<p>Ethernet technology is being accepted by industrial community due to its open standardization </p><p>and low cost. To meet the requirements of industrial applications, a switched Ethernet </p><p>network with hard real time guarantees using relative deadlines is presented as a first step to </p><p>verify the functionality. The goal of the project was primarily to implement a real-time </p><p>switched Ethernet with EDF (Earliest Deadline First) scheduling algorithm. </p><p>In this project, the function simulations of real-time switched Ethernet with distributed control </p><p>software have been implemented, by using a standard switch with priority-queues and the </p><p>distributed software, as well as EDF-scheduled TDMA (Time Division Medium Access). The </p><p>network topology is the star type. There is no extra hardware added into the switch and the </p><p>nodes. All functions are implemented by software and the setting in the switch. </p><p>The project focuses on hard real-time service guarantees but soft real-time traffic and non </p><p>real-time traffic, as well as real time administration are also taken into the consideration. </p><p>Our simulations show that 100 percent of the network usage could be scheduled and the result </p><p>of deterministic real-time properties of the system are achieved as expected.</p>

<p>The aim of this Master’s thesis is to develop a solution for combining speed and performance of switched Ethernet with the real time capability and determinism of sophisticated in- vehicle networks. After thorough research in vehicle network standards, their demands and features, the</p><p>Flexible Time Division Multiple Access (FTDMA) protocol of FlexRay was chosen to be applied on a switched Ethernet architecture since it can accommodate both hard real time tasks and soft real time tasks. To provide hard real time capability, what this paper focuses on, a media access method was developed by creating static TDMA schedules for each node’s sending and receiving</p><p>port according to a certain traffic assumption. To validate the developed media access algorithm several examples with different traffic assumptions and architectures were generated and</p><p>investigated based on their sending and receiving utilization. A second method for validating and thus proving the functionality of the algorithm was by simulation. Therefore the Matlab Simulink</p><p>media library extension TRUE TIME was used to simulate a simple example with 100% sending and receiving utilization for each node.</p>

<p>Real-time networks are traditionally built on proprietary standards, resulting in a interoperability issues between different real-time netork implementations and traditional data networks mainly used in back office operations.</p><p>Continuity and supplier independence are a cause of concern with current</p><p>proprietary real-time networks.</p><p>This project evaluates the capability of providing real-time traffic over</p><p>switched Ethernet with EDF scheduling algorithm implemented at both the</p><p>switch and the node. By using OMNET simulation tool at packet level, it</p><p>is shown that the EDF implementation in switched Ethernet can guarantee</p><p>real-time traffic over the network and at the same time supporting non real-time traffic.</p>

Ethernet technology is being accepted by industrial community due to its open standardization and low cost. To meet the requirements of industrial applications, a switched Ethernet network with hard real time guarantees using relative deadlines is presented as a first step to verify the functionality. The goal of the project was primarily to implement a real-time switched Ethernet with EDF (Earliest Deadline First) scheduling algorithm. In this project, the function simulations of real-time switched Ethernet with distributed control software have been implemented, by using a standard switch with priority-queues and the distributed software, as well as EDF-scheduled TDMA (Time Division Medium Access). The network topology is the star type. There is no extra hardware added into the switch and the nodes. All functions are implemented by software and the setting in the switch. The project focuses on hard real-time service guarantees but soft real-time traffic and non real-time traffic, as well as real time administration are also taken into the consideration. Our simulations show that 100 percent of the network usage could be scheduled and the result of deterministic real-time properties of the system are achieved as expected.

The aim of this Master’s thesis is to develop a solution for combining speed and performance of switched Ethernet with the real time capability and determinism of sophisticated in- vehicle networks. After thorough research in vehicle network standards, their demands and features, the Flexible Time Division Multiple Access (FTDMA) protocol of FlexRay was chosen to be applied on a switched Ethernet architecture since it can accommodate both hard real time tasks and soft real time tasks. To provide hard real time capability, what this paper focuses on, a media access method was developed by creating static TDMA schedules for each node’s sending and receiving port according to a certain traffic assumption. To validate the developed media access algorithm several examples with different traffic assumptions and architectures were generated and investigated based on their sending and receiving utilization. A second method for validating and thus proving the functionality of the algorithm was by simulation. Therefore the Matlab Simulink media library extension TRUE TIME was used to simulate a simple example with 100% sending and receiving utilization for each node.

The importance of real-time communication at the device level in a factory automation setup is a widely researched area. This research is an effort to experimentally verify if Ethernet can be used as a real-time communication standard in a factory automation setup, by observing the effects of packet delays, packet loss, and network congestion on the performance of a networked control system (NCS). The NCS experimental setup used in this research involves real-time feedback control of multiple plants like DC motors and a magnetic-levitation system connected to one or more controllers. A multi-client-multi-server architecture on a local area network (LAN) was developed using user datagram protocol (UDP) as the communication protocol. Key observations are as follows. (1) The multi-client-single-server system showed the highest packet delays compared to single-client-single-server architecture. (2) In the singleclient- single-server system, as the Ethernet link utilization increased beyond 82 percent, the average packet delays and steady-state error of the DC motor speed-control system increased by 2231 percent and 304 percent, respectively. (3) Even under high link utilization, adding an additional server to the NCS reduced average packet delays considerably. (4) With large packet sizes, higher packet rates were automatically throttled by Ethernet’s flow control mechanism affecting the real-time communication negatively. (5) In the multiclient- multi-server architecture, average packet delays at higher packet rates, and at higher packet lengths were found to be 40 percent lesser than the those of the single-clientsingle- server system and 87.5 percent lesser than those of the multi-client-single-server system.

Real-time networks are traditionally built on proprietary standards, resulting in a interoperability issues between different real-time netork implementations and traditional data networks mainly used in back office operations. Continuity and supplier independence are a cause of concern with current proprietary real-time networks. This project evaluates the capability of providing real-time traffic over switched Ethernet with EDF scheduling algorithm implemented at both the switch and the node. By using OMNET simulation tool at packet level, it is shown that the EDF implementation in switched Ethernet can guarantee real-time traffic over the network and at the same time supporting non real-time traffic.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / Powered by single-segment switched interconnection, Ethernet can be used in time-critical data acquisition applications. Unlike synchronous time division multiple access, asynchronous packet streams result in congestions and uncertain multiplexing delays. With the delay analysis in the worst case and probabilistic guaranteeing conditions, we restrict the packet-sizes, intervals or traffic burstiness a priori to regulate delay deviations within acceptable scales. Some methods of combinatorics and stochastic theory, e.g. Cumulant Generating Function and the Large Deviation Principle, are used and verified by some simulation-based computations. The influence of time varying delay for telemetry applications is also discussed in some sense.

Advanced embedded systems can consist of many sensors, actuators and processors that are deployed on one or several boards, while having a demand of interacting with each other and sharing resources. Communication between different components usually has strict timing constraints. There is thus a strong need to provide solutions for time critical communication. This thesis focuses on both the support of real-time services over standard switched Ethernet networks and the improvement of systems' real-time characteristics, such as reducing delay and jitter in processors and on communication links. Switched Ethernet has been chosen in this work because of its major advantages in industry; it supports higher bit-rates than most other current LAN (Local Area Network) technologies, including field buses, still at a low cost. We propose using a star network topology with a single Ethernet switch. Each node is connected to a separate port of the switch via a full-duplex link, thereby eliminating collisions. A solid real-time communication protocol for switched Ethernet networks is proposed in the thesis, including a real-time layer between the Ethernet layer and the TCP/IP suite. The network has the capability of supporting both real-time and non real-time traffic and assuring adaptation to the surrounding protocol standards. Most embedded systems work in a dynamic environment, where the precise behavior of the network traffic can usually not be predicted. To support real-time services, we have chosen the Earliest Deadline scheduling algorithm (EDF) because of its optimality, high efficiency and suitability for being used in adaptive schemes. To be able to increase the amount of guaranteed real-time traffic, the notion of Asymmetric Deadline Partitioning Scheme (ADPS) is introduced. ADPS allows distribution of the end-to-end deadline of a message, sent from any source node in the network to any destination node via the switch, into two sub-deadlines, one for each hop according to the load of the physical link that it must traverse. For the EDF scheduling algorithm, the feasibility test is one of the most important techniques that provides us with information about whether or not the real-time traffic can be guaranteed by the network. With the same computational complexity as the feasibility test, a method has been developed to compute the minimum EDF-feasible deadline for a real-time task. The importance of this method in real-time applications lies in that it can be effectively used to reduce the response times of specific control activities or limit their input-output jitter. To allow more flexibility in the control of delay and jitter in real-time systems, a general approach for reducing task deadlines according to the requirements of individual tasks has been developed. The method allows the user to specify a deadline reduction factor for each task in order to better exploit the available slack according to the tasks' actual requirements. / <p>Ingår även i serien: Technical report. D / Department of Computer Science and Engineering, Chalmers University of Technology, 1653-1787 ; 28</p>

<p>Server-based architectures have recently generated more interests and are currently considered for usage for communication in networks. In parallel, switched Ethernet technology has been widely adopted and used in lots of networked systems. Current requirements of networks for supporting real-time guarantees while being flexible at the same time have made the network designers to consider addition of some features to common switches. The FTT-Enabled Ethernet switch is a switch that has been developed to support the FTT (Flexible Time Triggered) paradigm. Recently, servers have been added in these types of switches in order to efficiently manage their allocated bandwidth to different types of messages.</p><p>A hierarchical network of Ethernet switches might be designed in different ways according to the overall goals and properties of the network. In this thesis, after a study on different design solutions, an architecture has been proposed based on FTT-enabled switches, motivated by their support of real-time constraints and server-based communication features. After having created the architecture, a protocol for bandwidth reservation for this hierarchically composed Ethernet switch architecture is developed. Behavior of the designed protocol is described in detail and it has been modeled using Uppaal. Moreover, the temporal behavior (timing) of the network is presented.</p>