cost effective non-functional testing of real-time embedded systems.

  • 66.
    Pölzbauer, Florian
    et al.
    Virtual Vehicle, Graz, Austria.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering.
    Brenner, Eugen
    Graz University of Technology.
    On Extensible Networks for Embedded Systems2013In: Proceedings of the International Symposium and Workshop on Engineering of Computer Based Systems, 2013, p. 69-77Conference paper (Refereed)
    Abstract [en]

    When designing a distributed computing-system, the communication networks are a key determining factor for system's performance. A common approach is to minimize bandwidth-consumption, while other important objectives - maintainability, extensibility, robustness - get less attention in the literature. In this work we provide a design-methodology how to efficiently balance these conflicting objectives. We build an initial network configuration by applying heuristics. Then, we refine this configuration by using optimization strategies which address the multi-objective optimization problem. By doing so, the network configuration not only satisfies the requirements of the current communication-demand, but it is also prepared to handle additional future communication-demand. Experimental results from an automotive case-study show that extensibility can be significantly improved (up to 44%) while trading only a little bandwidth-efficency (1% deteriation).

  • 67.
    Pölzlbauer, Florian
    et al.
    Virtual Vehicle, Graz.
    Bate, Iain
    University of York.
    Brenner, Eugen
    Graz University of Technology.
    Efficient constraint handling during designing reliable automotive real-time systems2012In: Reliable Software Technologies–Ada-Europe 2012: Lecture Notes in Computer Science Volume 7308, Springer Berlin/Heidelberg, 2012, p. 207-220Chapter in book (Other academic)
    Abstract [en]

    In modern embedded systems, e.g. avionics and automotive, it is not unusual for there to be between 40 and 100 processors with a great deal of the software having hard real-time requirements and constraints over how, when and where they execute. The requirements and constraints are essential to the overall systems dependability and safety (e.g. to ensure replicas execute on different hardware). This leads to a complex design space exploration (DSE) problem which cannot be practically solved manually especially if the schedule is to be maintained.

    In this paper it is shown that dealing with the constraints using a conventional state of the art “System Configuration Algorithm” is less efficient, less effective and does not scale well. This issue can be improved by performing constraint pre-processing as well as constraint encoding. It is shown that our approach can handle typical industrial requirements that come from the automotive industry’s AUTOSAR standard in an efficient way.

  • 68.
    Pölzlbauer, Florian
    et al.
    Virtual Vehicle, Graz.
    Bate, Iain
    University of York.
    Brenner, Eugen
    Graz University of Technology.
    Optimised Frame Packing for Embedded Systems2012In: Embedded Systems Letters, ISSN 1943-0663, Vol. 4, no 3, p. 65-68Article in journal (Refereed)
    Abstract [en]

    During system synthesis (i.e., task allocation) the transmission of messages between tasks is usually addressed in a simplistic way. If a message is exchanged via an external bus, it is assumed each message is packed in an individual frame. This assumption leads to an overestimation of bus bandwidth demand and frameresponse time. For some systems (i.e., automotive), this pessimism is not acceptable and therefore frame packing is often performed where multiple messages are packed into a single frame. In this paper, an improved frame packing approach is provided.

  • 69.
    Pölzlbauer, Florian
    et al.
    Virtual Vehicle, Graz.
    Bate, Iain
    Department of Computer Science, University of York, York, UK.
    Brenner, Eugen
    Graz University of Technology.
    Software Deployment for Distributed Embedded Real-Time Systems of Automotive Applications2014In: Embedded and Real Time System Development: A Software Engineering Perspective / [ed] Mohammad Ayoub Khan et. al., Springer Berlin/Heidelberg, 2014, p. 305-328Chapter in book (Other academic)
    Abstract [en]

    Automotive applications can be described as distributed embedded software which perform real-time computation on top of a heterogeneous hardware platform. One key phase in designing distributed software systems is software deployment. Therein it is decided how software components are deployed over the hardware platform, and how the communication between software components is performed. These decisions significantly determine the system performance. This chapter tackles the software deployment problem, tailored to the needs of the automotive domain. Thereby, the focus is on two issues: the configuration of the communication infrastructure and how to handle design constraints. It is shown, how state-of-the-art approaches have to be extended in order to tackle these issues, and how the overall process can be performed efficiently, by utilizing search methodologies.

  • 70.
    Rodriguez-Navas, Guillermo
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Graydon, Patrick
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Dept. of Computer Science, University of York, United Kingdom.
    From fault injection to mutant injection: The next step for safety analysis?2013In: Lect. Notes Comput. Sci., 2013, p. 276-277Conference paper (Refereed)
    Abstract [en]

    Mutation testing has been used to assess test suite coverage, and researchers have proposed adapting the idea for other uses. Safety kernels allow the use of untrusted software components in safety-critical applications: a trusted software safety kernel detects undesired behavior and takes remedial action. We propose to use specification mutation, model checking, and model-based testing to verify safety kernels for component-based, safety-critical computer systems.

  • 71.
    Sljivo, Irfan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Jaradat, Omar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bate, Iain
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Graydon, Patrick
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Deriving Safety Contracts to Support Architecture Design of Safety Critical Systems2015In: Proceedings of IEEE International Symposium on High Assurance Systems Engineering, 2015, Vol. january, p. 126-133Conference paper (Refereed)
    Abstract [en]

    The use of contracts to enhance the maintainability of safety-critical systems has received a significant amount of research effort in recent years. However some key issues have been identified: the difficulty in dealing with the wide range of properties of systems and deriving contracts to capture those properties; and the challenge of dealing with the inevitable incompleteness of the contracts. In this paper, we explore how the derivation of contracts can be performed based on the results of failure analysis. We use the concept of safety kernels to alleviate the issues. Firstly the safety kernel means that the properties of the system that we may wish to manage can be dealt with at a more abstract level, reducing the challenges of representation and completeness of the “safety” contracts. Secondly the set of safety contracts is reduced so it is possible to reason about their satisfaction in a more rigorous manner.

  • 72.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    A feedback-driven timing synchronisation protocol for cellular sensornets2010In: 2010 IEEE 7th International Conference on Mobile Adhoc and Sensor Systems, MASS 2010, 2010, p. 482-491Conference paper (Refereed)
    Abstract [en]

    Interaction between sensornet nodes and the physical environment in which they are embedded implies realtime requirements. Application tasks must be executed in the correct place, and in the correct order, for correct application behaviour. Sensornets generally have no global clock, and incur unacceptable cost if traditional synchronisation protocols are implemented. We present a lightweight primitive which generates a periodic sequence of synchronisation events which are coordinated across large sensornets structured into clusters or cells. Two biologically-inspired mechanisms are combined; desynchronisation within cells, and synchronisation between cells. This hierarchical coordination provides a global basis for local application-driven timing decisions at each node

  • 73.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    An improved lightweight synchronisation primitive for sensornets2009In: 2009 IEEE 6th International Conference on Mobile Adhoc and Sensor Systems, MASS '09, 2009, p. 448-457Conference paper (Refereed)
    Abstract [en]

    Sensornets must allocate limited computation and energy resources efficiently to maximise utility and lifetime. This task is complicated by the need to coordinate activity between nodes as sensornets are necessarily real-time collaborative systems. In this paper we present and evaluate lightweightadaptive protocols based on pulse-coupled oscillators to synchronise tasks within a unicellular sensornet. A near-optimal schedule is constructed and dynamically maintained under non-ideal network conditions.

  • 74.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Do Sensornet Protocol Variants Yield Real Benefits?2010Conference paper (Refereed)
    Abstract [en]

    Simple, stateless networking protocols provide a low-cost and predictable foundation upon which to build decentralised applications. Sensornets are complex, containing emergent behaviour; identifying protocols offering appropriate behaviour may be difficult. In this paper we evaluate the relative performance of gossiping protocol variants in non-ideal sensornets. We examine the extent to which a "standard" gossiping protocol might be outperformed by variants of this standard, each specialised and optimised to mitigate anticipated problems. We categorise and measure the undesired behaviours that remain, as a foundation for future protocols which will address these specific issues.

  • 75.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Energy efficient duty allocation protocols for wireless sensor networks2009In: Proceedings of the IEEE International Conference on Engineering of Complex Computer Systems, ICECCS, 2009, p. 58-67Conference paper (Refereed)
    Abstract [en]

    Wireless sensor networks require shared medium access management to prevent collisions, message corruption and other unhelpful effects. Cellular sensor-nets require minimal energy consumption to maximise network lifetime, and management of interaction with base stations and other cells. We present a protocol which dynamically generates a near-optimal duty schedule within a cell such that communication duty is shared evenly between participating nodes with exactly one node on-duty at any given time.

  • 76.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    LIPS: A Protocol Suite for Homeostatic Sensornet Management2011In: Proceedings - 2011 16th IEEE International Conference on Engineering of Complex Computer Systems, ICECCS 2011, 2011, p. 263-272Conference paper (Refereed)
    Abstract [en]

    Sensornets are often deployed into inaccessible, dangerous, or changeable physical environments. Centralised control and management is generally infeasi-ble. Autonomous, self-configuring, and self-managing mechanisms are required to provide a suitable infrastructure which reliably supports distributed applications, hiding any underlying instability. The Lightweight Integrated Protocol Suite (LIPS) coordinates time-sensitive activity, and regulates network size and density, in self-managing cellular sensornets. Although components can be implemented in isolation, each contributes part of a larger, integrated solution.

  • 77.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Maintaining stable node populations in long-lifetime sensornets2010In: Proceedings of the IEEE International Conference on Engineering of Complex Computer Systems, ICECCS, 2010, p. 159-168Conference paper (Refereed)
    Abstract [en]

    Sensornets provide coverage of physical phenomena over extended periods, perhaps months or years. However, active nodes may deplete finite batteries within days, and are prone to failure. The sensornet application may require a given number of active nodes within each region to provide appropriate sensor redundancy and processing capacity. If many nodes are deployed, at any given time a smaller working set of the correct size can be selected for duty. In this paper we present a lightweight approach to active population management. An omniscient overview of network state is not required, and expensive communication activity is minimised. Probabilistic methods are employed, ensuring that individual nodes can make appropriate decisions using only locally available information.

  • 78.
    Tate, Jonathan
    et al.
    University of York, UK.
    Bate, Iain
    University of York, UK.
    Probabilistic Methods For Dynamic Node Population Management In Sensornets2009Other (Refereed)
  • 79.
    Tate, Jonathan
    et al.
    University of York, UK.
    Bate, Iain
    University of York, UK.
    Routing In Cellular Sensornets With Uniquely Identified Destination Nodes2010Other (Refereed)
  • 80.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Sensornet protocol tuning using principled engineering methods2010In: The Computer Journal, ISSN 0010-4620, Vol. 53, no 7, p. 991-1019Article in journal (Refereed)
    Abstract [en]

    Sensornet designers seek to maximize energy efficiency while maintaining acceptable Quality of Service. However, the interactions between multiple tunable protocol parameters and multiple performance metrics are generally complex and unknown, and combinatorial explosion renders impossible any exhaustive search approach. Most work published to date employs seemingly arbitrary choices of protocol parameters, derived by informal judgement and limited trial and error experiments. This lack of rigour may lead to sub-optimal parameter selection and sub-optimal network behaviour, and may mask the real performance differences of dissimilar protocols. We describe a reusable engineering method to address this multi-dimensional optimization problem, based on sound engineering principles widely recognized and applied beyond Computer Science. We provide a mechanism with which to de-risk deployment of sensornets tuned within training environments, and evaluate the robustness of these tunings to changing environments. The mechanism is also useful for comparative evaluation of protocols within a fixed deployment context. © The Author 2009. Published by Oxford University Press on behalf of The British Computer Society.

  • 81.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Synchronising timing signals in cellular sensornets using a hybrid algorithm2009Report (Refereed)
  • 82.
    Tate, Jonathan
    et al.
    University of York.
    Bate, Iain
    University of York.
    Tuning complex sensornet systems using principled engineering methods2009In: Proceedings of the International Symposium and Workshop on Engineering of Computer Based Systems, 2009, p. 275-284Conference paper (Refereed)
    Abstract [en]

    Sensornet lifespan and utility is limited by the energy resources of individual motes. Network designers seek to maximise energy efficiency while maintaining acceptable Quality of Service. However; the interactions between multiple tunable protocol parameters and multiple performance metrics are generally complex and unknown, and combinatorial explosion renders impossible any exhaustive search approach. In this paper we describe an engineering method to address this multi-dimensional optimisation problem. We apply a Design Of Experiments approach to sample the entire search space. Statistical models are fitted to experimental results to define relationships between inputs and outputs, and to obtain near-optimal solutions.

  • 83.
    Tate, Jonathan
    et al.
    University of York, UK.
    Bate, Iain
    University of York, UK.
    Understanding behavioural tradeoffs in large-scale sensornet design2009Conference paper (Refereed)
  • 84.
    Tate, Jonathan
    et al.
    University of York, UK.
    Bate, Iain
    University of York, UK.
    YASS: a Scaleable Sensornet Simulator for Large Scale Experimentation.2008In: CPA, IOS Press, 2008, p. 411-430Conference paper (Refereed)
  • 85.
    Tate, Jonathan
    et al.
    University of York, UK.
    Bate, Iain
    University of York, UK.
    Poulding, Simon
    University of York, UK.
    Tuning protocols to improve the energy efficiency of sensornets2008Conference paper (Refereed)
  • 86.
    Tate, Jonathan
    et al.
    University of York.
    Woolford-Lim, Benjamin
    University of Birmingham.
    Bate, Iain
    University of York.
    Yao, Xin
    University of Birmingham.
    Comparing design of experiments and evolutionary approaches to multi-objective optimisation of sensornet protocols2009In: 2009 IEEE Congress on Evolutionary Computation, CEC 2009, 2009, p. 1137-1144Conference paper (Refereed)
    Abstract [en]

    The lifespan, and hence utility, of sensornets is limited by the energy resources of individual motes. Network designers seek to maximise energy efficiency while maintaining an acceptable network Quality of Service. However, the interactions between multiple tunable protocol parameters and multiple sensornet performance metrics are generally complex and unknown. In this paper we address this multi-dimensional optimisation problem by two distinct approaches. Firstly, we apply a Design Of Experiments approach to obtain a generalised linear interaction model, and from this derive an estimated near-optimal solution. Secondly, we apply the Two-Archive evolutionary algorithm to improve solution quality for a specific problem instance. We demonstrate that, whereas the first approach yields a more generally applicable solution, the second approach yields a broader range of viable solutions at potentially lower experimental cost.

  • 87.
    Tate, Jonathan
    et al.
    University of York.
    Woolford-Lim, Benjamin
    University of Birmingham.
    Bate, Iain
    University of York.
    Yao, Xin
    University of Birmingham.
    Evolutionary and principled search strategies for sensornet protocol optimization2012In: IEEE transactions on systems, man and cybernetics. Part B. Cybernetics, ISSN 1083-4419, E-ISSN 1941-0492, Vol. 42, no 1, p. 163-180Article in journal (Refereed)
    Abstract [en]

    Interactions between multiple tunable protocol parameters and multiple performance metrics are generally complex and unknown; finding optimal solutions is generally difficult. However, protocol tuning can yield significant gains in energy efficiency and resource requirements, which is of particular importance for sensornetsystems in which resource availability is severely restricted. We address this multi-objective optimization problem for two dissimilar routing protocols and by two distinct approaches. First, we apply factorial design and statistical model fitting methods to reject insignificant factors and locate regions of the problem space containing near-optimal solutions by principled search. Second, we apply the Strength Pareto Evolutionary Algorithm 2 and Two-Archive evolutionary algorithms to explore the problem space, with each iteration potentially yielding solutions of higher quality and diversity than the preceding iteration. Whereas a principledsearch methodology yields a generally applicable survey of the problem space and enables performance prediction, the evolutionary approach yields viable solutions of higher quality and at lower experimental cost. This is the first study in which sensornet protocol optimization has been explicitly formulated as a multi-objective problem and solved with state-of-the-art multi-objective evolutionary algorithms.

  • 88.
    Tovar, Eduardo
    et al.
    Polytechnic Institute of Porto.
    Viana, Júlio C
    Critical Materials S.A..
    Pereira, Nuno
    Polytechnic Institute of Porto.
    Philipp, François
    Technische Universität Darmstadt.
    Bate, Iain
    University of York.
    Mayer, Dirk
    Fraunhofer LBF.
    Indrusiak, Leandro Soares
    University of York.
    Heras, José
    ADVANTIC Sistemas y Servicios S.L..
    Penna, Sérgio
    Embraer, São José dos Campos.
    Pacheco, Filipe
    Polytechnic Institute of Porto.
    Loureiro, João
    Polytechnic Institute of Porto.
    Negrão, José
    Embraer, São José dos Campos.
    Networked Embedded Systems for Active Flow Control in Aircraft2012Report (Refereed)
    Abstract [en]

    Abstract— Aerodynamic drag is known to be one of the factorscontributing more to increased aircraft fuelconsumption. Theprimary source of skin friction drag during flight is theboundary layer separation. This is the layer ofair movingsmoothly in the immediate vicinity of the aircraft. In this paperwe discuss a cyber-physical system approachable ofperforming an efficient suppression of the turbulent flow byusing a dense sensing deployment to detect the lowpressureregion and a similarly dense deployment of actuators tomanage the turbulent flow. With this concept, onlytheactuators in the vicinity of a separation layer are activated,minimizing power consumption and also the induced drag.

  • 89.
    Wheeler, Sitsofe
    et al.
    University of York.
    Bate, Iain
    University of York.
    Bartlett, Mark
    University of York.
    Video subset selection for measurement based Worst Case Execution Time analysis2011In: SIES 2011 - 6th IEEE International Symposium on Industrial Embedded Systems, Conference Proceedings, 2011, p. 213-222Conference paper (Refereed)
    Abstract [en]

    Worst Case Execution Time (WCET) has traditionally approached problems with small, well defined input spaces. For processes with a large input space (such as video) existing techniques struggle to produce a meaningful result. This work investigates a technique that reduces the input space while still preserving execution time properties to allow subsequent WCET analysis to be more effective.

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