Dr.-Ing. Kai-Steffen Jens Hielscher

Kai-Steffen Hielscher
  • Job title: Head of Group Quality-of-Service
  • Organization: Department of Computer Science
  • Working group: Chair of Computer Science 7 (Computer Networks and Communication Systems)
  • Phone number: +49 9131 85 27932
  • Fax number: +49 9131 85 27409
  • Email:
  • Website:
  • Address:
    Martensstr. 3
    91058 Erlangen
    Room 06.159

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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 AG
    With 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.

  • Network Calculus for Time-Sensitive Networking
    (Own Funds)
    Term: 2018-10-01 - 2022-10-01
    This 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 - 2020-03-31
    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 user’s 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.

  • Communication in energy information networks
    (Own Funds)
    Term: 2017-04-01 - 2020-04-01
    The 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: Industrie
    As 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: 2004-03-01 - 2007-03-01
    Network calculus (NC) is a system theory for deterministic performance
    evaluation. It uses mathematical methods to provide performance
    guarantees for communication systems. It can be applied in the
    design phase of future systems as well as the analysis of existing
    systems. In real-time systems, the timeliness of events plays an
    important role. Therefore, the classical performance evaluation based on
    stochastic methods that result in (stochastic) expectation values, i.e.
    mean values, has to be extended by mathematical tools producing
    guaranteed bounds for worst case scenarios. Network calculus allows to
    obtain upper bounds for end-to-end delays for one nodes or a
    series of nodes within a network, upper bounds for the required buffer
    space and bounds for the output flow.
    These analytic performance bounds characterize the worst-case behavior
    of traffic flows and allow dimensioning the corresponding systems.
    Currently, we study the applicability of NC for multiplexed flows, in
    particular when the FIFO property cannot be assumed at the merging of
    individual flows. The aggregation of data flows plays an important role
    in modelling the multiplexing scheme. We apply NC for performance
    evaluation both of aggregate multiplexing at one node and at
    concatenation of aggregated multiple nodes in different scenarios.
    We have successfully introduced network calculus methods in the
    field of internal automotive communication systems in industrial
    applications. Embedded in-car networks need to fulfill hard
    real-time constraints. While TDMA-based access schemes in FlexRay
    guarantee that certain bound can be met, statistical multiplexing
    in CAN networks only allows to calculate bounds for the highest
    priority messages. By applying network calculus, we obtained bounds
    for all priority classes without the need to specify a concrete
    scheduling of the messages. Upper bounds for the amount of data
    that arrives at each network node are enough to determine hard
    bounds for the end-to-end delay in CAN networks.
    Another field of application is industrial communication.
    Factory automation often also requires hard real-time bounds
    for the end-to-end delay of messages. The use of Ethernet with
    priority tagging allows cost-efficient implementation of
    factory automation systems. But without stringent planning
    of the network, the required bounds on the end-to-end delay
    cannot be guaranteed. Network calculus allows to obtain the
    required bounds when applied in the planning phase of the
    network. It also allows to dimension the buffers of nodes,
    e.g. of industrial Ethernet switches. Nowadays, some of
    the users of industrial Ethernet need to integrate
    non-real-time products like web cams and remote operation
    terminals into existing networks. Without
    additional analysis, the additional traffic caused by devices
    that do not require hard real-time constraints will
    cause a violation of the bounds for the delay and buffer
    space for real-time traffic. By taking into account this
    non-real-time traffic in network calculus and by applying
    traffic shaping for the non-real-time flows allows to
    dimension the network so that all bounds are met.
    Network calculus is currently integrated into an existing
    automated industrial network planning tool.