Kai-Steffen Hielscher
Dr.-Ing. Kai-Steffen Jens Hielscher
More Information
Publications
2021
Simulative Evaluation of the TSN Mechanisms Time-Aware Shaper and Frame Preemption and Their Suitability for Industrial Use Cases
20th Annual IFIP Networking Conference, IFIP Networking 2021 (Virtual, Espoo, FIN, 2021-06-21 - 2021-06-24)
In: Zheng Yan, Gareth Tyson, Dimitrios Koutsonikolas (ed.): 2021 IFIP Networking Conference, IFIP Networking 2021 2021
DOI: 10.23919/IFIPNetworking52078.2021.9472830
URL: http://dl.ifip.org/db/conf/networking/networking2021/1570720396.pdf
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A Service-Oriented Real-Time Communication Scheme for AUTOSAR Adaptive Using OPC UA and Time-Sensitive Networking
In: Sensors 21 (2021)
ISSN: 1424-8220
DOI: 10.3390/s21072337
URL: https://www.mdpi.com/1424-8220/21/7/2337
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LETT: An Execution Model for Distributed Real-Time Systems
2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall) (Norman, OK, USA, 2021-09-27 - 2021-09-30)
In: IEEE (ed.): 2021 IEEE 94th Vehicular Technology Conference (VTC2021-Fall) 2021
DOI: 10.1109/VTC2021-Fall52928.2021.9625343
URL: https://ieeexplore.ieee.org/document/9625343
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Broadband Internet access via satellite: State-of-the-art and future directions
15. ITG-Fachkonferenz Breitbandversorgung in Deutschland - 15th ITG Expert Conference on Broadband Coverage in Germany (Virtual, Online, 2021-03-02 - 2021-03-03)
In: Breitbandversorgung in Deutschland - 15. ITG-Fachkonferenz 2021
URL: https://ieeexplore.ieee.org/document/9399712
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POSTER: Revisiting Multipath QUIC Experiments and Comparing them with more recent Multipath TCP Implementations
27th IEEE International Symposium on Local and Metropolitan Area Networks, LANMAN 2021 (Virtual, 2021-07-12 - 2021-07-13)
In: IEEE Workshop on Local and Metropolitan Area Networks 2021
DOI: 10.1109/LANMAN52105.2021.9478815
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2020
One-Way Delay and Goodput Measurements with a VDSL, DOCSIS, and MPTCP Internet Access
43rd International Conference on Telecommunications and Signal Processing, TSP 2020 (Milan, 2020-07-07 - 2020-07-09)
In: Norbert Herencsar (ed.): 2020 43rd International Conference on Telecommunications and Signal Processing, TSP 2020 2020
DOI: 10.1109/TSP49548.2020.9163526
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Design of a hybrid genetic algorithm for time-sensitive networking
20th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems, MMB 2020 (Saarbrücken, 2020-03-16 - 2020-03-18)
In: Holger Hermanns, Holger Hermanns (ed.): Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2020
DOI: 10.1007/978-3-030-43024-5_7
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Repeatable Simulation for Highly Automated Driving Development and Testing
2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring) (Antwerp, 2020-05-25 - 2020-05-28)
In: IEEE (ed.): Proceedings of the 2020 IEEE 91st Vehicular Technology Conference (VTC2020-Spring) 2020
DOI: 10.1109/VTC2020-Spring48590.2020.9129208
URL: https://ieeexplore.ieee.org/abstract/document/9129208
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An ns-3 model for multipath communication with terrestrial and satellite links
20th International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems, MMB 2020 (Saarbrücken, 2020-03-16 - 2020-03-18)
In: Holger Hermanns, Holger Hermanns (ed.): Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2020
DOI: 10.1007/978-3-030-43024-5_5
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Network Calculus Results for TSN: An Introduction
In: 2020 Information Communication Technologies Conference (ICTC) 2020
DOI: 10.1109/ICTC49638.2020.9123308
URL: https://ieeexplore.ieee.org/document/9123308
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2019
Satellite internet performance measurements
2019 International Conference on Networked Systems, NetSys 2019 (Garching bei München, 2019-03-18 - 2019-03-21)
In: Georg Carle, Tobias Hossfeld, Wolfgang Kellerer, Jorg Ott (ed.): Proceedings of the 2019 International Conference on Networked Systems, NetSys 2019 2019
DOI: 10.1109/NetSys.2019.8854494
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2018
Measurement-Based Evaluation of Environmental Diffraction Modeling for 3D Vehicle-to-X Simulation
10th IEEE Vehicular Networking Conference (VNC 2018) (Taipei, 2018-12-05 - 2018-12-07)
In: Proceedings of the 10th IEEE Vehicular Networking Conference (VNC 2018) 2018
DOI: 10.1109/VNC.2018.8628418
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8628418&isnumber=8628314
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Multipath Communication over Terrestrial and Satellite Links
DOI: 10.1109/LANMAN.2018.8475101
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2017
Proceedings of the 5th GI/ITG KuVS Fachgespräch Inter-Vehicle Communication (FG-IVC 2017)
(2017)
URL: http://www7.cs.fau.de/fgivc2017/
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(Techreport)
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2015
Industrial Application of Network Calculus
Network Calculus (Dagstuhl Seminar 15112) (Dagstuhl, Germany)
In: Network Calculus (Dagstuhl Seminar 15112), Schloss Dagstuhl, Wadern, Germany: 2015
DOI: 10.4230/DagRep.5.3.63
URL: http://drops.dagstuhl.de/opus/volltexte/2015/5269
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Problems of Strict and Non-strict Service Curves in Connection with Aggregate Scheduling
(2015), p. 33
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(Techreport)
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2014
Construction Methods for MDD-based State Space Representations of Unstructured Systems
MMB 2014 (Bamberg, Germany)
In: Proceedings of the 17th International GI/ITG Conference on "Measurement, Modelling and Evaluation of Computing Systems and "Dependability and Fault-Tolerance 2014
DOI: 10.1007/978-3-319-05359-2_4
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A Framework for Establishing Performance Guarantees in Industrial Automation Networks
MMB & DFT 2014 (Bamberg)
In: Proceedings MMB & DFT 2014 2014
DOI: 10.1007/978-3-319-05359-2_13
URL: http://www7.informatik.uni-erlangen.de/~klehmet/publications/Papers/In_Proceeding_MMB2014.pdf
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2013
Different Scenarios of Concatenation at Aggregate Scheduling of Multiple Nodes
The Ninth International Conference on Networking and Services (Lisbon, Portugal)
In: ICNS 2013: The Ninth International Conference on Networking and Services 2013
URL: http://www7.informatik.uni-erlangen.de/~klehmet/publications/Papers/ICNS2013.pdf
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2012
Precompiled Configuration Spaces for the Verification of Consistency in Production Planning Processes
25th European Conference on Operational Research (Vilnius (Litauen))
In: 25th European Conference on Operational Research 2012
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Multi-Valued Decision Diagrams for the Verification of Consistency in Automotive Product Data
QSIC 2012 (Xi'an, 2012-08-27 - 2012-08-29)
In: Proceedings of 12th International Conference on Quality Software (IEEE) 2012
DOI: 10.1109/QSIC.2012.43
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6319247
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Automatische Generierung des Network Calculus-Modells aus einem Simatic STEP7-Projekt
KommA 2012 (Lemgo, Germany)
In: Kommunikation in der Automation 2012
URL: http://www7.informatik.uni-erlangen.de/~ksjh/Pub/pdf/2012_KommA_NetCalc.pdf
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Network Calculus: Application to an Industrial Automation Network
MMB & DFT 2012 (Kaiserslautern)
In: MMB & DFT 2012 Workshop Proceedings 2012
URL: http://www7.informatik.uni-erlangen.de/~klehmet/publications/Papers/WoNeCa_IndustrialApplication.pdf
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Strictness of Rate-Latency Service Curves
International Conference on Data Communication Networking (Rom, 2012-07-24 - 2012-07-27)
In: Proc. of International Conference on Data Communication Networking 2012
URL: http://www7.informatik.uni-erlangen.de/~klehmet/publications/Papers/NCstrict.pdf
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2011
MDD-based Verification of Car Manufacturing Data
CimSim 2011 (Malaysia, 2011-09-20 - 2011-09-22)
In: IEEE (ed.): Third International Conference on Computational Intelligence, Modelling & Simulation (IEEE) 2011
DOI: 10.1109/CIMSim.2011.40
URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6076354
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On the Ordering of Variables of Multi-Valued Decision Diagrams
MMBnet 2011 (Hamburg)
In: Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und Verteilten Systemen 2011
URL: http://www7.informatik.uni-erlangen.de/~berndt/publications/pdf/mmbnet.pdf
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2010
Spezifikation und Implementation des CAN-Arbitrierungsverfahrens in UPPAAL
CS-2010,5 (2010), p. 11
URL: http://www.opus.ub.uni-erlangen.de/opus/frontdoor.php?source_opus=2353
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(Techreport)
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Scheduling Complex Automotive Embedded Real-Time Systems
VES 2010 (Qingdao, China, 2010-07-15 - 2010-07-17)
In: Proc. of IEEE Intern. Conf. on Vehicular Electronics and Safety 2010
DOI: 10.1109/ICVES.2010.5550932
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Schedulability Analysis in Time-Triggered Automotive Real-Time Systems
(VTC2010-Fall) (Ottawa, Canada, 2010-09-06 - 2010-09-09)
In: Proc. of 72nd IEEE Vehicular Technology Conference 2010
DOI: 10.1109/VETECF.2010.5594406
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Introduction of time dependencies in usage model based testing of complex systems
4th International Systems Conference, SysCon 2010 (San Diego, CA)
DOI: 10.1109/SYSTEMS.2010.5482341
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Model driven testing of embedded automotive systems with timed usage models
2010 IEEE International Conference on Vehicular Electronics and Safety, ICVES 2010 (Qingdao)
DOI: 10.1109/ICVES.2010.5550938
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2009
A measurement-based simulation model of a web cluster representing system and application level dynamics
Eurocon '09 (St. Petersburg, Russia, 2009-05-18 - 2009-05-23)
In: Proc. of IEEE EUROCON 2009 2009
DOI: 10.1109/EURCON.2009.5167649
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Stochastic and deterministic performance evaluation of automotive CAN communication
In: Computer Networks 53 (2009), p. 1171-1185
ISSN: 1389-1286
DOI: 10.1016/j.comnet.2009.02.008
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2008
Measurement-Based Modeling of Distributed Systems (Dissertation, 2008)
URL: http://www.opus.ub.uni-erlangen.de/opus/volltexte/2008/914/
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Delay Bounds for CAN Communication in Automotive Applications
MMB (Dortmund, Germany, 2008-03-31 - 2008-04-02)
In: Proc. 14th GI/ITG Conference Measurement, Modelling and Evaluation of Computer and Communication Systems, Berlin: 2008
URL: http://www7.informatik.uni-erlangen.de/~ksjh/Pub/pdf/Klehmet-CAN-MMB08.pdf
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Real-Time Guarantees for CAN Traffic
VTC2008-Spring (Marina Bay, Singapore, 2008-05-11 - 2008-05-14)
In: 2008 IEEE 67th Vehicular Technology Conference, Piscataway, N.J.: 2008
DOI: 10.1109/VETECS.2008.327
URL: http://www7.informatik.uni-erlangen.de/~ksjh/Pub/pdf/VTC2008-draft.pdf
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2007
Worst Case Analysis for Multiple Priorities in Bitwise Arbitration
(GI/ITG-Workshop MMBnet) (Hamburg, Germany)
In: GI/ITG-Workshop MMBnet: Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und verteilten Systemen 2007
URL: http://www.informatik.uni-hamburg.de/bib/medoc/B-281-07.pdf
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A Low-Cost High Precision Time Measurement Infrastructure for Embedded Mobile Systems
In: Sixth International Workshop on Robot Motion and Control (RoMoCo'07), Bukowy Dworek, Poland: 2007
DOI: 10.1007/978-1-84628-974-3_41
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2006
Performance Issues in Statistical Testing
MMB 2006 (Erlangen, Germany, 2006-03-27 - 2006-03-29)
In: Proc.of 13th GI/ITG Conference on Measurement, Modeling, and Evaluation of Computer and Communication Systems, Berlin: 2006
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Modeling and simulation of performance analysis for a cluster-based Web server
In: Simulation Modelling Practice and Theory 14 (2006), p. 188-200
ISSN: 1569-190X
DOI: 10.1016/j.simpat.2005.04.004
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2005
A Measurement-Based Simulation Model of a Web Cluster
ISC'2005 (Berlin, Germany, 2005-06-09 - 2005-06-11)
In: 3rd Int. Industrial Simulation Conference, Ghent, Belgium: 2005
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Analyse und Modellierung einer produktiven verteilten Webanwendung
3. GI/ITG-Workshop MMBnet 2005 (Hamburg)
In: Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und verteilten Systemen, Hamburg: 2005
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Measurement-based modeling of end-to-end delays in WLANs with ns-2
ASIM (Erlangen, Germany)
In: Proc. 18th Symposium on Simulation Techniques (ASIM) 2005
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2004
- Truchat Sébastien, Hielscher Kai-Steffen Jens, Pflaum Alexander:
Towards Cost Efficient Mobile Services
MOMM 2004 (Bali, Indonesia)
In: 2nd Int. Conf. on Advances in Mobile Multimedia, Bali: 2004
URL: http://www.ocg.at/publikationen/books/volumes/sr184.html
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2003
A Low-Cost Infrastructure for High Precision High Volume Performance Measurements of Web Clusters
TOOLS 2003 (Urbana, IL, USA)
In: Proc. 13th Conf. on Computer Performance Evaluations, Modelling Techniques and Tools, Heidelberg: 2003
URL: http://www.springerlink.com/link.asp?id=njgh082d155hnqat
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2001
Aufbau eines clusterbasierten Webservers zur Leistungsanalyse (Diploma thesis, 2001)
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Projects
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Simulation KI-unterstützter automobiler Szenarien und Protokoll-Optimierung
(Third Party Funds Group – Sub project)
Overall project: Optimierung der Konnektivität für automobile Anwendungen in hybriden Satelliten / terrestrischen 5G Netzwerken mittels künstlicher Intelligenz
Term: 2022-02-01 - 2025-01-31
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)The cooperation between Airbus Defense and Space GmbH, Fraunhofer Institute for Integrated Circuits, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and ZF Friedrichshafen AG has the common goal of increasing the connectivity for automotive applications in hybrid satellite-terrestrial 5G networks using artificial intelligence.
The FAU works primarily on concepts for the integration of automotive applications, the creation of a simulation model for the combination of vehicular and satellite communication, the integration of AI algorithms, the performance evaluation and optimization of quality-of-service related protocols, and supporting the implementation of a real-time demonstrator. Results shall be presented at scientific conferences and contribute to the standardization of 5G and future 6G networks.
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New protocols for faster Internet via satellite
(Third Party Funds Single)
Term: 2021-10-01 - 2024-09-30
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)In the QUICSAT project, the cooperation between the Friedrich-Alexander University (FAU) Erlangen-Nürnberg and ND SatCom GmbH has the common goal of improving Internet protocols and applications for geostationary satellite connections.The potential of new technologies (AQM, ECN, BBR and especially QUIC) will be examined. The ultimate goal is that Internet via satellite should perform as good as terrestrial Internet connections.
The high latency of geostationary satellites, the current architecture of Internet protocols and the constantly increasing complexity of Internet applications (especially websites) are the reason why the performance of Internet via satellite is sometimes worse than the performance of terrestrial Internet connections, even if the data rates are comparable. Newer Quality of Service (QoS) mechanisms are currently not used in satellite communication. With QUIC there is also the risk that the performance of satellite internet will decrease due to the non-applicability of Performance Enhancing Proxies.
The project makes a contribution to protocol research, standardization and reference implementations.
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MBPLE4Mobility - Continuous model-based product line development for control systems in
vehicle technology(Third Party Funds Single)
Term: 2021-07-01 - 2024-06-30
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)As part of a large consortium, the Chair of Computer Science 7 is involved in the project with the model-based system design of the vehicle communication systems under inclusion of variant diversity. For this purpose, on the one hand, an optimization for the configuration and resource design of the network architecture for different communication protocols and mechanisms is realized. On the other hand, safety analyses are performed using fault trees and extending them for product lines.
Network calculus is used for the formal verification of the required real-time properties. Therefore, suitable approaches for the scheduling methods applied in the networking technologies (e.g. TAS, priority-based, CBS, etc.) have to be formulated.
Model and code generators will be developed for automated and accelerated generation of the network optimizations. safety and real-time analyses. The results of these analyses are fed back into the modeling of the overall system.
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Satellite Internet Performance Measurements
(Non-FAU Project)
Term: 2021-01-01 - 2021-04-30
Funding source: andere Förderorganisation
URL: https://www.cs7.tf.fau.de/forschung/quality-of-service/forschungsprojekte/sat-internet-performance/This work evaluates the performance of different applications over different Internet access technologies, with focus on Internet access via satellite.
The following Internet access technologies have been selected:
- Geostationary satellites (Konnect/Eutelsat, skyDSL/Eutelsat, Bigblu/Eutelsat, Novostream/Astra Connect)
- Satellite megaconstellations in low Earth orbit (Starlink)
- Terrestrial systems as reference (o2 DSL, Congstar LTE)
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Engineering of next-generation Train Control and Management Systems (TCMS)
(Third Party Funds Single)
Term: 2018-10-01 - 2021-09-30
Funding source: Siemens AGWith the developing technologies and methods in the field of real-time communication and the constantly increasing amount of data to be transmitted, the railway industry has jumped on the bandwagon of modernizing its processes.In the field of railway applications, various manufacturers still provide different and mostly incompatible solutions. These solutions are specified for a certain constellation of a train, but in most cases they are not able to offer the correct functionality if the constellation of the train changes. In order to separate safety and time-critical areas from non-critical areas that e.g. offer services for passengers such as wireless LAN, separate networks with their own infrastructure must also be set up. That means more weight and costs for the train and its manufacturers.
In the area of real-time communications, time-sensitive networking (TSN) has proven to be a possible solution to overcome the problems mentioned above. It provides methods and mechanisms for Ethernet technology that enrich it with aspects of determinism and reliability.
With Time-Sensitive Networks (TSN), the safety and time critical domains can be merged with non-critical areas, so that the safety and time critical domains can still be guaranteed sufficient reliability and determinism and the needs of passengers are satisfied.
The aim of this research project is to test the suitability of TSN in the railway sector. The primary goal of the project is to analyse whether the requirements of safety and time-critical applications can be met with respect to deterministic network communication and bounded latencies and at the same time to prove that the fulfilment of the requirements of critical applications does not lead to a significant impairment of non-critical applications.
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Network Calculus for Time-Sensitive Networking
(Own Funds)
Term: 2018-10-01 - 2022-10-01This research project deals with the application of quality of service guarantees in Time-Sensitive Networking, in particular using Network Calculus. Real-time systems are increasingly required in industry, e.g. the automotive, automation or entertainment industries. Classical Ethernet, however, does not guarantee real-time performance, which leads the Time-Sensitive Networking Task Group (IEEE 802.1) to develop standards for real-time data transmission over Ethernet networks. These standards are summarized under the term Time-Sensitive Networking (TSN). Within the scope of this research project, the application of Network Calculus for TSN is now being investigated. Network Calculus (NC) is a system theory for deterministic performance evaluation. It uses mathematical methods to provide performance guarantees for communication systems. NC can help evaluate TSN's real-time properties, meet required latency limits, and provide insight into the optimal configuration of networks. It also enables buffer sizing and can evaluate existing or new scheduling algorithms. -
Transparent Multichannel IPv6
(Third Party Funds Single)
Term: 2017-04-01 - 2020-12-31
Funding source: Bundesministerium für Wirtschaft und Technologie (BMWi)Satellite communication is a way to provide broadband internet access all over the world. However, with geostationary satellites the propagation delay leads to very high delays in the magnitude of several hundred milliseconds. In order to improve the interactivity and responsiveness of communication systems, utilizing a second communication link can be highly beneficial.The Transparent Multichannel IPv6 (TMC-IPv6) Project aims to combine the advantages of multiple heterogeneous communication links. An illustrative example is the combination of a rural DSL connection with low data rate/low latency and a satellite connection with high data rate but high latency, which results in a users internet access with high data rate and low latency providing a better Quality of Experience (QoE).
Satellite-based internet access from different operators is provided by our project partners in order to experience realistic satellite communication environment and test potential solutions. The outdoor unit (parabolic antenna) is mounted on the roof of the Wolfgang-Händler-Hochhaus.
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Communication in energy information networks
(Own Funds)
Term: since 2017-04-01The electrical energy network is in a state of change due to the digitization and integration of decentralized energy sources. Pervasive and interconnected sensors and actuators are creating complex virtual control systems.
Based on an efficient communication network, innovative services and applications can provide an ecological, economical, stable and high-quality energy supply. A particular challenge are the diverse requirements and traffic patterns of applications that may be distributed over large areas and time critical.
The object of this research project is the replacement of proprietary solutions by a programmable communication network with standard components. These enable economical operation and high compatibility, individual requirements are fulfilled by software. The overarching goal is to make optimal use of the infrastructure of the energy and communication networks and to minimize over-provisioning. -
Requirements oriented testing with Markov chain usage models in the automotive domain
(Third Party Funds Single)
Term: 2008-11-01 - 2011-10-31
Funding source: IndustrieAs a result of the integration of increasingly elaborate and distributed functionality in modern automobiles the amount of installed electronic and software continuously grows. The associated growth in system complexity makes it inevitable that the test methods used for verification and validation keep pace with this development. Nowadays the test routine in industry usually requires each test case to be crafted manually by a test designer. The test case execution itself and test result evaluation usually are performed in an automated manner. This procedure has many drawbacks, as the crafting of single test cases is apparently awkward and error-prone and it is impractical to calculate test management criteria such as test coverage. Within this project a method is developed that overcomes these drawbacks. Markov chain usage models (MCUM) constitute the central role within this project. MCUMs are employed to describe the possible usage of the System-under-test and to derive test cases from them. On the one hand the integration of MCUMs makes it possible to develop methods to integrate test requirements formally, as to improve traceability. On the other hand they provide the basis to incorporate algorithms or strategies that allow the generation of test cases fitting to various test requirements in the automotive domain. These comprise e.g. different coverage criteria under usage or system oriented aspects. Moreover established methods exist that allow the calculation of dependability measures based on results obtained from test cases automatically generated from MCUMs. Also the test planning can be supported by indicators that are derived during the test process. The project aims for developing a method to describe test requirements formally by building a model. This model allows the derivation of test suites considering various testing aims and constraints. The tools themselves should form a part of the ITF (Integrated Testing Framework) and the process extend the current one described by EXAM and employed within the Volkswagen AG. -
Network Calculus and Optimization
(Own Funds)
Term: since 2004-03-01Network calculus (NC) is a system theory for deterministic performanceevaluation. It uses mathematical methods to provide performanceguarantees for communication systems. It can be applied in thedesign phase of future systems as well as the analysis of existingsystems. In real-time systems, the timeliness of events plays animportant role. Therefore, the classical performance evaluation based onstochastic methods that result in (stochastic) expectation values, i.e.mean values, has to be extended by mathematical tools producingguaranteed bounds for worst case scenarios. Network calculus allows toobtain upper bounds for end-to-end delays for one nodes or aseries of nodes within a network, upper bounds for the required bufferspace and bounds for the output flow.These analytic performance bounds characterize the worst-case behaviorof traffic flows and allow dimensioning the corresponding systems.
Currently, we study the applicability of NC for multiplexed flows, inparticular when the FIFO property cannot be assumed at the merging ofindividual flows. The aggregation of data flows plays an important rolein modelling the multiplexing scheme. We apply NC for performanceevaluation both of aggregate multiplexing at one node and atconcatenation of aggregated multiple nodes in different scenarios.
We have successfully introduced network calculus methods in thefield of internal automotive communication systems in industrialapplications. Embedded in-car networks need to fulfill hardreal-time constraints. While TDMA-based access schemes in FlexRayguarantee that certain bound can be met, statistical multiplexingin CAN networks only allows to calculate bounds for the highestpriority messages. By applying network calculus, we obtained boundsfor all priority classes without the need to specify a concretescheduling of the messages. Upper bounds for the amount of datathat arrives at each network node are enough to determine hardbounds for the end-to-end delay in CAN networks.Another field of application is industrial communication.Factory automation often also requires hard real-time boundsfor the end-to-end delay of messages. The use of Ethernet withpriority tagging allows cost-efficient implementation offactory automation systems. But without stringent planningof the network, the required bounds on the end-to-end delaycannot be guaranteed. Network calculus allows to obtain therequired bounds when applied in the planning phase of thenetwork. It also allows to dimension the buffers of nodes,e.g. of industrial Ethernet switches. Nowadays, some ofthe users of industrial Ethernet need to integratenon-real-time products like web cams and remote operationterminals into existing networks. Withoutadditional analysis, the additional traffic caused by devicesthat do not require hard real-time constraints willcause a violation of the bounds for the delay and bufferspace for real-time traffic. By taking into account thisnon-real-time traffic in network calculus and by applyingtraffic shaping for the non-real-time flows allows todimension the network so that all bounds are met.Network calculus is currently integrated into an existingautomated industrial network planning tool.