Hoai Hoang

Switched real-time Ethernet in industrial applications - deadline partitioning

This paper presents work on a switched Ethernet network extended to allow for periodic real-time traffic, using earliest deadline first (EDF) scheduling. A scheme of asymmetrically dividing deadlines of real-time channels between the in and outgoing links to/from the switch is proposed (ADPS). The scheme is compared with the simpler approach of dividing the deadlines in two (SDPS). The results of several software simulations of setting up RT channels over a full-duplex switched Ethernet network are presented. The simulations show that the ADPS performs better than the SDPS when master-slave communication is assumed over the network.

Computing the Minimum EDF Feasible Deadline in Periodic Systems

In most real-time applications, deadlines are artifices that need to be enforced to meet different performance requirements. For example, in periodic task sets, jitter requirements can be met by assigning suitable relative deadlines and guaranteeing the feasibility of the schedule. This paper presents a method (called minD) for calculating the minimum EDF-feasible deadline of a real-time task. More precisely, given a set of periodic tasks with hard real-time requirements, which is feasible under EDF, the proposed algorithm allows computing the shortest deadline that can be assigned to an arbitrary task in the set, or to a new incoming task (periodic or aperiodic), still preserving the EDF feasibility of the new task set. The algorithm has a pseudo polynomial complexity and handles arbitrary relative deadlines, which can be less than, equal to, or greater than periods

Real-time communication for industrial embedded systems using switched Ethernet

Summary form only given. We give an overview of research on real-time communication over systems area networks (SANs). Our project is focused on developing real-time services for switched Ethernet networks, keeping the Ethernet and TCP/IP Internet communication standards. Switched Ethernet is extended to allow for periodic real-time traffic using earliest deadline first (EDF) scheduling. We have shown the advantage of supporting special communication patterns apparent in industrial and embedded systems. We have made some implementation that demonstrate the support of both guaranteed real-time communication and efficient services for parallel and distributed computer systems by an Ethernet switch with added software.

Switched real-time ethernet with earliest deadline first scheduling protocols and traffic handling

This paper provided a method to support traffic with industrial real-time applications over non-real-time LAN technology, without loss of generality to use common protocol suits like TCP/IP. In addition, real-time Ethernet communication can be extended with some support for real-time communication over a shared-medium topology, which does not require any modification to existing Ethernet hardware.There is a strong interest of using the cheap and simple Ethernet technology for industrial and embedded systems. This far, however, the lack of real-time services has prevented this change of used network technology. This paper presents enhancements to full-duplex switched Ethernet for the ability of giving throughput and delay guarantees. The switch and the end-nodes controls the real-time traffic with Earliest Deadline First (EDF) scheduling on the frame level. No modification to the Ethernet standard is needed in the network that supports both real-time and non-real-time TCP/IP communication. The switch is responsible for admission control where feasibility analysis is made for each link between source and destination. The switch broadcasts Ethernet frames regularly to clock synchronize the end nodes and to implement flow control for non-real-time traffic.

Efficient many-to-many real-time communication using an intelligent Ethernet switch

This paper presents a solution for efficient many-to-many communication over switched Ethernet. The performance of using an ordinary switch and an intelligent switch is compared, and the results of the analysis based on 100 Mbit/s fast Ethernet show that an intelligent switch used to handle many-to-many communication can give better performance (shorter latency and higher utilization) than an ordinary switch. We also extend the network to serve many-to-many traffic with real-time demands by adding a thin software layer to the intelligent Ethernet switch and the end-nodes. Earliest deadline first (EDF) scheduling is used.

A fibre-optic AWG-based real-time network and its applicability to high-performance embedded computing

In this paper, an architecture and a medium access control (MAC) protocol for a multi-wavelength optical communication network, applicable in short range communication systems like system area networks (SANs), are proposed. The main focus lies on guaranteed support for hard and soft real-time traffic. The network is based upon a single-hop star topology with an arrayed waveguide grating (AWG) at its center. Traffic scheduling is centralized in one node (residing together with the AWG in a hub), which communicates through a physical control channel. The AWGs property of spatial wavelength reuse and the combination of fixed-tuned and tunable transceivers in the nodes enable simultaneous control and data transmission. A case study with defined real-time communication requirements in the field of radar signal processing (RSP) was carried out and indicates that the proposed system is very suitable for this kind of application.