Ethernet 10BASE-T1S is an Ethernet variant, mainly intended for automotive applications, that operates at 10 Mbps on a single-pair physical layer. For the half-duplex multidrop topology, the Ethernet 10BASE-T1S standard specifies the Physical Layer Collision Avoidance (PLCA) channel access method, which enables low-latency collision-free cyclic transmissions, but does not implement any mechanism within a node to differentiate between the diverse traffic flows generated. However, in automotive applications Quality of Service (QoS) support is beneficial to meet the requirements of the diverse types of flows. For this reason, this work proposes an application-level traffic shaping mechanism to provide QoS differentiation over Ethernet 10BASE-T1S networks, and discusses the end-to-end delay results obtained via OMNeT++ simulations in a realistic automotive scenario.

The IEEE 802.3cg-2019 standard defines Ethernet 10BASE-T1S. With a data rate of 10 Mbps in half-duplex mode on a multidrop bus, Ethernet 10BASE-T1S is a suitable candidate for in-vehicle networks with zonal architectures to interconnect multiple sensors with the relevant zonal controller. The standard provides optional Physical Layer Collision Avoidance (PLCA) capabilities that support cyclic transmissions without collisions and provide short transmission delays. However, PLCA lacks explicit priority support, while priority is useful in automotive communications to handle different flows with diverse timing requirements. In this context, this work presents a simulative performance assessment of Ethernet 10BASE-T1S with PLCA enabled in a realistic zonal-based automotive scenario. Moreover, the paper addresses how to leverage the PLCA to offer a better Quality of Service (QoS) to the nodes that generate the most time-critical flows, discussing the delays obtained with different network configurations.

In a LoRaWAN network, a number of end-devices communicate with one or more gateways that forward the messages exchanged between the end-devices and the network server. The LoRaWAN downlink transmissions, i.e., the ones from the network server to the end-devices, have to comply with the strict regional duty cycle constraints that the relevant authorities (e.g., ETSI in Europe) impose on the gateways. However, as the gateways handle the downlink traffic of a large number of end-devices, they reach their duty cycle limits faster than the individual end-devices. This determines a traffic bottleneck, as no downlink transmissions are possible as long as the gateway exceeds the duty cycle limits. Ultimately, this situation can prevent the delivery of important downlinks, e.g., the acknowledgments, in mission-critical applications. This paper explores the rationale behind the introduction of a novel gateway selection strategy, called DL+, that dynamically schedules downlink traffic to enhance the downlink packet delivery ratio. DL+ leverages a weighted decision metrics that takes into account both signal quality parameters, such as RSSI and SNR, and the available duty cycle. Preliminary simulation results are presented that demonstrate the significant improvement of the downlink packet delivery ratio introduced by DL+ compared to existing baseline approaches, especially in dense network scenarios.

Bluetooth Low Energy (BLE) is widely used in several industrial IoT applications to save on costs and power consumption. In this context, to widen the coverage area while meeting the constraints of real-time messages, some applications require multi-hop communications with bounded delays. A few approaches in the literature support real-time traffic on BLE mesh networks, but they use offline configurations, which offer a limited flexibility when new connections are dynamically added based on the application requirements. This paper, instead, proposes a Runtime Connection Admission Control for BLE (RAC-BLE) that allows the BLE devices to accept at runtime new connection requests, provided that the relevant transmissions do not overlap with communications from other BLE devices. This way, RAC-BLE by design provides bounded delays on single-hop transmissions, thus enabling BLE-based real-time mesh networks. The paper provides a detailed description of the RAC-BLE approach, an analytical calculation of the worst case end-to-end delays and experimental performance evaluations. The results show that RAC-BLE significantly reduces the maximum end-to-end delays compared with those obtained by another approach in the literature. For instance, a delay reduction of 70% and 92% is measured in the case of one hop and five hops, respectively.

While the MQTT protocol is widely adopted in IoT applications, its usage for Industrial IoT is prevented by the lack of support for time-critical transmissions. For this reason, recent work has proposed the Prioritized MQTT (PrioMQTT) protocol, i.e., an MQTT extension that introduces message prioritization and schedules messages according to their priority, which reflects their temporal constraints. PrioMQTT succeeds in reducing the latencies of time-critical messages, but it cannot guarantee bounded delays, as the message priorities are not used by the underlying network level. For this reason, this work explores the integration of PrioMQTT with the Time-Sensitive Networking family of standards, in particular with the IEEE 802.1Q-2022, to handle multiple flows with diverse real-time requirements. The work also presents a preliminary experimental assessment on commercial-off-the-shelf devices.

MQTT is an application layer protocol that, thanks to its simplicity and low overhead, is widely used in the Internet of Things (IoT) devices typically found in home automation and consumer applications. The MQTT properties make it an interesting option also for Industrial IoT (IIoT) applications. However, MQTT is not specifically devised for IIoT applications requiring low-latency and the support for time-constrained transmissions. For this reason, this paper proposes an IIoT-enabled version of MQTT called a Prioritized MQTT (PrioMQTT) that is able to provide low latencies to time-critical messages. Unlike the standard MQTT, PrioMQTT adopts the UDP/IP stack, which is more suitable than TCP/IP for low-latency communications. Moreover, PrioMQTT introduces a mechanism to prioritize the time-critical messages over the non-time-critical ones. The combination of the UDP/IP stack and priority support in the PrioMQTT protocol is achieved while maintaining the compliance with the MQTT standard message format. As a result, PrioMQTT can be implemented on commercial-off-the-shelves (COTS) devices without hardware modifications. The paper describes the PrioMQTT protocol and investigates its performance through an assessment in a realistic industrial scenario and in comparison with the standard MQTT protocol.

Bluetooth Low Energy (BLE) is emerging as an appealing solution for several Industrial Internet of Things (IIoT) applications that require low cost and low power consumption. In particular, in this context, some applications need to collect data from sensors distributed over a wide area and require predictable behavior and real-time guarantees for processing such data with bounded delays. For this reason, some works in the literature proposed approaches that enable BLE-based real-time mesh networks. However, these approaches require offline configurations, thus limiting the flexibility and adaptability of the network. This work introduces a solution to build real-time mesh networks by enabling BLE devices to find a suitable configuration at runtime.

Industry 4.0 networks support a broad set of applications and services with diverse requirements on the communication latency and reliability. Thanks to its ability to support long-distance low-power communications with low-cost devices, LoRaWAN represents a very promising solution for Industry 4.0 applications. However, LoRaWAN does not offer different Quality of Service (QoS) classes to meet the diverse requirements of the different flows. This work discusses how to support multiple Medium Access Control (MAC) protocols on a LoRaWAN end-device and introduces flow mapping in LoRaWAN networks, addressing the relevant research challenges and exploring the basic design choices.

The Time-Sensitive Networking (TSN) set of standards allows to support on the same channel the different kinds of traffic flows that are typically found in automotive scenarios. This article proposes the introduction of online Earliest Deadline First-based scheduling in TSN to provide support for event-driven real-time traffic. The proposed approach, called Deadline-TSN, is an online approach, and therefore, unlike other approaches in the literature, it does not require complex offline schedule calculations. Moreover, Deadline-TSN is able to uniformly deal with real-time periodic and event-driven traffic flows. This article presents Deadline-TSN and provides both worst-case response time analysis and simulative assessments in realistic automotive scenarios.

Industrial applications that require low power consumption and wide coverage range may benefit from the adoption of the LoRa communication technology. Unfortunately, the Medium Access Control protocol standardized for LoRa, i.e., LoRaWAN, is not suitable for industrial contexts, as it lacks support for real-time flows. Moreover, to achieve a high number of message transmissions over LoRa while keeping low duty cycle values, a multi-hop communication protocol is required. This work discusses how to combine the support for real-time flows with multi-hop transmissions over LoRa, outlining the basic design choices. A preliminary assessment based on analytical calculations is also provided.

This work explores a network architecture that combines the Software-Defined Networking (SDN) paradigm with a partitioning system for real-time networks based on the Time-Sensitive Networking (TSN) standards. The aim of the addressed architecture is to enforce temporal isolation for the flows already foreseen at the network design time, so that their delays are not affected by the introduction of new flows in the network at run time. The work describes the design of the proposed architecture and presents a preliminary experimental assessment obtained over commercial-off-the-shelf TSN-compliant switches.

The increasing complexity of modern applications calls for more complex embedded computing resources, which integrate several processing units with specialized hardware and virtualization support on a single platform to boost the computation capabilities. These subsystems require a communication system able to support different flows with diverse real-time requirements. In this context, the Time-Sensitive Networking (TSN) family of standards plays an important role. This work proposes the design and the implementation of a framework for enabling TSN communications in heterogeneous platforms with virtualization. Preliminary experimental results are reported, which provide some insights on the limitations and advantages of the proposed framework.

The functionality advancements and novel customer features that are currently found in modern automotive systems require high-bandwidth and low-latency in-vehicle communications, which become even more compelling for autonomous vehicles. In a recent effort to meet these requirements, the IEEE Time-Sensitive Networking (TSN) task group has developed a set of standards that introduce novel features in Switched Ethernet. TSN standards offer, for example, a common notion of time through accurate and reliable clock synchronization, delay bounds for real-time traffic, time-driven transmissions, improved reliability, and much more. In order to fully utilize the potential of these novel protocols in the automotive domain, TSN should be seamlessly integrated into the state-of-the-art and state-of-practice model-based development processes for automotive embedded systems. Some of the core phases in these processes include software architecture modeling, timing predictability verification, simulation, and hardware realization and deployment. Moreover, throughout the development of automotive embedded systems, the safety and security requirements specified on these systems need to be duly taken into account. In this context, this work provides an overview of TSN in automotive applications and discusses the recent technological developments relevant to the adoption of TSN in automotive embedded systems. The work also points at the open challenges and future research directions.

The advent of commercial-off-the-shelf (COTS) heterogeneous multicore platforms is offering many opportunities in the market of embedded computing systems for many application scenarios. The integration of multiple computing elements in a single device entails impressive performance capabilities. At the same time, the increased complexity of emerging systems requires the integration of more subsystems and functionalities, among others the communication subsystem. This work deals with the desirable properties of software transmission mechanisms to enable TSN communications in heterogeneous platforms handled by a hypervisor. Moreover, preliminary simulation results provide some insights on the limits and the advantages of the investigated architectures.

Monitoring of vital parameters plays a key role in better understanding the clinical condition of hospitalized patients. In this perspective, the virtual biosensor for MEDIcal WARNing precursor (MEDIWARN) aims to help the medical team to take a prompt action in response to the evolution of patients' health condition. This paper presents the MEDIWARN network architecture and discusses the design challenges that such a system poses. Simulative assessments provide a preliminary evaluation of the system in realistic scenarios.

Industrial wireless sensor networks (IWSN) are expected to support in the near future a wide range of applications in which mobile nodes, for example, robots or humans, interoperate between them and with machinery. However, the real-time constraints imposed by the industrial processing make mobility support quite challenging. This article proposes an approach based on software-defined networking (SDN), herein named forwarding and time-slotted channel hopping scheduling over SDN (FTS-SDN), that handles transmission scheduling and node mobility in IWSN providing bounded end-to-end delays. The article presents the detailed design of the FTS-SDN and the implementation on commercial-off-the-shelf devices. In addition, the FTS-SDN performance are extensively discussed, providing simulation results and experimental measurements obtained in a real scenario.

The papers in this special section focus on emerging technologies and new trends in industrial informatics. Industrial informatics is a very dynamic and open-ended research area investigating the application of computing in different industrial domains. The international conference on Industrial Informatics (INDIN) was established by the IEEE Industrial Electronic Society in 2003 in order to bridge the significant gap between the high expectations of practice and the state-of-the-art in industry and academic research [item 1) in the Appendix]. Its intention is to provide a dynamic platform for researchers in industry and academy to present their cutting-edge results, and by doing that, form the global industrial informatics agenda.

One of the main features of future factories envisaged by Industry 4.0 is the integration of humans, machinery and sensors, which will be able to exchange information, trigger actions and collaborate while on the move. The management of Industrial Wireless Sensor Networks (IWSNs) including mobile nodes is a challenging target, as mobility support has a significant impact on the network complexity and management.Recently, Software Defined Networking (SDN) has been proposed as a paradigm for controlling IWSN, with the purpose of providing a smart management of mobile nodes in industrial scenarios. However, resource management, that is, slot and frequency assignment, needs ad hoc clustering strategies to avoid the waste of resources that would impair IWSN scalability. Network scalability is a crucial requisite for the successful development of both IWSN and the Industry 4.0 vision as a whole. For this reason, clustering policies are today a cutting-edge research topic.This paper exploits the SDN approach to manage IWSN and proposes a platform for the evaluation of clustering strategies which can be profitably applied to scalable IWSN that support mobility.

The IEEE 802.15.4 standard contains the specifications of protocols that are suitable for industrial applications. Each of them is tailored for a specific industrial domain. One of these protocols is the Deterministic and Synchronous Multichannel Extension (DSME), which targets general industrial and commercial application domains. The DSME protocol extends the classic IEEE 802.15.4 protocol, overcoming the limitation on the maximum number of Guaranteed Time Slots (GTSs) and providing for channel diversity to increase network robustness. However, the DSME protocol suffers from scalability problems due to the rigid structure of the DSME multi-superframe, which in large networks does not allow to handle GTSs in an efficient way. To overcome this limitation, this work proposes the Shared DSME, an approach to handle the GTSs within the multi-superframe in an efficient way, thus increasing the scalability of the DSME protocol.

Future industrial networks are envisioned to support a broad set of applications and services with diverse communication requirements that are difficult to meet adopting a single communication technology. Software-Defined Networking and network virtualization techniques represent two promising innovations and abstractions to improve the network management and to support scalable network control functions, flexible resource allocation, and changes in the network traffic.This paper draws a research direction towards software-defined management of heterogeneous Industry 4.0 communication networks, proposing a software-defined architecture that is able to support a multitude of diverse wired and wireless communication technologies, while meeting the requirements of diverse applications. The paper also provides an implementation roadmap, discussing how to extend the EmPOWER framework to fulfill the intended target, pointing at design challenges and solutions.

Low power wide area networks (LPWANs) are suitable for many applications that require low energy consumption, support for a high number of nodes, and large coverage range. Long range (LoRa) is one of the most successful LPWAN technologies, as it enables robust long-distance low power communications and it is proven to be effective in Internet of Things (IoT) applications, such as environmental monitoring and smart metering. LoRa is also promising for Industrial IoT scenarios, but its adoption is impaired by the relevant standardized medium access control protocol, LoRaWAN, that does not offer support to real-time data flows. For this reason, this article proposes RT-LoRa, a medium access strategy for LoRa that provides support for real-time flows, thus enabling the implementation of LoRa-based LPWAN for Industrial IoT applications. This article describes RT-LoRa, presents a simulative assessment in a realistic Industrial IoT scenario and provides some guidelines for the configuration of an RT-LoRa network.

Networks are a core element of many industrial and automation systems at present. Often these networks transport time- and safety-critical messages that control physical processes. Thus, timely and guaranteed delivery is an essential property of networks for such critical systems. Over the past decade, a variety of network solutions have evolved to satisfy said properties. However, these solutions are largely incompatible with each other and many system architects are forced to deploy different solutions in parallel due to their different capabilities. IEEE 802.1 Time-Sensitive Networking (TSN) is a standardization group that enhances IEEE networking standards, most prominently Ethernet-based networks, with said properties and has the unique potential to evolve as a cross-industry mainstream networking technology. In this survey paper, we give an overview of TSN in industrial communication and automation systems and discuss specific TSN standards and projects in detail as well as their applicability to various industries.

Modern cars consist of a number of complex embedded and networked systems with steadily increasing requirements in terms of processing and communication resources. Novel automotive applications, such as automated driving, rise new needs and novel design challenges that cover a broad range of hardware/software engineering aspects. In this context, this paper provides an overview of the current technological challenges in on-board and networked automotive systems. This paper encompasses both the state-of-the-art design strategies and the upcoming hardware/software solutions for the next generation of automotive systems, with a special focus on embedded and networked technologies. In particular, this paper surveys current solutions and future trends on models and languages for automotive software development, on-board computational platforms, in-car network architectures and communication protocols, and novel design strategies for cybersecurity and functional safety.

The papers in this special section focus on embedded and networked systems for intelligent vehicles and robots. Embedded and networked systems for intelligent vehicles and robots are expected to have a significant economic, societal, and technological impact on industrial and automotive applications. Among the aspects that will benefit from these technologies the first one is safety, thanks to the reduction of accidents caused by human errors. Another positive effect is expected on sustainability, thanks to the increase in transport systems efficiency. Comfort and inclusiveness will be also improved, ensuring users’ freedom for other activities and “mobility for all.” Logistics and factory automation are among the main areas that will take advantages from intelligent vehicles and robots, that are expected to play a key role in Industry 4.0 scenarios, the so-called fourth industrial revolution, where intelligent vehicles and industrial robots will move and operate autonomously and cooperatively. Such a revolution has many key enabling technologies, such as, networked sensors, actuators, and embedded computing and control platforms, that will be distributed on-board the vehicle/robot. The contribution of artificial intelligence and deep learning computing platforms is also emerging to achieve full intelligent autonomous mobility of vehicles and robots.

Nowadays the role of mobile nodes, either human workers or robots, in industrial production is becoming increasingly important. Consequently, in Industrial Wireless Sensor Networks (IWSN), alongside with reliability and realtime constraints, mobility support is becoming a compelling requirement. However, providing mobility support in IWSN is quite challenging, as the uncertainty and dynamics of industrial environments, combined with the need for supporting real-time constraints of the data and the mobility of the nodes, complicate routing. Software-Defined Networking (SDN) is considered a promising approach for reducing the complexity of network management in many contexts, including industrial automation networks. This paper therefore presents a new SDN approach to handle node mobility and scheduling in IWSN based on the Time Slotted Channel Hopping (TSCH) protocol of the IEEE 802.15.4 standard. The paper describes the proposed approach, that is called the Forwarding and TSCH Scheduling over SDN (FTS-SDN), and provides simulative performance assessments.

Recent developments in smart assistants and smart home automation are lately attracting the interest and curiosity of consumers and researchers. Speech enabled virtual assistants (often named smart speakers) offer a wide variety of network-oriented services and, in some cases, can connect to smart environments, thus enhancing them with new and effective user interfaces. However, such devices also reveal new needs and some weaknesses. In particular, they represent faceless and blind assistants, unable to show a face, and therefore an emotion, and unable to `see' the user. As a consequence, the interaction is impaired and, in some cases, ineffective. Moreover, most of those devices heavily rely on cloud-based services, thus transmitting potentially sensitive data to remote servers. To overcome such issues, in this paper we combine some of the most advanced techniques in computer vision, deep learning, speech generation and recognition, and artificial intelligence, into a virtual assistant architecture for smart home automation systems. The proposed assistant is effective and resource-efficient, interactive and customizable, and the realized prototype runs on a low-cost, small-sized, Raspberry PI 3 device. For testing purposes, the system was integrated with an open source home automation environment and ran for several days, while people were encouraged to interact with it, and proved to be accurate, reliable and appealing.

Among the Low-Power Wide Area technologies available today, LoRa is one of the most successful, as it enables robust long-distance low-power communications in the unlicensed sub_GHz Industrial, Scientific and Medical band. A number of solution providers and network operators show much interest in this technology for Industry 4.0 applications. In addition, LoRa represent a promising candidate for boosting future Industrial Internet of Things networks and services. However, the current standardized LoRaWAN Medium Access Control (MAC) protocol over LoRa does not fully cope with the requirements of industrial networks, in particular as far as the scheduling of real-time data flow is concerned. To overcome this limitation, this paper proposes Industrial LoRa, a novel medium access strategy for LoRa that enables the implementation of industrial wireless networks for Industrial Internet of Things and Industry 4.0 applications. The paper describes the proposed MAC scheme and the advantages it provides. A simulative assessment shows the performance of the proposed approach in a realistic scenario that is compliant with the requirements of soft real-time applications in Industry 4.0.

Robotics is a surprisingly old discipline, and robots have shaped industry and the various industrial revolutions for many decades. This paper covers topics relevant to the IES Technical Committee on Factory Automation, focusing in particular on the evolution of industrial robotics. After providing a historical perspective on the topic, the paper addresses current and future trends, revealing the close link between the progress in industrial robotics and the parallel evolution of industrial communication systems, which represent an enabling technology for modern industrial robotics.

There are increasing preferences to employ wireless communication technologies for high mobility, high scalability and low-cost applications in smart city development. This paper gives a brief synopsis of typical wireless technologies in smart city applications and the comparison analysis between them. The trend for smart city wireless technology is also presented. Examples, for several key applications within smart city development (healthcare, smart grid, localization) are studied and current advanced solutions supporting these applications are summarized with futuristic trends and demands are presented.

Recently, wireless sensor networks (WSNs) are emerging in various application fields thanks to their low cost and ease of deployment. In particular, the rapid increase of critical monitoring applications encourages the study and evaluation of wireless communication protocols that can fulfill the requirements of such applications. Among the WSN standards, the IEEE 802.15.4 is very promising, as it provides critical messages with the support for prioritized channel access through the Priority Channel Access mechanism. The paper assesses the behavior of an IEEE 802.15.4 wireless sensor network implementing the Priority Channel Access mechanism in a realistic monitoring scenario, focusing on the impact on critical message transmissions. The assessments are based on OMNeT++ simulations.

The IEEE Audio Video Bridging (AVB) technology is nowadays under consideration in several automation domains, such as, automotive, avionics, and industrial communications. AVB offers several benefits, such as open specifications, the existence of multiple providers of electronic components, and the real-time support, as AVB provides bounded latency to real-time traffic classes. In addition to the above mentioned properties, in the automotive domain, comparing with the existing in-vehicle networks, AVB offers significant advantages in terms of high bandwidth, significant reduction of cabling costs, thickness and weight, while meeting the challenging EMC/EMI requirements. Recently, an improvement of the AVB protocol, called the AVB ST, was proposed in the literature, which allows for supporting scheduled traffic, i.e., a class of time-sensitive traffic that requires time-driven transmission and low latency. In this paper, we present a schedulability analysis for the real-time traffic crossing through the AVB ST network. In addition, we formally prove that, if the bandwidth in the network is allocated according to the AVB standard, the schedulability test based on response time analysis will fail for most cases even if, in reality, these cases are schedulable. In order to provide guarantees based on analysis test a bandwidth over-reservation is required. In this paper, we propose a solution to obtain a minimized bandwidth over-reservation. To the best of our knowledge, this is the first attempt to formally spot the limitation and to propose a solution for overcoming it. The proposed analysis is applied to both the AVB standard and the AVB ST. The analysis results are compared with the results of several simulative assessments, obtained using OMNeT++, on both automotive and industrial case studies. The comparison between the results of the analysis and the simulation ones shows the effectiveness of the analysis proposed in this work.

Face recognition represents an appealing solution for biometrics-based unobtrusive and flexible person authentication. However, most solutions proposed in the literature suffer from some significant drawbacks, such as high computational complexity, the need for a centralized biometrics database (which is not desirable due to widespread international provisions discouraging collections of sensitive personal data), and limited scalability on a large number of enrolled subjects. We propose a novel person authentication solution based on a cascade of face recognition and pattern matching algorithms that not only provides high reliability and robustness against impostors but also stores in a personal radio frequency identification (RFID) tag all the needed individual biometrics information of the user, who therefore always remains in control, and has the exclusive availability, of such sensitive data. This paper describes the proposed approach, called RFaceID, and discusses its performance in terms of the ratio between false acceptance rate and false rejection rate and in terms of authentication time when applied to the VidTIMIT, Extended Yale B, and Mobile Biometry (MOBIO) widely adopted face databases.

The papers in this special section focus on wireless communication for use in automation of control and cyber-physical systems. Wireless communication is becoming increasingly important for industrial automation and many solutions have started to appear on the market. However, most of the available solutions target monitoring applications with slow refresh rates and with the downlink designed for best-effort traffic, thus neglecting actuators. Critical communication applications are defined as applications that require high reliability, i.e., that data packets are delivered with very high probability within a certain deadline, to avoid serious consequences (bodily injury, human losses, severe environmental impact, or great financial loss). It is challenging to simultaneously provide low latencies (end-to-end delay) and high reliability, especially over wireless links, which are inherently unpredictable. Suitable solutions exist that work well in specific contexts.

The papers in this special section focus on telecommunication services in automation applicaitons. The evolution of automation systems has always been the result of continuous improvements to state-of-the-art systems, occasionally punctuated with significant paradigm and architectural changes that acted as innovation drivers. This happened with the industrial revolutions, which had in their origin the appearance of disruptive technologies, such as the steam engine and machine tools (first industrial revolution); electrification, mass production, and assembly lines (second industrial revolution); use of microprocessors and software (third industrial revolution).

Low energy consumption and low cost are some of the primary issues that have to be addressed in Industrial Wireless Sensor Networks (IWSN). Such networks are being increasingly used to acquire sensory data that need to be processed in real-time. The Bluetooth Low Energy (BLE) protocol is an attractive solution for implementing low-cost IWSN with reduced energy consumption and high flexibility. However, the current BLE standard does not provide real-time support for data packets and is limited to a star topology. This paper presents a real-time protocol for industrial wireless mesh networks that is developed on top of the BLE and overcomes these limitations. The paper describes the protocol and provides analysis and experimental results.

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This paper deals with a way to probabilistically guarantee reliable packet delivery in WirelessHART based networks suitable for industrial control systems. We propose a new scheduling scheme, called Iterative Probabilistic Scheduling with Adaptive Relaying (IPS-AR), which consists of a static part (IPS) and a dynamic part (AR). IPS takes into account the channel characteristics and exploits relaying to achieve a minimum reliability threshold as requested by the supported industrial application. In the AR part, each relay node decides the packet to be sent based on online assessment of both the number of consecutive errors experienced by previous packets belonging to the same flow, as well as the number of copies of the packet currently available at the other relay nodes. This enables IPS-AR to achieve the desired reliability level while using the available re-sources in terms of time and bandwidth more efficiently.

The spread use of IEEE 802.11 networks in industrial automation raised the need to support multiple traffic classes with different requirements. This paper proposes a novel approach, called SchedWiFi, that provides flexible support to the scheduled traffic class, i.e., a high priority traffic class that is transmitted according to a fixed schedule, over IEEE 802.11 ad-hoc industrial networks. SchedWiFi operates on the IEEE 802.11n physical layer, thus providing high datarate, and supports multiple traffic classes with different priorities. SchedWiFi modifies the EDCA mechanism allowing to transmit scheduled traffic without requiring any predefined superframe structure, or timeslots, thus allowing for more flexible schedule of non-ST traffic.

Industrial Wireless Sensor Networks (IWSNs) are found in many application domains that require low latency, robustness, and determinism. The IEEE 802.15.4 standard is not able to cope with the requirements of these applications. For this reason, the IEEE 802.15.4e amendment was introduced, which provides novel MAC-layer profiles that are optimized for a broad range of application domains, including process automation. This paper focuses on two of these profiles, i.e., the Deterministic and Synchronous Multi-channel Extension (DSME) and the Time Slotted Channel Hopping (TSCH). The aim of the paper is twofold. First, assessing their behavior in realistic process automation scenarios. Second, comparing their performance in terms of end-to-end delay, reliability and scalability. The ultimate aim of the work is identifying the limits of those protocols, thus paving the way to further work addressing suitable approaches to tackle them.

Communication networks for cooperative mobile robot applications have to cope with some peculiar requirements that make them quite different from typical MANETs or WSNs. Recent cooperative robot applications envisage the support of low datarate communication technologies, as this choice is beneficial in terms of energy consumption, weight reduction and integration with WSNs. In this context, this paper discusses the design choices behind a novel protocol for cooperating mobile robot applications that operates on low datarate networks and is able to provide bounded latencies, mobility and reliability.

Real-time Ethernet (RTE) technologies are becoming increasingly popular, as they provide high bandwidth and are able to meet the requirements of industrial real-time communications. Among RTE protocols, the EtherCAT standard is suitable for motion control and closed-loop control applications, which require very short cycle times. As EtherCAT was specifically devised for periodic traffic, aperiodic real-time transmissions are far from being efficient, as they entail long cycle times. To overcome this limitation, this paper presents a general framework for priority-driven swapping (PdS)-based scheduling of aperiodic real-time messages over EtherCAT networks, which uniformly covers both dynamic and static priority and allows for very short cycle times. This paper provides a description of the PdS framework, a schedulability analysis for both static priority and dynamic priority scheduling, and simulative assessments obtained through OMNeT++ simulations.

Ethernet is going to play a major role in automotive communications, thus representing a significant paradigm shift in automotive networking. Ethernet technology will allow for multiple in-vehicle systems (such as, multimedia/infotainment, camera-based advanced driver assistance and on-board diagnostics) to simultaneously access information over a single unshielded twisted pair cable. The leading technology for automotive applications is the IEEE Audio Video Bridging (AVB), which offers several advantages, such as open specification, multiple sources of electronic components, high bandwidth, the compliance with the challenging EMC/EMI automotive requirements, and significant savings on cabling costs, thickness and weight. This paper surveys the state of the art on Ethernet-based automotive communications and especially on the IEEE AVB, with a particular focus on the way to provide support to the so-called scheduled traffic, that is a class of time-sensitive traffic (e.g., control traffic) that is transmitted according to a time schedule.

The Low Latency Deterministic Network (LLDN) protocol is defined in the IEEE 802.15.4e, which is an amendment to the IEEE 802.15.4 standard specifically devised to support the requirements of industrial applications. The LLDN provides a TDMA-based medium access mechanism in which the network cycle time grows linearly with the number of nodes. As a result, to offer low cycle times to applications requiring a high number of nodes, the LLDN specifications suggest to create multiple networks operating on different channels by embedding multiple transceivers in the coordinator. However, such an approach entails high costs and increases the design complexity. Moreover, the LLDN protocol foresees a star topology that limits the network area coverage. This paper proposes a novel approach, called a MultiChannel LLDN, based on a hierarchical network structure in which nodes communicate on different channels at the same time. The approach supports a high number of network nodes while maintaining short cycle times without the need for multiple transceivers in the coordinator and also provides backward compatibility with the standard LLDN. The paper presents the MultiChannel LLDN and comparative performance assessments.

This paper proposes the Multilevel Gaussian Mixture Model (ML_GMM), a novel algorithm for online, unsupervised modeling of complex motion trajectories which allows for fast and reliable abnormal trajectory detection in video surveillance. The presented approach does not directly deal with target tracking or attribution of an observation to either one or another trajectories belonging to different targets. Instead, it receives as an input a sequence of observations and considers them as produced by a reliable, yet possibly noisy, tracker. As an output, it then produces a labeling of the input sequence, as a "normal" or "abnormal" whole trajectory. The normal and abnormal trajectory domains are learned in an unsupervised fashion during the training phase and can be updated while the classifier is running, thanks to its reduced computational complexity. The novelty of the contribution is twofold. First, ML_GMM is capable of representing short-term, as well as long-term, transitions in a consistent way, thus allowing for accurate representation of long and complex trajectories and their reliable labeling as normal or abnormal. Second, it allows the learning process to be run in parallel with the discrimination process, in order to support adaptability of the model to evolving operating conditions. Experimental results show that ML_GMM outperforms a number of comparable approaches in the literature.

The Media Oriented Systems Transport (MOST) network, the current de-facto standard for in-vehicle multimedia and infotainment, does not provide support for the stream priority and serves bandwidth allocation requests based on their arrival order, irrespective of the stream importance. This work proposes a novel bandwidth allocation approach for multimedia streams on MOST150 networks that introduces the stream priority, which is used to reserve bandwidth for each stream according to its importance. The approach also exploits the ability for dynamically changing the bandwidth needs of multimedia streams through variable bitrate compression and is useful in MOST 150 networks supporting, together with multimedia streams, also bandwidth-greedy applications, such as Advanced Driver Assistance Systems.

The IEEE 802.1 Audio/Video Bridging (AVB) protocol successfully supports audio/video streaming over Ethernet networks and is also a promising candidate for industrial automation. However, several industrial automation applications feature requirements that cannot be fulfilled by the current AVB standard. The next generation of IEEE 802.1 standards, which will specifically target the requirements of automotive and industrial control, is under specification within IEEE 802.1 Working Group. Inspired by such an ongoing work, this paper addresses the introduction in IEEE AVB networks of scheduled traffic, i.e., high priority traffic that is transmitted according to a time schedule so as to ensure no interference from other traffic classes. The paper describes the proposed approach, discusses the design choices and presents a performance assessment based on OMNeT++ simulations.

EtherCAT is a real-time Ethernet protocol for factory automation applications that enables periodic data exchange with cycle times of a few microseconds thanks to the capability to process frames “on-the-fly”. EtherCAT does not provide efficient mechanisms for enabling the transmission of asynchronous real-time data from slave nodes. This paper proposes an EDF-based Swapping Approach that allows slaves to send real-time asynchronous traffic over EtherCAT networks in an efficient way, while maintaining the interoperability with standard devices. The paper describes the EDF-based Swapping Approach and presents a comparative performance evaluation with both the EtherCAT standard and an approach in the literature that exploits CAN-Like arbitration.

This paper proposes a three-tiered network architecture to support precision farming applications over large cultivated fields. The hybrid network combines IEEE 802.15.4 Wireless Sensor Networks, operating in a multichannel mode, with Switched Ethernet. The network design has to fulfill several objectives, such as, achieving a tradeoff between energy saving for battery-operated devices and timeliness of precision farming applications over large areas, while providing scalability, robustness and cost efficiency. The work presented in the paper is based on real-world specifications provided by end users, i.e. qualified farmers, during a comprehensive investigation and requirement analysis phase. The paper first discusses the constraints that drive the network design and then presents the three-tiered architecture. Finally, the performance of the network, obtained through OMNeT++ simulations, are discussed.

The PRIME (PoweRline Intelligent Metering Evolution) protocol is a very popular multicarrier narrowband PLC protocol that fits the needs of advanced metering infrastructure applications. This paper proposes a performance assessment of the PRIME MAC layer protocol obtained through OMNeT simulations in different scenarios. The contribution of the paper is twofold. The first contribution is an approach to overcome a well-known problem of discrete-event simulators, i.e., the fact that they do not provide functionalities to emulate the continuous effects of signal propagation. To solve this problem, in this paper the channel is modeled based on measurements, made on real testbeds, so our simulator embeds data taken from experiments performed in a real scenario. The second contribution is the assessment of the impact of the modulation scheme on the performance of the PRIME protocol.

Advanced Driver Assistance Systems involving cameras and the multimedia domain are both quite challenging for automotive network technologies, due to the bandwidth requirements and latency/jitter constraints they impose. Ethernet as in-car network is expected to breakthrough in both domains and the IEEE Audio Video Bridging (AVB) standard is a promising candidate. This paper reports preliminary performance assessments of AVB for ADAS, multimedia and infotainment, obtained through the simulation of realistic traffic patterns.

This paper proposes a Lightweight version of the Precision Time Protocol, called L-PTP, for implementation on Powerline communication systems. The aim of this novel protocol is to reduce the number of messages exchanged to achieve synchronization, without penalizing its quality. L-PTP introduces several modifications to the original PTP and can be implemented on COTS devices. The paper focuses on the protocol and on the benefits of its combination with a virtual clock computation performed by a dynamic clock synchronization algorithm.

The IEEE 802.15.4 protocol offers great potential for industrial wireless sensor networks, especially when operating in beacon-enabled mode over star or cluster-tree topologies. However, it is known that beacon collisions can undermine the reliability of cluster-tree networks, causing loss of synchronization between nodes and their coordinator. For this reason, this paper proposes a Multichannel Superframe Scheduling (MSS) algorithm, a novel technique that avoids beacon collisions by scheduling superframes over different radio channels, while maintaining the connectivity of all the clusters. The paper describes the MSS algorithm and addresses the advantages it provides over the time-division superframe scheduling. Analytical results are shown which provide a quantitative estimation of how the schedulability space is improved, while simulation results show that the proposed technique increases the number of schedulable clusters and the maximum cluster density. Finally, this paper proves the feasibility of the proposed approach describing a working implementation based on TinyOS.

This paper proposes a framework for probabilistic schedulability assessment of a real-time wireless factory automation network consisting of multiple automation cells, in the presence of mobile nodes that roam from one cell to another one to accomplish application tasks along a set of predefined paths. The paper contribution is an offline analysis which, on the basis of information about the parameters of the real-time flows, the network topology and the movement patterns of mobile nodes, allows the designer to obtain the probability that the network, at runtime and in the absence of faults, will be schedulable. A case study shows how to apply the proposed analysis to offline dimensioning of the wireless network.

Due to several advantages, such as flexibility, increased mobility, and lower costs, the deployment of wireless technologies in factory automation systems is rapidly growing. However, current wireless technologies, e. g., IEEE802.11 Wireless Local Area Networks (WLANs), are not able to satisfy the requirements of industrial applications in terms of real-time communication. In this paper medium access control mechanisms in IEEE 802.11 are investigated and a new isochronous MAC is proposed. In combination with a traffic scheduler specifically designed for it, typical constraints of soft real-time flows found on the factory floor can be satisfied. A preliminary analysis shows the effectiveness of the proposed combination.

The nine papers in this special section focus on information technology in automation.

Industrial wireless sensor networks have certain peculiarities which distinguish them from other kinds of WSNs. A notable difference is that in industrial deployments WSNs usually have to be integrated with wired industrial networks, because there are critical data flows that cannot be transmitted over the wireless medium. This paper proposes a network architecture and a communication protocol, called Circular Chain Data Forwarding (CCDF), that not only supports integration with a wired industrial infrastructure, but also takes advantage of such integration to deliver real-time performance, even to nodes that could not be directly covered by a sink. To achieve this goal, a chain-based mechanism is used, which integrates data forwarding with the channel access strategy. Theoretical results, confirmed by in-depth simulations, are provided to analyze the performance of the protocol in the case of both error-free and error-prone channels.

Hybrid wired/wireless network architectures combine the flexibility and inexpensiveness of WLANs with the real-time performance of wired real-time networks. This paper describes both a scheduling framework and a scheduling algorithm to handle real-time communication over the wireless section of a hybrid wired/wireless industrial network, which uses a scheduled protocol that extends the IEEE 802.11n standard. The proposed scheduling framework is able to schedule real-time flows traversing one or multiple Access Points, providing both intra- and inter-cell scheduling. Moreover, the scheduling framework offers support for three different kinds of real-time flows, i.e., periodic, aperiodic, and sporadic. A simulative analysis is also provided to assess the computation times as a function of the number of flows and the number of schedulable flows in different scenarios.

This paper discusses on-going work investigating the use of IEEE 802.15.4 in a network architecture for factory automation, which aims at satisfying the requirements of industrial applications. In particular, one of the targets of the proposed architecture is to meet the typical real-time and QoS requirements found in industrial networks in a flexible way.

In factory communication systems, wireless networks are likely to complement wired automation networks, rather than replacing them. There is therefore an increasing interest in the way wireless and wired systems will interact and form a hybrid network. The hybrid network architecture proposed in this paper specifically addresses WLAN infrastructures in industrial environments. The paper discusses design challenges and describes the proposed system architecture and its main components.

The IEEE 802.15.4 standard leaves the problem of beacon collisions in cluster-tree topologies unsolved. Some recent work tries to solve this problem, either drastically reducing scalability or introducing some non-determinism that make them unsuitable for industrial communications. In this paper we propose a novel multi-channel approach to the beacon collision avoidance problem. Thanks to the use of multiple radio channels in the same network, it enhances scalability of cluster-tree IEEE 802.15.4 networks while allowing contention-free scheduling. A Multichannel Super-frame Scheduling (MSS) algorithm is presented that, following the multichannel approach, can outperform single-channel algorithms under given analytical conditions.

The characteristics of the IEEE 802.15.4 physical and medium access layers make such a protocol a suitable candidate to support communication between sensors and actuators in industrial environments. As industrial networks may comprise a large number of sensors and actuators and the delay increases with the increased number of nodes, a possible solution to keep the delay small is the use of multiple radio channels to implement different small low-latency communication cells. Although in IEEE 802.15.4 the radio channels do not overlap, recent literature showed that some interference may actually occur. This paper provides a better understanding of cross-channel interference in co-located IEEE 802.15.4 industrial networks and proposes a general methodology for the assessment of IEEE 802.15.4 performance under different cross-channel interference conditions. This methodology allows a network designer to perform on-site but accurate assessments and can be easily deployed in real industrial environments to perform measurements directly in the environment-under-test. A case study based on COTS IEEE 802.15.4 devices is presented to show how to apply our methodology to a real scenario and to discuss the results obtained with one or multiple interferers and varying some MAC level parameters.

Topology management protocols play an important role in WSNs, managing the sleep transitions of the nodes to make data transmissions occur in an energy-efficient way, thus prolonging network lifetime. However, classical topology management protocols are not suitable for real-time WSNs, as they may introduce unbounded delays. In a previous work, we presented a static topology management protocol specifically designed for real-time WSNs which is able to provide bounded delay and routing fidelity. This paper extends such work, presenting a dynamic topology management protocol that surpasses the static approach introducing support for event-driven data transmissions and node joining at runtime and providing a novel adaptive technique for energy balancing among nodes to further increase network lifetime. This paper provides a detailed description of the dynamic protocol and simulation results on network lifetime and routing performance with comparative assessments.

In wireless sensor networks (WSNs) used in monitoring applications, the need to provide real-time traffic with an appropriate QoS typically clashes with the energy consumption constraints of the nodes, which have to work for long periods without the possibility of replacing their batteries. When both energy and QoS constraints are present, the role of topology control mechanisms is fundamental. This paper presents a topology control protocol to support energy-efficient real-time communication over WSNs. The aim of this work is to provide bounded delay for data traffic while reducing the energy consumption of the nodes. Detailed description of the protocol is given and both analytical and simulation results are presented that show the effects of our topology control protocol in terms of reduced energy consumption, increased network capacity and reduced packet loss rate.

Recent literature shows the limitations of the IEEE 802.11e protocol when handling real-time industrial traffic. This paper proposes an approach to overcome some of these limitations and improve the QoS support for real-time traffic, with only minor changes to the IEEE standard. The proposed approach tries to reduce the number of collisions, so that the available bandwidth is used more efficiently by the real-time data traffic, especially in high traffic conditions. This is achieved through a dynamic adaptation of the back-off parameters CWmin and CWmax for the different Access Categories. Such an adaptive control is performed by a fuzzy-logic controller, that takes into account both the throughput and frame retransmission count.

The aim of this paper is to allow for hybrid task sets in the context of stochastic real-time analysis. The paper goes beyond previous work by allowing for the presence of aperiodic tasks in the system. Instead of representing a task with a fixed activation period and a worst-case execution time (WCET), here a task is characterized by an arrival profile (AP) and an execution time profile (ETP), both given by random variables with known distributions. Any number of aperiodic tasks, with arbitrary arrival and execution time profiles, can be dealt with. To cope with the unbounded interference introduced by aperiodic tasks in the system, sporadic and aperiodic tasks are encapsulated within servers. The paper presents the calculus for obtaining the exact ETP of servers, which allows us to derive exact response time distributions of periodic tasks. Also, an example is used to show the potential and validity of the proposed approach.

Handoff is defined as the phase during which a mobile node has a temporary connection loss during the transfer from one wireless communication cell to another one. As in industrial applications wireless networks are often used to connect mobile devices such as, robot, trolleys, conveyors, to a control station, handoff introduces a temporary interruption of monitoring and control of the mobile device that can be disruptive. This paper proposes the Mobile Association Handoff Protocol (MAHP), which, if compared with the standard protocol, provides a notable reduction of the handoff latency.

This paper addresses on-going work on providing a model of a robust real-time wireless link intended to be used to connect a mobile platform to a ground station in a land monitoring system. This work is part of a project where the mobile platform is an unmanned aerial vehicle (UAV), equipped with embedded devices which acquire and process sensor data to be sent to the ground station. Firstly, a temporal model of the communications link relying on radio modems is developed. Secondly, measurements have been made in order to determine packet loss probability. These two results are currently used to provide a robust real-time model of the wireless communications link.

This paper addresses the problem of supporting soft real-time traffic over IEEE 802.11 wireless local area networks in the presence of competing non-real-time traffic. The proposed solution is a wireless traffic smoother (WTS) which uses as inputs the throughput and the number of frame retransmissions at the MAC level. Combining these two inputs, the WTS is able to adapt the smoothing action to the current wireless network condition. The paper discusses the WTS, also highlighting the way it advances the current state of the art. Then, the WTS performance obtained from experiments performed on a real testbed, also in comparison to another approach recently proposed in the literature, is discussed.

The paper addresses the design of long distance wireless mesh networks (LDWMNs) and deals with implementing and managing wireless links in the wireless mesh backbone. The paper first examines the features of LDWMNs and some issues they impose. Then, the paper describes a solution based on the use of full duplex wireless links and discusses the way these links are implemented and managed to overcome the previously identified problems.

The growing need for providing real-time system designers with less pessimistic results than the ones given by traditional worst-case analysis motivates several recent works on stochastic analysis methods. This paper deals with the calculation of stochastic response time profiles of tasks that are hierarchically scheduled using server-based techniques in a stochastic analysis framework. Depending on how tasks are scheduled within the server, differences in temporal performance are expected. In the paper, initial results on calculating the response time profiles for these server-scheduled tasks are outlined.

When developing embedded systems, there is currently a trend to move from a traditional federated approach, where computer systems are developed for their own dedicated hardware architecture, to an integrated approach, where computer systems are encapsulated as subsystems and later integrated on a shared hardware architecture. The task of integrating subsystems is complex, and in resource constrained systems efficient techniques and methods are required. In this paper the issue of subsystem integration is thoroughly discussed, and it is shown how to use Server-CAN, a network scheduler for the controller area network, in the context of subsystem integration. As the network is a resource shared by all subsystems in a distributed architecture, its role in the integration process is particularly important. Here, the usage of an efficient and flexible network scheduler is essential.

The Bluetooth (BT) standard, originally designed as a cable replacement technology for low-cost, effortless connection of electronic devices, is becoming quite an attractive option even in industrial communication, as it allows low-power, cheap and easy-to-build solutions to be obtained using the available BT modules and application profiles. The great recent interest in using Bluetooth in distributed process control systems (DPCSs) provides the motivation for this work, which has a twofold aim. Firstly, investigating scenarios and architectures enables full exploitation of BT capabilities in industrial communication. Secondly, exploring technological enhancements could improve the performance of the protocol even further

This paper presents a state-of-practice (SOP) overview of automotive communication technologies, including the latest technology developments. These networking technologies are classified in four major groups: (1) current wired, (2) multimedia, (3) upcoming wired and (4) wireless. Within these groups a few technologies stand out as strong candidates for future automotive networks. The goal of this paper is to give an overview of automotive applications relying on communications, identify the key networking technologies used in various automotive applications, present their properties and attributes, and indicate future challenges in the area of automotive communications

This paper describes a stochastic analysis framework which computes the response time distribution and the deadline miss probability of individual tasks, even for systems with a maximum utilization greater than one. The framework is uniformly applied to fixed-priority and dynamic-priority systems and can handle, tasks with arbitrary relative deadlines and execution time distributions.

In modern process control systems, Ethernet is achieving a leading position, proposing itself as a network capable of supporting all communication needs at all levels in the Computer Integrated Manufacturing hierarchy. The main obstacle to using Ethernet at the Field level is the nondeterminism of the Ethernet MAC protocol, which cannot provide real-time traffic with bounded channel access times. This paper focuses on industrial applications featuring soft real-time constraints, such as periodic control or industrial multimedia, which do not require deterministic guarantees on deadline meeting. To cope with this class of applications, Ethernet should be able to guarantee the timely delivery of real-time packets in statistical terms. The paper presents fuzzy traffic smoothing, a technique to perform adaptive traffic smoothing over Ethernet networks at the Field level thus enabling them to provide a statistical bound on packet delivery time. Previous work showed that the fuzzy smoother outperforms other adaptive smoothers proposed in the literature. This paper addresses fuzzy smoother optimization through genetic algorithms. The proposed optimization is applied to tune the inference engine membership functions. The results obtained show the effectiveness of the approach.

The master/slave time division duplex approach implemented in the Bluetooth MAC sublayer simplifies management of the physical communication channel, but suffers from some limitations which prevent efficient bandwidth exploitation and may affect the overall throughput and message delays. These limitation have up to now prevented Bluetooth being extensively and successfully used in areas which differ from the traditional target applications this protocol has been developed for. We address these limitations and propose alternative slave/slave operating modes which enable Bluetooth to support new kinds of applications, such as the ones typical of distributed process control systems.

The exact stochastic analysis of most real-time systems is becoming unaffordable in current practice. On one side, the exact calculation of the response time distribution of the tasks is not possible except for simple periodic and independent task sets. On the other side, in practice, tasks introduce complexities like release jitter, blocking in shared resources, stochastic dependencies, etc, which can not be handled by the periodic and independent task set model. This paper introduces the concept of pessimism in the stochastic analysis of real-time systems in the following sense: the exact probability of missing any deadline is always lower than that derived from the pessimistic analysis. Therefore, if real-time constraints are expressed as probabilities of missing deadlines, the pessimistic stochastic analysis provides safe results. Some applications of the pessimism concept are presented. Firstly, the practical problems that arise in the stochastic analysis of periodic and independent task sets are addressed. Secondly, we extend to the stochastic case some well known techniques of the deterministic analysis, such as the blocking in shared resources, and the task priority assignment.

In large-size plants, complex communication infrastructures, comprising numerous links and routers, are often needed in order to support the flow of information required for distributed process management. The aim of this paper is addressing congestion control mechanisms to be implemented inside routers in order to avoid, or at least limit, congestion and buffer overflow in a multi-hop network. The paper presents two congestion control mechanisms which exploit the features of the IPv6 protocol and experimental results obtained through measurements in a real scenario.

Task-level or job-level isolation is commonly used in real-time systems to prevent a job that overruns from affecting jobs belonging to other tasks (task-level isolation) or to the same task (job-level isolation). Although such an isolation provides the desired protection and simplifies analysis, it often results in degraded performance (in terms of deadline meeting) because it limits the exploitation of residual processor time resulting from jobs that underruns. We propose a new overrun handling method called randomized dropping that relaxes the isolation to make effective use of such residual processor time. We apply the proposed randomized dropping to the EDF scheduling and give an analysis technique to compute the probability of deadline meeting. Experimental results show that the proposed overrun handling method outperforms previous approaches based task-level or job-level isolation.

This paper describes a stochastic analysis method for general periodic real-time systems. The proposed method accurately computes the response time distribution of each task in the system, thus making it possible to determine the deadline miss probability of individual tasks, even for systems with maximum utilization factor greater than one. The method uniformly covers both fixed-priority scheduling (such as rate monotonic) as well as dynamic-priority scheduling (such as earliest deadline first) and can handle arbitrary relative deadlines and execution time distributions. The accuracy of the method is proven by comparing the results from the analysis with those obtained from simulations, as well as other methodologies in the literature.

In modern process control systems the different activities are organised by structuring plant as a hierarchy of functional levels. In order to take into account the different requirements of the traffic exchanged at the various levels in the hierarchy, communication architectures are also organised as levels of networks using different communication protocols according to their specific operating conditions. The heterogeneous nature of these networks, however, causes problems of incompatibility and complicates the exchange of information between different levels. For this reason, manufacturers and users are currently showing great interest in harmonising the communication infrastructure at the plant level, and Ethernet technology seems to be the most natural candidate for a number of practical and economic reasons. The paper addresses some issues about the use of Ethernet as a single network technology in a process control system, especially focusing on how to improve timeliness in the delivery of real-time data over a shared Ethernet network used at the field level. Two suitable approaches are presented and evaluated using simulation. One of them is priority-based, while the second is based on adaptive traffic smoothing.

This paper formulates a problem of embedded real-time system re-engineering and presents a systematic solution. Embedded real-time system re-engineering is defined as an understanding and alteration of a legacy system to guarantee newly imposed performance requirements. The performance requirements may include a real-time throughput and an input-to-output latency. The proposed approach is based on bottleneck analysis and nonlinear optimization. The inputs to the approach include a system design specified with a process network accompanied by task graphs and task schedules, and a new real-time throughput requirement specified as a system's period constraint. The output is a set of scaling factors that represent the ratios of performance upgrades for processing elements. The solution approach works in two steps. First, it identifies bottleneck processes by estimating process latencies and by analyzing resource sharing among processes. It then derives a set of linear constraints from the new throughput requirement for bottleneck processes. Second, it formulates an integer nonlinear optimization problem and solves it for scaling factors with an objective of minimizing the hardware upgrade cost. Resultant scaling factors are used for cost-effective upgrades of processing elements. To efficiently find feasible solutions, we propose the k-level diagonal search algorithm which runs in a polynomial time with respect to the number of processing elements. Simulation results also confirm this assertion.

The problem of finding the position of a mobile agent in a wide distributed system still represents an open research area. In fact, although today several mobile agent platforms have been developed, each of them implements an ad hoc naming and location policy, suitably studied to address the specific requirements deriving from the design choices made. What is really needed is a naming and location scheme of general validity, able to effectively meet all the typical requirements of mobile agent environments and thus easy to integrate into different platforms. A first contribution of the paper is the identification of the main requirements which an agent naming scheme of general validity should meet. Then, some properties are suggested to be taken into account, in order to make a qualitative naming scheme classification. The second contribution of the paper is the proposal of a "human readable" agent naming scheme, based on the distributed environment outlined in MASIF, the standardization OMG proposal for mobile agent systems. In addition, two location protocols suitable for the proposed naming scheme are presented, which are particularly appropriate for Internet/intranet environments.