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IEEE Wireless Communications and Networking Conference Workshops (WCNCW)

作者： Steffen Moser Luis Behrendt Frank Slomka Institute of Embedded Systems/Real-Time Systems Faculty of Engineering and Computer Science Ulm University Ulm Germany

Depending on traffic density and environmental influences, the radio channel in Vehicular Ad-Hoc Networks (VANETs) can be a limited resource. The Shannon-Hartley theorem gives a theoretical maximum amount of data which can be transmitted per time unit under given channel conditions. This limitation can be exceeded by using multi-antenna approaches commonly known as multiple-input, multiple-output (MIMO) communication systems. While these systems are already common in both infrastructural Wireless LAN (i.e. IEEE 802.11n or IEEE 802.11ac) and in modern cellular mobile networks (i.e. Long Term Evolution), the IEEE 802.11p standard for vehicleto- vehicle communication still comes without any multi-antenna approaches. In this paper we show in a simulation study that compared to plain IEEE 802.11p a MIMO-extended PHY layer based on IEEE 802.11p offers a considerably higher robustness against short-term fading caused by the vehicles' mobility and other channel-caused adverseness. Therefore we implemented a MIMO-extended PHY model using Orthogonal Space-time Block Codes (OSTBC) and linked the PHY model to a realistic MIMO radio channel model that is based on a large measurement campaign.

关键词： MIMO Receivers Diversity reception Signal to noise ratio Mathematical model OFDM

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Reconfigurable Communication Middleware for Flex Ray-Based Distributed Embedded systems

Reconfigurable Communication Middleware for Flex Ray-Based D...

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IEEE International Conference on Embedded and real-time Computing systems and Applications (RTCSA)

作者： Diptesh Majumdar Licong Zhang Purandar Bhaduri Samarjit Chakraborty Department of Computer Science and Engineering IIT Guwahati India TU Institute for Real-Time Computer Systems Munich Germany

In this paper we consider the case of a network of Electronic Control Units (ECUs) connected through a Flex Ray bus in the automotive domain. Multiple distributed applications can run on this underlying architecture, each partitioned into tasks that are mapped on different ECUs. These applications can often be executed in different functional modes with different requirements on the communication resources in terms of data size and sampling period. Moreover, new applications can be deployed on to the ECUs at run-time. To efficiently utilize the communication resources and accommodate new applications, a certain flexibility in reallocation of the resource is necessary. However, the Flex Ray bus requires static configuration of schedules and data mapping in order to guarantee a more deterministic system behavior, allowing little room for flexibility. In order to address this problem, we propose a reconfigurable communication middleware that lies between the application layer and the communication controller layer, which maps messages onto Flex Ray schedules, and can be reconfigured at runtime. The configuration is synthesized and deployed online, allowing a certain reallocation of communication resources to applications. In this paper, we describe the design of such a reconfigurable communication middleware and demonstrate its function with an implementation using industry-strength Flex Ray design tools.

关键词： Schedules Middleware Indexes Protocols Vehicles Payloads Automotive engineering

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Exploiting Job Response-time Information in the Co-Design of real-time Control systems

Exploiting Job Response-Time Information in the Co-Design of...

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IEEE International Conference on Embedded and real-time Computing systems and Applications (RTCSA)

作者： Yang Xu Karl-Erik Årzén Anton Cervin Enrico Bini Bogdan Tanasa Department of Automatic Control Lund University Sweden Scuola Superiore Sant'Anna Real-Time Systems Laboratory Italy Department of Computer and Information Science Linköping University Sweden

We consider a real-time system of multiple tasks, each task having a plant to control. The overall quadratic control cost is to be optimized. We exploit the periodicity of the task response time, which corresponds to a periodic delay pattern in the feedback control loop. Perturbed periods are used as a tool to find a finite hyper period. We present an analytical procedure to design a periodic linear-quadratic-Gaussian (LQG) controller for tasks with fixed execution times as well as a numerical solution to the periodic -- stochastic LQG problem for tasks with variable execution times. The controllers are evaluated using simulations in real-time scheduling and control co-design examples.

关键词： Delays real-time systems Control design time factors Mathematical model Numerical models Cost function

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Predictability and utilisation trade-off in the dynamic management of multiple video stream decoding on Network-on-Chip based homogeneous embedded multi-cores 14

Predictability and utilisation trade-off in the dynamic mana...

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22nd International Conference on real-time Networks and systems, RTNS 2014

作者： Mendis, Hashan Roshantha Indrusiak, Leandro Soares Audsley, Neil C. Real-time Systems Group Department of Computer Science University of York United Kingdom

ISBN: (纸本)9781450327275

Guaranteed admission control decisions in embedded multicore platforms often cause a trade-off between predictability for utilisation. The state-of-the art shows that both these objectives cannot be optimised if the workloads are dynamic and are not known a priori. Deterministic admission control approaches use worst-case response-time calculations of the tasks and flows live in the system to analytically make safe admission decisions. These tests often result in significantly under-utilised systems. Using a poor admission controller may improve system utilisation but at the cost of low-predictability. In a soft-real time system under heavy system load it is acceptable to have a few deadline misses in order to maintain relatively higher utilisation levels. This paper presents heuristic based admission control test that attempts to find a compromise between predictability and utilisation. The heuristic adjusts the estimation of subtask deadline assignment proportionally, and uses this to estimate the lateness of tasks that are admitted and live in the system. We explore the performance consequences of the proposed heuristic-based approach using an abstract simulator, and analyse its effectiveness against a deterministic admission control test under low and heavy workloads. Copyright © 2014 ACM.

关键词： Network-on-chip

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Fine-grained link locking within power and latency transaction level modelling in wormhole switching non-preemptive networks on chip 14

Fine-grained link locking within power and latency transacti...

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5th Workshop on Parallel Programming and Run-time Management Techniques for Many-Core Architectures and 3rd Workshop on Design Tools and Architectures for Multicore Embedded Computing Platforms, PARMA-DITAM 2014

作者： Harbin, James Indrusiak, Leandro Soares Department of Computer Science Real Time Systems Group University of York United Kingdom

ISBN: (纸本)9781450326070

An increasingly time-consuming part of the design flow of on-chip multiprocessors is simulation of the network on chip (NoC) architecture. Cycle-accurate simulation of state-of-the art network-on-chip interconnects can be prohibitively slow for realistic application examples. In this paper, we identify a time-predictable non-preemptive network-on-chip architecture and propose a TLM model with fine-grained locking of links. The model is tested via simulation of two benchmark application scenarios. Results demonstrate that the proposed algorithm can model the latency upon the majority of flows very closely to the cycle-accurate model, while providing more than 97% accurate power consumption modelling even on the worst case links. This is achieved while simulating nearly three orders of magnitude faster compared to a cycle-accurate model of the same interconnect. Copyright © 2014 ACM.

关键词： Network-on-chip

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Schedulability analysis for the Abort-and-Restart (AR) model 14

Schedulability analysis for the Abort-and-Restart (AR) model

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22nd International Conference on real-time Networks and systems, RTNS 2014

作者： Wong, H.C. Burns, A. Real-Time Systems Research Group Department of Computer Science University of York United Kingdom

ISBN: (纸本)9781450327275

This paper addresses the scheduling of systems that implement the abort and restart (AR) model. The AR model requires that preempted tasks are aborted. As a result high priority tasks run quickly and shared resources need not be protected (as tasks only work on copies of these resources). However there is significant wastage as low priority tasks may be subject to a series of aborts. We show that exact analysis of the AR model is intractable. Two sufficient but tractable tests are developed and are used to address the priority assignment issue. Again an optimal tractable algorithm is not available. The paper develops a priority assignment heuristic than is demonstrated to perform better than existing schemes. Copyright © 2014 ACM.

关键词： real time systems

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Efficient deep learning algorithm with accelerating inference strategy

Lecture Notes in Computer Science (including subseries Lectu...

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Lecture Notes in computer science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2014年 8933卷 394-405页

作者： Wang, Junjie Zhang, Xiaolong School of Computer Science and Technology Wuhan University of Science and Technology Wuhan430065 China Intelligent Information Processing and Real-time Industrial Systems Hubei Province Key Laboratory Wuhan430065 China

In this paper, we present an efficient learning algorithm for Deep Boltzmann Machine (DBM) to get the data-dependent expectation quickly. The algorithm adopts a layer-wise accelerating inference strategy to compute the mean values of all hidden layers, instead of the mean values by repeatedly running the equations of mean-field fixed-point until convergence. By taking advantage of layer-wise inference strategy, we can rapidly get the approximate mean values in a few iterations. This strategy also could learn efficiently a high performance model for high-dimensional high-structured sensory inputs. The proposed algorithm with layer-wise accelerating inference performs well compared to original DBM with given learning tasks. © Springer International Publishing Switzerland 2014.

关键词： Learning algorithms

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Performance comparison and optimization of channel coding for acoustic communication in shallow waters 9

Performance comparison and optimization of channel coding fo...

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9th ACM International Conference on Underwater Networks and systems, WUWNet 2014

作者： Uensal, Ufuk Moser, Steffen Slomka, Frank Institute of Embedded Systems/Real-Time Systems Faculty of Engineering and Computer Science Ulm University Albert-Einstein-Allee 11 Ulm89081 Germany

ISBN: (纸本)9781450332774

The coded communications using non-coherent orthogonal modulation and capacity-approaching binary channel codes namely low-density parity check code (LDPC) and turbo code are investigated in this paper with the focus on the main three characteristic effects of an underwater channel, namely, multi-path propagation, Doppler spread and ambient noise. Additionally, a new method was implemented and tested successfully to identify and eliminate the highamplitude noise from the received dataset.

关键词： Underwater acoustic communication

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On the optimality of RM and EDF for non-preemptive real-time harmonic tasks 14

On the optimality of RM and EDF for non-preemptive real-time...

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22nd International Conference on real-time Networks and systems, RTNS 2014

作者： Nasri, Mitra Baruah, Sanjoy Fohler, Gerhard Kargahi, Mehdi School of Electrical and Computer Engineering University of Tehran Iran Department of Computer Science University of North Carolina Chapel HillNC United States Department of Real-time Systems Technische Universität Kaiserslautern Germany

ISBN: (纸本)9781450327275

In this paper, we study non-preemptive uniprocessor realtime scheduling using the non-preemptive RM (npRM) and EDF (npEDF) scheduling algorithms. We discuss the limitations of existing studies, identifying pessimism in current schedulability analysis and inefficiencies in existing processor speedup results. Focusing on harmonic task sets, we show that even with restrictions placed on the execution times of the tasks, npRM and npEDF are not able to schedule all feasible task sets. We obtain necessary conditions for the feasibility of the harmonic tasks with arbitrary integer period ratios. Then we derive sufficient conditions for the schedulability of npRM and npEDF upon harmonic task sets. Based on these conditions, a superior speedup factor which guarantees the schedulability in cases where there are fewer restrictions on the execution times is derived. Results from simulation experiments show an average speedup factor three times less than the only existing feasible method to obtain speedup factor. Copyright © 2014 ACM.

关键词： Scheduling algorithms

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Quality-aware video decoding on thermally-constrained MPSoC platforms

Quality-aware video decoding on thermally-constrained MPSoC ...

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International Conference on Application Specific systems (ASAP), Architectures and Processors

作者： Deepak Gangadharan Jürgen Teich Samarjit Chakraborty Department of Computer Science Friedrich-Alexander University Institute for Real-Time Computer Systems TU Munich

Current mobile devices extensively run video players that are power hungry. Further, higher power densities as a result of technology scaling results in higher on-chip temperatures. Unlike general purpose computer systems, mobile devices that run on batteries cannot afford to have expensive cooling mechanisms. Therefore, in order to satisfy thermal constraints while running power hungry applications, dynamic thermal management (DTM) techniques have been employed. For multimedia applications, the techniques primarily relied on dynamic voltage and frequency scaling (DVFS) and dynamic power management (DPM) while taking care that maximum video quality is achieved. However, no prior work has exploited frame drops to lower the inserted idle times under predetermined quality constraints. In this work, we propose a DPM framework that utilizes frame drops to dynamically insert low idle times in order to satisfy a peak temperature constraint under a given quality constraint. This also reduces the end-to-end latency. The latencies are further reduced by maintaining lightweight workload histories. For the videos used in our experiments, it was observed that a small reduction in quality of 2 dB (reduction from 32 dB to 30 dB) due to frame drops in motion videos results in a maximum latency reduction of 1.7 sec.

关键词： Streaming media Quality of service Decoding Multimedia communication Degradation Measurement Thermal degradation

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