Luis Llopis

A survey on quality of service support in wireless sensor and actor networks: Requirements and challenges in the context of critical infrastructure protection

Wireless sensor and actor networks (WSANs) are likely to become a pervasive technology in the near future due to the special characteristics of these devices and to the great number of applications where it can be applied. One of these applications is the critical infrastructure protection (CIP). In fact, WSANs have actually been identified as having the potential to become an integral part of the CIP. However, in order to achieve that goal, WSANs need to provide a set of features which includes a robust QoS. Unfortunately QoS support mechanisms in WSANs are still largely undeveloped. This paper studies the state-of-the-art of QoS management in WSANs by exploring existing proposals, challenges and open issues in the field. Emphasis is put on QoS in the context of CIP by focusing on the QoS requirements and the needs of CIP applications. Existing middleware and protocols are surveyed and the challenges and open issues in the field are presented.

Integrating Schedulability Analysis and Design Techniques in SDL

The usage of formal description techniques (FDTs) has arisen as a promising way of dealing with the increasing complexity of embedded real-time systems. However, FDTs do not take into account non-functional aspects, such as the time requirements, that are especially important in the context of this kind of system. In this paper, we present how to integrate real-time analysis in the context of the specification and description language (SDL) FDT. In order to get this integration a real-time execution model for SDL is presented to allow us to express hard real-time constraints and solve SDL real-time anomalies as priority inversion and the access to shared resources. Based on this model, a schedulability analysis for systems specifed in SDL is proposed. Additionally, a set of SDL design techniques are proposed to redesign the system to meet the imposed deadlines in case the system does not meet them. To illustrate our proposals, an example of a computerized numerical control (CNC) machine is presented.

HERO: A hierarchical, efficient and reliable routing protocol for wireless sensor and actor networks

It is well known that the use of clusters makes wireless sensor and actor networks more scalable, and it also reduces energy consumption and improves their performance. Most hierarchical routing and clustering protocols are designed to be efficient when the data is sent from the sensor nodes to their cluster-head but not when it is sent the opposite way. In this paper, a simple mechanism to form clusters in an efficient way by using meta-data is proposed. And, furthermore, a novelty multi-hop and fault-tolerance routing protocol able to transport data from sensor nodes to their cluster-head and vice versa in an energy-efficient way is also presented. Moreover, this approach allows developers to establish the desired reliability level (in a quantitative way) between two nodes which are N hops far away from each other. The performance and the energy consumption of our approach is studied by means of a set of experiments which have been carried out by using the COOJA simulator.

Integrating real-time analysis in a component model for embedded systems

Component-based development is a key technology in the development of software for modern embedded systems. However, standard component models and tools are not suitable for this type of systems, since they do not explicitly address real-time, memory or cost constraints. This work presents a new predictable component model for embedded systems together with a set of tools to support it. The environment allows for the development of new components that can be assembled to build complete embedded applications, including hardware interaction. The main contribution of the environment is its support for real-time analysis at the component and application level. The analysis is achieved by combining component meta-information in the form of an abstract behaviour model and a method to measure worst-case execution times in the final platform.

A service-oriented approach to facilitate WSAN application development

Due to the complex nature of developing Wireless Sensor and Actor Network (WSAN) applications it is obvious that new frameworks, tools, middleware and higher-level abstractions are needed to make the task of the developers easier. Depending on the WSAN system we want to develop, different characteristics must be taken into account but, perhaps, some of the most important are the capacity to add real-time constraints, the QoS and, of course energy saving. Our proposal USEME is a service-oriented and component-based framework which allows the easy combination of macro-programming and node-centric programming to develop real-time and efficient applications over WSANs. USEME allows the specification of real-time constraints between services, permits the use of groups to structure the network and is platform independent. Two prototypes (Imote2.Net and SunSPOT) have been implemented and several performance tests have been carried out.

A Component Framework for Wireless Sensor and Actor Networks

Wireless sensor and actor networks (WSANs) constitute an emerging and pervasive technology that is attracting increased interest for a wide range of applications. WSANs have two major requirements: coordination mechanisms for both sensor-actor and actor-actor interactions, and real-time communication to perform correct and timely actions. Additionally, the development of WSAN applications is notoriously difficult, due to the extreme resource limitations of nodes. This paper introduces a framework to facilitate the task of the application programmer taking into account these special characteristics of WSANs. We propose a real-time component model using light-weight components. In addition, a high-level coordination model based on tuple channels is integrated into the framework including high-level constructs that abstract the details of communication and facilitate the data-centric behavior of sensor queries.

A Service-Oriented Middleware for Wireless Sensor and Actor Networks

Wireless Sensor and Actor Networks are potentially one of the most important technologies of this century. There are many fields where they can be used in order to develop varied and interesting applications: high security environments, environmental monitoring, objects and events detection, military surveillance and precision agriculture. On the other hand, the ease of programming is a major barrier to the adoption of this kind of system. Recently, different high-level programming abstractions and middleware have appeared as promising solutions. In this paper, a middleware is proposed for USEME, a Service-Oriented Framework focussed on the deployment of lightweight services in sensors and actors. The high-level model supported abstracts application programmers from implementation tasks such as discovery, communication, group formation or real-time constraints.

USEME: A Service-Oriented Framework for Wireless Sensor and Actor Networks

We are in the presence of a new and powerful technology called wireless sensor and actor networks. There are many fields where we can apply this technology to develop varied and interesting applications: high security environments, environmental monitoring,industrial monitoring, medicine, precision agriculture. This technology brings the need to develop new frameworks in order to make easier the application developers task. Recently, different high-level programming abstractions and middleware have appeared as promising solutions. In this paper, a new service-oriented framework is introduced. The general scheme of the framework and a detailed description of the programming model are presented. The approach is oriented to deploy lightweight services on sensors and actors.Services can be composed among them by means of the port concept to form complex ad-hoc systems. A building monitoring and control application is described as a motivation example and it is used along the paper in order to show the expressiveness and usability of the abstract programming language proposed.

A Real-Time Component-Oriented Middleware for Wireless Sensor and Actor Networks

Wireless sensor and actor networks (WSANs) constitute an emerging and pervasive technology that is attracting increased interest for a wide range of applications. The increasing functionality of this kind of network makes it necessary to propose tools and methodologies to facilitate software development. This paper proposes a middleware called MWSAN to provide a set of high level services for sensor and actor networks. The middleware meets the component-oriented paradigm and developers can configure it depending on the actor and sensor resources. It takes into account issues such as the network configuration, the quality of service (QoS) and the coordination among actors. MWSAN is specified in UM-RTCOM, a component model oriented to real time systems adapted to WSANs that allows us to take into account real time requirements in the applications. Additionally, we present an implementation model based on RT Java for actors. In order to apply the proposed middleware we describe an example specified in UM-RTCOM and its RT Java implementation

An Object-oriented Methodology for Embedded Real-time Systems

The usage of object-oriented methodologies in conjunction with formal description techniques has arisen as a promising way of dealing with the increasing complexity of embedded real-time systems. These methodologies are currently well supported by a set of tools that allow the specification, simulation and validation of the functional aspects of these systems. However, most of these methodologies do not take into account non-functional aspects such as hardware interaction and real-time constraints, which are especially important in the context of this kind of system. Based on our experiences in developing embedded real-time systems, we present a new methodology to design them. This methodology is based on a combination of ideas from different existing methodologies (UML, OCTOPUS, etc.) together with the integration of rate-monotonic analysis in the context of the SDL formal description technique development cycle. Additionally, in order to get this integration, a real-time execution model for SDL is presented to allow us to express hard real-time constraints. The methodology pays special attention to the transition from the object model to the task model, taking into account real-time and hardware integration issues. We also illustrate our proposal by applying it to the development of a multi-handset cordless telephone.