Synchronous Distributed Jam Signalling (SDJS) is a new transmission scheme targeted to highly mobile and ad hoc wireless systems. It is based on the synchronous, parallel and superimposing emission of jam signal on the physical layer. SDJS is intended to be implemented as a feature on existing standards. It enables those system with the ability to fast estimate statistical parameters. This paper presents SDJS in general and then focuses on the application to estimate the parameter number of devices in a mobile setting. We studied SDJS and its application through a mathematical model and simulations and proved the idea in a realworld implementation on a mobile network, where we estimated the number of devices in real time (within 5ms), increasing the estimation speed compared to traditional approaches by factor 1000.

This paper focuses on QoS analysis carried out through analytical modelling and experimental evaluation. QoS is defined as a set of qualitative and quantitative characteristics of a (sub)system, which are necessary for obtaining the required functionality of an application. Its analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with the user requirements. In this paper, we concentrate on a family of group communication protocols in a wireless environment, which is used as the reference system to which the QoS analysis is applied. Specific indicators have been defined and evaluated, which capture the main characteristics of the protocols and of the environment, focusing our attention on performance and dependability attributes. The model-based analysis is devoted to give an estimate of the coverage of the protocol assumptions and performance. We integrate the analytical modelling with fine-grained experimental measurements to determine realistic parameters of message delays and messages losses, and we compare the measured protocol performance with the analytical results. The main purpose of our analysis is to provide a fast, cost effective, and formally sound way to further analyse and understand the protocol behaviour and its environment.

In this paper we describe GEA-- an interface that enables the development of event-driven network protocols, their testing in a simulated network and deployment using a single, unmodified code. Normally testing and deployment requires separated implementations which results in a significant development and maintenance overhead. This is due to the different APIs of the underlying systems. As a solution to this problem we propose a common, generic event based interface called GEA. We present its design principles and show by example how to implement a network protocols with it. Finally we compare the execution of the protocol implementation in both environments to show the effectiveness of our approach.

QoS (defined as a proper set of quantitative characteristics) analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with user requirements. In this paper, we describe an analytical approach for the evaluation of the QoS offered by a family of group communication protocols in a wireless environment, and use experimental data for feeding our models. Specific

Abstract. The domain of services for mobile communication terminals has long become a fast-moving target. Indeed, this domain has been affected by a continuous stream of technological advances on aspects ranging from physical infrastructures to mobile terminals. As a result, services for this domain are known to be very unpredictable and volatile. This situation is even worse when considering services relying heavily on multimedia activities (e.g., games, audio and/or video messages, etc.). Such an application area is very sensitive to a large variety of aspects such as terminal capabilities (graphics, CPU, etc.), bandwidth, service provider’s billing policies, QoS, and user expectations. To address these issues, we present a paradigm based on domain-specific languages (DSLs) that enables networking and telecommunication experts to quickly develop robust communication services. Importantly, we propose implementation strategies to enable this paradigm to be supported by existing software infrastructures. Our DSL paradigm is uniformly used to develop a platform for communication services, named Nova. This platform addresses various domains of services including telephony services, e-mail processing, remotedocument processing, stream processing, and HTTP resource adaption. 1

The paper describes a mobile application for traffic telematics, based on the Jini middleware. The application is realized as a set of user-level services, characterized by following properties: The services should be proactive, i.e. they act on behalf of the user based on the user's preferences. Secondly, context information derived from floating car data is used to improve the quality of the proactive service and thirdly, mechanisms are introduced to cope with the inherent unreliability of the wireless communication channel. The paper also briefly presents some basic measurements on packet transfer rates over a wireless IEEE 802.11 communication link.

One of the main reasons explaining the success of field-busses in industrial automation was the drastic reduction of wiring, thus allowing for flexible reconfigurations at low cost. A possible next step, which allows even more flexibility, would be to abandon wires at all and to rely on a wireless medium for communication. However, the question of the reliability and real-time guarantees arises. In this paper, we present and evaluate a reliable real-time communication protocol that enhances the IEEE 802.11 standard. The reliability and real-time properties of the protocol rely on determining parameters that model basic assumptions on the occurrences of message losses and bounds of message delays. We determine realistic parameters by fine-grained measurements of message delays and message losses and we measure the protocol performance resulting from the so determined parameters. 1. Introduction Among the main reasons explaining the success of field-busses in industrial automation was ...

QoS analysis is a necessary step for the early verification and validation of an appropriate design, and for taking design decisions about the most rewarding choice, in relation with user requirements. The area of distributed applications, whose development is increasing more and more, favoured by the high connectivity provided by advanced Internet and Web technologies, poses special challenges in this respect. In this chapter, we describe an analytical approach for the evaluation of the QoS offered by two group communication protocols in a wireless environment. Experimental data are used both to feed the models and to validate them. Specific performance and dependability related indicators have been defined and evaluated. To improve the utility of our study, we analysed the protocols taking into account relevant phenomena affecting the environment in which such protocols are called to operate. Specifically, the fading phenomenon and the user mobility have been explicitly introduced in our models, to evaluate their impact on the correlation among successive packet transmissions. Also, in order to enhance the correctness of the derived models, a formal description of the protocols has been performed, adopting the timed asynchronous system model. The aim of this work is to provide a fast, cost effective, and formally sound way to analyse and understand protocols behaviour and their environment.

The increasing complexity of current real-time applications demands systems to make good use of the available computational resources. Guaranteeing timing behavior using traditional real-time scheduling policies is turning to be unfeasible, as these policies are based in pessimistic worst-case assumptions that preallocate resources even though they will be rarely used. The Time-Aware Fault-Tolerant (TAFT) scheduler presents a flexible scheduling strategy that allows the construction of schedules maximizing the CPU utilization. This work presents the use of the TAFT scheduler with a computational intensive distributed embedded application, in order to keep a high ratio of successful tasks completion and so guaranteeing its computational progress. More specifically, the paper sketches a “TAFTbased” fusion algorithm for laser-scanner data and derives the requirements that the execution of this algorithm has on the CPU-scheduling. 1

At this early phase of the 21st century, distributed computing (DC) is not just an advanced mode of computing; it is the main mode. Moreover, the technological advances that DC fosters—in terms of scale and complexity—are occurring faster than at any point in DC’s 25year history. From the beginning of the DC era, fault tolerance had been touted as one of the main advantages of shifting system design from centralized structures into more distributed structures. As the 21st century has begun, it seems fitting to reflect on the evolution of fault-tolerant DC technology. This article aims to examine the major unresolved issues of the 20th century, especially those that the research community must address for fault-tolerant DC to advance to the next level. Some issues might not be sufficiently resolved by the end of this decade. One emerging trend is the prevalence of real-time applications and embedded systems. Thus, this article will also address the issues that must be resolved to advance the real-time, faulttolerant DC field. Liveliness of the fault-tolerant DC field Page 1 of 13