Lucia Lo Bello

Stochastic analysis of periodic real-time systems

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.

Automotive communications-past, current and future

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

Multichannel Superframe Scheduling for IEEE 802.15.4 Industrial Wireless Sensor Networks

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.

Coexistence Issues of Multiple Co-Located IEEE 802.15.4/ZigBee Networks Running on Adjacent Radio Channels in Industrial Environments

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.

Towards new hybrid networks for industrial automation

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.

Improving the real-time behavior of ethernet networks using traffic smoothing

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.

An exact stochastic analysis of priority-driven periodic real-time systems and its approximations

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.

The case for ethernet in automotive communications

Several factors seem to favor the introduction of Ethernet technology in automotive communications. The spreading of Ethernet as an in-vehicle network for todays cars or for those in the near future is being broadly announced by spokespersons for major carmakers and automotive electronics companies. Even in the scientific community there is a growing interest in the topic, shown by the increasing number of studies on the performance of Ethernet-based technologies such as Switched Ethernet or Time-Triggered Ethernet in automotive embedded systems. This position paper provides an overview on facts and trends towards the introduction of Ethernet in automotive communications and discusses how and to what extent Ethernet technology is likely to step in and provide benefits to the different automotive functional domains. The paper will also discuss which Ethernet technologies would be the possible candidates for the automotive industry.

A novel approach for dynamic traffic lights management based on Wireless Sensor Networks and multiple fuzzy logic controllers

HighlightsFlexible, scalable traffic lights dynamic control system for isolated intersections.Multiple parallel fuzzy controllers dynamically manage both the phase and green time.Outperforms other works in terms of vehicle waiting time and balancing between phases.Very effective under heavy traffic and when phases have unbalanced arrival rates.Lightweight effective implementable on COTS devices: broad practical impact expected. This paper proposes a novel approach to dynamically manage the traffic lights cycles and phases in an isolated intersection. The target of the work is a system that, comparing with previous solutions, offers improved performance, is flexible and can be implemented on off-the-shelf components. The challenge here is to find an effective design that achieves the target while avoiding complex and computationally expensive solutions, which would not be appropriate for the problem at hand and would impair the practical applicability of the approach in real scenarios. The proposed solution is a traffic lights dynamic control system that combines an IEEE 802.15.4 Wireless Sensor Network (WSN) for real-time traffic monitoring with multiple fuzzy logic controllers, one for each phase, that work in parallel. Each fuzzy controller addresses vehicles turning movements and dynamically manages both the phase and the green time of traffic lights. The proposed system combines the advantages of the WSN, such as easy deployment and maintenance, flexibility, low cost, noninvasiveness, and scalability, with the benefits of using four parallel fuzzy controllers, i.e., better performance, fault-tolerance, and support for phase-specific management. Simulation results show that the proposed system outperforms other solutions in the literature, significantly reducing the vehicles waiting times. A proof-of-concept implementation on an off-the-shelf device proves that the proposed controller does not require powerful hardware and can be easily implemented on a low-cost device, thus paving the way for extensive usage in practice.

Design and Implementation of an Educational Testbed for Experiencing With Industrial Communication Networks

This paper presents the design and implementation of an educational testbed developed for a course on industrial communication networks at the Engineering Faculty, University of Catania. The aim is to realize a platform capable of emulating various network configurations, thus enabling students to find out by themselves through practical experiments how different design choices, parameter settings, network configurations, and algorithms impact on the overall network performance. The testbed comprises a number of basic components (hosts, routers, and access points) implemented on nodes equipped with operating systems and open source software, which together make up a modular system. Each router can be loaded with data flows and monitored over preestablished time windows so as to evaluate its performance in a wide range of operating conditions. The wireless part makes it possible to configure environments with different levels of noise and bandwidth utilization so as to emulate a broad spectrum of real operating environments. The testbed can be used via remote access through a web interface that not only allows the operating conditions to be configured but also permits real-time monitoring. Students can configure the testbed on the basis of the network they are studying and can measure its performance for evaluation purposes.