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Afshar, Sara ZargariORCID iD iconorcid.org/0000-0002-0474-2904
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Publications (10 of 26) Show all publications
Balasubramanian, S., Afshar, S. Z., Behnam, M., Gai, P. & Bril, R. J. (2017). A dual shared stack for FSLM in Erika enterprise. In: The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17: . Paper presented at The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17, 14 Aug 2017, Hsinchu, Taiwan.
Open this publication in new window or tab >>A dual shared stack for FSLM in Erika enterprise
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2017 (English)In: The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17, 2017Conference paper, Published paper (Refereed)
Abstract [en]

Recently, the flexible spin-lock model (FSLM) has been introduced, unifying spin-based and suspension-based resource sharing protocols for real-time multi-core platforms. Unlike the multiprocessor stack resource policy (MSRP), FSLM doesn’t allow tasks on a core to share a single stack, however. In this paper, we present a hypothesis claiming that for a restricted range of spin-lock priorities, FSLM requires only two stacks. We briefly describe our implementation of a dual stack for FSLM in the Erika Enterprise RTOS as instantiated on an Altera Nios II platform using 4 soft-core processors.

National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-37056 (URN)
Conference
The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17, 14 Aug 2017, Hsinchu, Taiwan
Projects
PRESS - Predictable Embedded Software SystemsDPAC - Dependable Platforms for Autonomous systems and Control
Available from: 2017-11-07 Created: 2017-11-07 Last updated: 2018-03-05Bibliographically approved
Šljivo, I., Lisova, E. & Afshar, S. (2017). Agent-centred Approach for Assuring Ethics in Dependable Service Systems. In: 13th IEEE World Congress on Services SERVICES 2017: . Paper presented at 13th IEEE World Congress on Services SERVICES 2017, 25 Jun 2017, Honolulu, United States (pp. 51-58). , Article ID 8036721.
Open this publication in new window or tab >>Agent-centred Approach for Assuring Ethics in Dependable Service Systems
2017 (English)In: 13th IEEE World Congress on Services SERVICES 2017, 2017, p. 51-58, article id 8036721Conference paper, Published paper (Refereed)
Abstract [en]

As the world enters the information era, more and more dependable services controlling and even making our decisions are moved to the ubiquitous smart devices. While various standards are in place to impose the societal ethical norms on decision-making of those devices, the rights of the individuals to satisfy their own moral norms are not addressed with the same scrutiny. Hence, the right of the individuals to reason on their own and evaluate morality of certain decisions is at stake, as many decisions are outsourced from the user to the service providers and third party stakeholders without the user's full awareness of all the aspects of those decisions. In this work we propose an agent-centred approach for assuring ethics in dependable technological service systems. We build upon assurance of safety and security and propose the notion of ethics assurance case as a way to assure that individual users have been made aware of all the ethically challenging decisions that might be performed or enabled by the service provider. We propose a framework for identifying and categorising ethically challenging decisions, and documenting the ethics assurance case. We apply the framework on an illustrative example.

National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-35502 (URN)10.1109/SERVICES.2017.18 (DOI)000425960800009 ()2-s2.0-85032373741 (Scopus ID)
Conference
13th IEEE World Congress on Services SERVICES 2017, 25 Jun 2017, Honolulu, United States
Projects
PRESS - Predictable Embedded Software SystemsRetNet - The European Industrial Doctorate Programme on Future Real-Time NetworksFuture factories in the Cloud
Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2018-03-15Bibliographically approved
Afshar, S. Z., Behnam, M., J. Bril, R. & Nolte, T. (2017). An optimal spin-lock priority assignment algorithm for real-time multi-core systems. In: The 23th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA'17: . Paper presented at The 23th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA'17, 16 Aug 2017, Hsinchu, Taiwan. , Article ID 8046310.
Open this publication in new window or tab >>An optimal spin-lock priority assignment algorithm for real-time multi-core systems
2017 (English)In: The 23th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA'17, 2017, article id 8046310Conference paper, Published paper (Refereed)
Abstract [en]

Support for exclusive access to shared (global) resources is instrumental in the context of embedded real-time multi-core systems, and mechanisms for achieving such access must be deterministic and efficient. There exist two traditional approaches for multiprocessors when a task requests a global resource that is locked by a task on a remote core: a spin-based approach, i.e. non-preemptive busy waiting for the resource to become available, and a suspension-based approach, i.e. the task relinquishes the processor. A suspension-based approach can be viewed as a spin-based approach where the lowest priority on a core is used during spinning, similar to a non-preemptive spin-based approach where the highest priority on a core is used. By taking such a view, we previously provided a general model for spinning, where any arbitrary priority can be used for spinning, i.e. from the lowest to the highest priority on a core. Targeting partitioned fixed-priority preemptive scheduled multiprocessors and spin-based approaches that use a fixed priority for spinning per core for all tasks, we aim at increasing the schedulability of multiprocessor systems by using the spin-lock priority per core as parameter. In this paper, we present (i) a generalization of the traditional worst-case response-time analysis for non-preemptive spin-based approaches addressing an arbitrary but fixed spin-lock priority per core, (ii) an optimal spin-lock priority assignment (OSPA) algorithm per core, i.e. an algorithm that will find a fixed spin-lock priority per core that will make the system schedulable, whenever such an assignment exists and, (iii) comparative evaluations of the OSPA algorithm with the spin-based and suspension-based approaches where OSPA showed up to 38% improvement compared to both approaches.

National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-37055 (URN)10.1109/RTCSA.2017.8046310 (DOI)000425851000008 ()2-s2.0-85032735746 (Scopus ID)
Conference
The 23th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA'17, 16 Aug 2017, Hsinchu, Taiwan
Projects
PRESS - Predictable Embedded Software SystemsDPAC - Dependable Platforms for Autonomous systems and Control
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-03-15Bibliographically approved
Balasubramanian, S., Afshar, S. Z., Gai, P., Behnam, M. & J. Bril, R. (2017). Incorporating implementation overheads in the analysis for the flexible spin-lock model. In: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY: . Paper presented at 43rd Annual Conference of the IEEE Industrial Electronics Society IECON 2017, 30 Oct 2017, Beijing, China (pp. 411-8418).
Open this publication in new window or tab >>Incorporating implementation overheads in the analysis for the flexible spin-lock model
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2017 (English)In: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, 2017, p. 411-8418Conference paper, Published paper (Refereed)
Abstract [en]

The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource sharing protocols for partitioned fixed-priority preemptive scheduling based real-time multiprocessor platforms. Recent work has been done in defining the protocol for FSLM and providing a schedulability analysis without accounting for the implementation overheads. In this paper, we extend the analysis for FSLM with implementation overheads. Utilizing an initial implementation of FSLM in the OSEK/VDX-compliant Erika Enterprise RTOS on an Altera Nios II platform using 4 soft-core processors, we present an improved implementation. Given the design of the implementation, the overheads are characterized and incorporated in specific terms of the existing analysis. The paper also supplements the analysis with measurement results, enabling an analytical comparison of FSLM with the natively provided multiprocessor stack resource policy (MSRP), which may serve as a guideline for the choice of FSLM or MSRP for a specific application.

Series
IEEE Industrial Electronics Society
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-37057 (URN)10.1109/IECON.2017.8217477 (DOI)000427164808044 ()2-s2.0-85046623624 (Scopus ID)978-1-5386-1127-2 (ISBN)
Conference
43rd Annual Conference of the IEEE Industrial Electronics Society IECON 2017, 30 Oct 2017, Beijing, China
Projects
PRESS - Predictable Embedded Software SystemsDPAC - Dependable Platforms for Autonomous systems and Control
Available from: 2017-11-07 Created: 2017-11-07 Last updated: 2018-05-24Bibliographically approved
Afshar, S. (2017). Lock-Based Resource Sharing for Real-Time Multiprocessors. (Doctoral dissertation). Västerås: Mälardalen University
Open this publication in new window or tab >>Lock-Based Resource Sharing for Real-Time Multiprocessors
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Embedded systems are widely used in the industry and are typically resource constrained, i.e., resources such as processors, I/O devices, shared buffers or shared memory might be limited in the system. Hence, techniques that can enable an efficient usage of processor bandwidths in such systems are of great importance. Locked-based resource sharing protocols are proposed as a solution to overcome resource limitation by allowing the available resources in the system to be safely shared. In recent years, due to a dramatic enhancement in the functionality of systems, a shift from single-core processors to multi-core processors has become inevitable from an industrial perspective to tackle the raised challenges due to increased system complexity. However, the resource sharing protocols are not fully mature for multi-core processors. The two classical multi-core processor resource sharing protocols, spin-based and suspension-based protocols, although providing mutually exclusive access to resources, can introduce long blocking delays to tasks, which may be unacceptable for many industrial applications. In this thesis we enhance the performance of resource sharing protocols for partitioned scheduling, which is the de-facto scheduling standard for industrial real-time multi-core processor systems such as in AUTOSAR, in terms of timing and memory requirements.

 

A new scheduling approach uses a resource efficient hybrid approach combining both partitioned and global scheduling where the partitioned scheduling is used to schedule the major number of tasks in the system. In such a scheduling approach applications with critical task sets use partitioned scheduling to achieve higher level of predictability. Then the unused bandwidth on each core that is remained from partitioning is used to schedule less critical task sets using global scheduling to achieve higher system utilization. These scheduling schema however lacks a proper resource sharing protocol since the existing protocols designed for partitioned and global scheduling cannot be directly applied due to the complex hybrid structure of these scheduling frameworks. In this thesis we propose a resource sharing solution for such a complex structure. Further, we provide the blocking bounds incurred to tasks under the proposed protocols and enhance the schedulability analysis, which is an essential requirement for real-time systems, with the provided blocking bounds.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2017
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 247
National Category
Embedded Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:mdh:diva-37215 (URN)978-91-7485-361-2 (ISBN)
Public defence
2017-12-19, Kappa, Mälardalens högskola, Västerås, 13:30 (English)
Opponent
Supervisors
Available from: 2017-11-07 Created: 2017-11-06 Last updated: 2018-01-09Bibliographically approved
Hatvani, L., Afshar, S. Z. & J. Bril, R. (2017). Optimal Priority and Threshold Assignment for Fixed-priority Preemption Threshold Scheduling. In: 7th Embedded Operating Systems Workshop EWiLi'17: . Paper presented at 7th Embedded Operating Systems Workshop EWiLi'17, 06 Oct 2017, Seoul, South Korea.
Open this publication in new window or tab >>Optimal Priority and Threshold Assignment for Fixed-priority Preemption Threshold Scheduling
2017 (English)In: 7th Embedded Operating Systems Workshop EWiLi'17, 2017Conference paper, Published paper (Refereed)
National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-37058 (URN)
Conference
7th Embedded Operating Systems Workshop EWiLi'17, 06 Oct 2017, Seoul, South Korea
Projects
PRESS - Predictable Embedded Software Systems
Available from: 2017-11-07 Created: 2017-11-07 Last updated: 2018-03-05Bibliographically approved
Afshar, S., Behnam, M., J. Bril, R. & Nolte, T. (2017). Per Processor Spin-Lock Priority for Partitioned Multiprocessor Real-Time Systems. Leibniz Transactions on Embedded Systems (2)
Open this publication in new window or tab >>Per Processor Spin-Lock Priority for Partitioned Multiprocessor Real-Time Systems
2017 (English)In: Leibniz Transactions on Embedded Systems, ISSN 2199-2002, no 2Article in journal (Other academic) Published
Abstract [en]

Two traditional approaches exist for a task that is blocked on a global resource; a task either performs a non-preemptive busy wait, i.e., spins, or suspends and releases the processor. Previously, we have shown that both approaches can be viewed as spinning either at the highest priority HP or at the lowest priority on the processor LP, respectively. Based on this view, previously we have generalized a task's blocking behavioral model, as spinning at any arbitrary priority level. In this paper, we focus on a particular class of spin-lock protocols from the introduced flexible spin-lock model where spinning is performed at a priority equal to or higher than the highest local ceiling of the global resources accessed on a processor referred to as CP spin-lock approach. In this paper, we assume that all tasks of a specific processor are spinning on the same priority level. Given this class and assumption, we show that there exists a spin-lock protocol in this range that dominates the classic spin-lock protocol which tasks spin on highest priority level (HP). However we show that this new approach is incomparable with the CP spin-lock approach. Moreover, we show that there may exist an intermediate spin-lock approach between the priority used by CP spin-lock approach and the new introduced spin-lock approach that can make a task set schedulable when those two cannot. We provide an extensive evaluation results comparing the HP, CP and the new proposed approach.

National Category
Computer Sciences
Identifiers
urn:nbn:se:mdh:diva-37183 (URN)10.4230/LITES-v004-i002-a003 (DOI)
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2018-12-14Bibliographically approved
Afshar, S., Khalilzad, N., Behnam, M., Bril, R. J. & Nolte, T. (2016). Intra-component Resource Sharing on a Virtual Multiprocessor Platform. In: ACM SIGBED Review: Special Issue on 8th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems. Paper presented at 8th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems CRTS'15, 01 Dec 2015, San Antonio, United States (pp. 31-32).
Open this publication in new window or tab >>Intra-component Resource Sharing on a Virtual Multiprocessor Platform
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2016 (English)In: ACM SIGBED Review: Special Issue on 8th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems, 2016, p. 31-32Conference paper, Published paper (Refereed)
Abstract [en]

Component-based software development facilitates the development process of large and complex software systems. By the advent of multiprocessors, the independently developed components can be integrated on a multi-core platform to achieve an efficient use of system hardware and a decrease in system power consumption and costs. In this paper, we consider a virtual multiprocessor platform where each component can be dynamically allocated to any set of processors of the platform with a maximum concurrency level. Global-EDF is used for intra-component scheduling. The existing analysis for such systems have assumed that tasks are independent. In this paper, we enable intra-component resource sharing for this platform. We investigate using a spin-based resource sharing protocol with the accompanying analysis that extends the existing analysis for independent tasks. We briefly illustrate and evaluate our initial results with an example.

National Category
Computer Systems
Identifiers
urn:nbn:se:mdh:diva-32777 (URN)10.1145/2983185.2983190 (DOI)
External cooperation:
Conference
8th International Workshop on Compositional Theory and Technology for Real-Time Embedded Systems CRTS'15, 01 Dec 2015, San Antonio, United States
Projects
PRESS - Predictable Embedded Software Systems
Available from: 2016-09-01 Created: 2016-08-24 Last updated: 2016-09-01Bibliographically approved
Afshar, S., Behnam, M. & Nolte, T. (2016). Semi-partitioning under a Blocking-Aware Task Allocation. In: Proceedings - Real-Time Systems Symposium: . Paper presented at 36th IEEE Real-Time Systems Symposium, RTSS 2015, 1 December 2015 through 4 December 2015.
Open this publication in new window or tab >>Semi-partitioning under a Blocking-Aware Task Allocation
2016 (English)In: Proceedings - Real-Time Systems Symposium, 2016Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Semi-partitioned scheduling is a resource efficient scheduling approach compared to the conventional multiprocessor scheduling approaches in terms of system utilization and migration overhead. Semi-partitioned scheduling can better utilize processor bandwidth compared to the partitioned scheduling while introducing less overhead compared to the global scheduling. Various techniques have been proposed to schedule tasks in a semi-partitioned environment, however, they have used blockingagnostic allocation mechanisms in presence of resource sharing protocols. Since, the allocation mechanism can highly affect the system schedulability, in this paper we provide a blocking-aware allocation mechanism for semi-partitioned scheduling framework under a suspension-based resource sharing protocol. We have applied new heuristics for sorting the tasks in the algorithm that shows improvements upon system schedulability. Finally, we present our preliminary results.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-31588 (URN)10.1109/RTSS.2015.48 (DOI)000380424600041 ()2-s2.0-84964584086 (Scopus ID)9781467395076 (ISBN)
Conference
36th IEEE Real-Time Systems Symposium, RTSS 2015, 1 December 2015 through 4 December 2015
Available from: 2016-05-13 Created: 2016-05-13 Last updated: 2016-08-18Bibliographically approved
Abbaspour, S., Gholamhosseini, H. & Lindén, M. (2015). Evaluation of wavelet based methods in removing motion artifact from ECG signal. In: IFMBE Proceedings: . Paper presented at 16th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics and Medicinteknikdagarna Joint Conferences, NBC 2014 and MTD 2014; Gothenburg; Sweden; 14 October 2014 through 16 October 2014; Code 110159 (pp. 1-4).
Open this publication in new window or tab >>Evaluation of wavelet based methods in removing motion artifact from ECG signal
2015 (English)In: IFMBE Proceedings, 2015, p. 1-4Conference paper, Published paper (Refereed)
Abstract [en]

Accurate recording and precise analysis of the electrocardiogram (ECG) signals are crucial in the pathophysiological study and clinical treatment. These recordings are often corrupted by different artifacts. The aim of this study is to propose two different methods, wavelet transform based on nonlinear thresholding and a combination method using wavelet and independent component analysis (ICA), to remove motion artifact from ECG signals. To evaluate the performance of the proposed methods, the developed techniques are applied to the real and simulated ECG data. The results of this evaluation are presented using quantitative and qualitative criteria. The results show that the proposed methods are able to reduce motion artifacts in ECG signals. Signal to noise ratio (SNR) of the wavelet technique is equal to 13.85. The wavelet-ICA method performed better with SNR of 14.23.

Keywords
ECG; ICA; Motion artifact; Wavelet transform
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:mdh:diva-26834 (URN)10.1007/978-3-319-12967-9_1 (DOI)000347893000001 ()2-s2.0-84910679330 (Scopus ID)978-3-319-12966-2 (ISBN)
Conference
16th Nordic-Baltic Conference on Biomedical Engineering and Medical Physics and Medicinteknikdagarna Joint Conferences, NBC 2014 and MTD 2014; Gothenburg; Sweden; 14 October 2014 through 16 October 2014; Code 110159
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2018-02-23Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0474-2904

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