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Proceedings of the 17th ACM International Symposium on Mobile Ad Hoc Networking and Computing

作者： Georg von Zengen Colin Wulf Yannic Schröder Lars C. Wolf TU Braunschweig Institute of Operating Systems and Computer Networks Braunschweig Germany

ISBN: (纸本)9781450341844

In modern industry, robots and other highly automated machines are one of the most important parts in production. For future development in production techniques these machines will work in more flexible setups. To enable such setups wireless communication needs to fulfill strict real time requirements. In this paper we present a tool to verify whether a communication method fulfills the requirements. Furthermore, it helps during development of this communication by providing debug information. All data is provided to Wireshark, an easy to extend, open source protocol analyzer.

关键词： real time networks protocol analysis ultra wide band cyber-physical systems

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Migration support for indirect transport protocols

Migration support for indirect transport protocols

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International Conference on Universal Personal Communications

作者： A. Fieger M. Zitterbart Institute of Operating Systems and Computer Networks Technical University of Braunschweig Germany

TCP as a reliable transport protocol performs well in traditional networks, but suffers significant performance reduction in hybrid networks. The higher bit and burst error probabilities of wireless links and disruptions caused by handoffs trigger TCP's congestion avoidance mechanisms even if the transmission path is not congested. The model of indirect transport protocols subdivides the end-to-end transport connection into several subconnections, operating over wired subpaths and over wireless subpaths. This way, the problem stated above can be avoided. Transport gateways are used to interconnect two subconnections. Due to the potential mobility of wireless attached stations, the migration of transport gateways to network nodes located nearby the current location of the mobile stations is needed. With a straight forward migration approach transport communication is interrupted up to 1.4 seconds. Modifications of the Mobile IP network layer to reduce disruption times are suggested. The key idea is to enable transport layer communication while transport protocol status information is forwarded to the new transport gateway and to delay the migration.

关键词： Transport protocols Mobile communication computer network reliability Delay operating systems computer errors IP networks Bandwidth Throughput Error analysis

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Adaptive Real-Time Scheduling for Cooperative Cyber-Physical systems

Adaptive Real-Time Scheduling for Cooperative Cyber-Physical...

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Industrial Cyber-Physical systems (ICPS)

作者： Georg von Zengen Jingjin Yu Lars C. Wolf Institute of Operating Systems and Computer Networks Technische Universität Braunschweig

ISBN: (数字)9781728163895

ISBN: (纸本)9781728163901

CPSs are widely used in all sorts of applications ranging from industrial automation to search-and-rescue. So far, in these applications they work either isolated with a high mobility or operate in a static networks setup. If mobile CPSs work cooperatively, it is in applications with relaxed real-time requirements. To enable such cooperation also in hard real-time applications we present a scheduling approach that is able to adapt real-time schedules to the changes that happen in mobile networks. We present a Mixed Integer Linear Programming-model and a heuristic to generate schedules for those networks. One of the key challenges is that running applications must not be interrupted while the schedule is adapted. Therefore, the scheduling has to consider the delay and jitter boundaries, given by the application, while generating the adapted schedule.

关键词： Task analysis Schedules Real-time systems Jitter Processor scheduling Job shop scheduling Topology

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Adaptive real-time scheduling for cooperative cyber-physical systems

arXiv

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arXiv 2020年

作者： Von Zengen, Georg Yu, Jingjing Wolf, Lars C. Institute of Operating Systems and Computer Networks Technische Universität Braunschweig

CPSs are widely used in all sorts of applications ranging from industrial automation to search-and-rescue. So far, in these applications they work either isolated with a high mobility or operate in a static networks setup. If mobile CPSs work cooperatively, it is in applications with relaxed real-time requirements. To enable such cooperation also in hard real-time applications we present a scheduling approach that is able to adapt real-time schedules to the changes that happen in mobile networks. We present a Mixed Integer Linear Programmingmodel and a heuristic to generate schedules for those networks. One of the key challenges is that running applications must not be interrupted while the schedule is adapted. Therefore, the scheduling has to consider the delay and jitter boundaries, given by the application, while generating the adapted schedule. Copyright © 2020, The Authors. All rights reserved.

关键词： Real time systems

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Transport protocols over wireless links

Transport protocols over wireless links

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IEEE Symposium on computers and Communications (ISCC)

作者： A. Fieger M. Zitterbart Institute of Operating Systems and Computer Networks Technical University of Braunschweig Germany

Future networking environments are expected to be hybrid, i.e., consisting of both wireless and fixed subnetworks. Due to the presence of the wireless link, the performance of end-to-end protocols (e.g., TCP) suffers degradation. One approach to overcome this performance penalty is to subdivide the end-to-end transport layer connection into two separate ones. This approach leads to performance improvements without loss of interoperability with existing networking structures. The focus of this paper is on error recovery mechanisms suitable for the transport protocol operating over the wireless subpath. These mechanisms have to address the increased bit error probability and temporary disruptions of wireless links. The efficiency of different error correction mechanisms within wireless scenarios is investigated and possible modifications that lead to higher performance are pointed out. Mobile communications are discussed in particular.

关键词： Transport protocols Error correction Wireless networks Wireless sensor networks computer networks Communication system control Automatic repeat request operating systems Wireless application protocol Degradation

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Pitfalls in Measuring Ultra Low Power Energy Harvesting Wireless Sensor networks

Pitfalls in Measuring Ultra Low Power Energy Harvesting Wire...

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Annual Conference on Wireless On Demand Network systems and Services (WONS)

作者： Sven Pullwitt Lars Wolf Institute of Operating Systems and Computer Networks TU Braunschweig Braunschweig Germany

Applications and evaluations in the area of ultra-low power energy harvesting Wireless Sensor networks (WSNs) verge toward utilizing state-of-the-art hardware with extremely low power consumption. For the evaluation of these networks, real-world deployments are a common approach where special performance logging hardware is often used in conjunction with the sensor nodes. This hardware needs to be kept simple and cost-effective to allow for scalability. At the same time, it needs to be ensured that the measurement hardware does not interfere with the performance of the sensor node, thereby distorting the evaluation results. Herein lies an especially prominent challenge with ultra-low power sensor nodes. We outline some pitfalls that should be considered when designing or selecting this hardware.

关键词： Wireless communication Wireless sensor networks Power measurement Power demand Scalability Hardware Time measurement

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Supporting tele-teaching: visualization aspects

Supporting tele-teaching: visualization aspects

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EUROMICRO Conference

作者： O. Brand L. Petrak D. Sturzebecher M. Zitterbart Institute of Operating Systems and Computer Networks Technical University of Braunschweig Germany

ISBN: (纸本)0769507808

A strong trend for using collaborative systems in teaching can be observed. Often first experience is gained by conducting seminars or lectures with existing tools, e.g., using the MBone. These tests generally find that the support of existing, mainly generic tools is not adequate for tele-teaching. While some projects directly address learning aspects these tend to be limited in scalability, mainly addressing smaller groups. Our approach is to develop a general framework and basic components which can be used in a variety of scenarios. Currently the two main scenarios are a discussion group consisting of few (about 10) participants with equal rights, and a lecture scenario with more participants (up to 100) and a lecturer in control. For these scenarios, not only aspects of session control are relevant, but as well methods to provide feedback to the lecturer about the current session. This is achieved through a combination of visualization methods customized for the selected scenario. The session control uses a graphical representation of a room typically used in the specified scenario in order to provide feedback and to allow ease of use. The control marks tools currently in use allowing the lecturer and students to easily identify and participate in the corresponding media representation (e.g., audio and video). A special feedback tool allows rating, and can be used to gain feedback from the students about the received video and audio quality, the speed of presentation or any other resource one wants a rating on.

关键词： Visualization Seminars Feedback Internet Education Video sharing Videoconference Java operating systems computer networks

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Hardware support for RSVP capable routing

Hardware support for RSVP capable routing

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IEEE Workshop on High Performance Switching and Routing

作者： T. Harbaum D. Meier M. Prinke Institute of Operating Systems and Computer Networks Technical University of Braunschweig Germany

Today's FPGA technology allows reconfigurable hardware to be integrated into standard PC hardware as well as into dedicated router systems. With a hardware like this it is possible to offer support for CPU intense parts of the forwarding process within a router. With upcoming services like RSVP additional demands is put on processing power within routers. This paper presents an implementation of several aspects of RSVP state handling in hardware in order to relieve the router or interface CPU of some aspects of RSVP processing. Special focus is on RSVP table maintenance. The RSVP implementation uses the happlet (hardware applet) concept of Harbaum et al. (see Proceedings of ARCS '99, Jena, Germany, October 1999) to interface between the hardware based routines and the system kernel and user-space programs.

关键词： Hardware Routing Payloads operating systems computer networks Field programmable gate arrays Kernel Internet Switches Diffserv networks

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Compressing SOAP messages by using differential encoding

Compressing SOAP messages by using differential encoding

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IEEE International Conference on Web Services (ICWS)

作者： C. Werner C. Buschmann Institute of Operating Systems and Computer Networks TU Braunschweig Braunschweig Germany

A major drawback of using SOAP for application integration is its enormous demand for network bandwidth. Compared to classical approaches like Java-RMI and CORBA, SOAP messages typically cause more than three times more network traffic. In this paper we will give a detailed survey of state of the art binary encoding strategies for SOAP and introduce a new experimental concept for SOAP compression, which makes use of the commonly available WSDL description of a SOAP Web service.

关键词： Simple object access protocol Encoding XML Bandwidth Java Telecommunication traffic computer networks Web services Streaming media Transport protocols

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How Different Transceiver Hardware Effects Concurrent Transmissions in WSNs

How Different Transceiver Hardware Effects Concurrent Transm...

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International Conference on Distributed Computing in Sensor systems (DCOSS)

作者： Georg von Zengen Alexander Baumstark Alexander Willecke Ulf Kulau Lars Wolf Institute of Operating Systems and Computer Networks Technische Universität Braunschweig

The efficiency and effectiveness of network flooding protocols has recently been shown by many publications as well as real world deployments. One notable protocol is Glossy which combines Concurrent Transmission (CT) with Constructive Interference (CI). A drawback of Glossy is that up to now it has only been implemented and evaluated for one type of radio transceiver. In this paper we first present the Glossy implementation for an AT86RF233 radio transceiver which simplifies the packet forwarding due to a shared receive and transmit buffer. We evaluate our implementation against the original Glossy implementation in a minimalist setup as well as in a real world testbed. However, we observed a noticeable difference in the timing accuracy of the transceiver chips but without adverse effects on the network's performance. For this reason, in the second part of this paper we provide a deeper investigation by using Software Defined Radios to emulate concurrent transmission for different types of transceivers. This work confirms the general benefit of constructive interference but also shows its limitations. Moreover, we give novel insight into hardware dependability of constructive interference in concurrent transmissions.

关键词： Protocols Transceivers Wireless sensor networks Interference IEEE 802.15 Standard Packet loss

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