Pedro Yuste

An Ultra-Low Power and Flexible Acoustic Modem Design to Develop Energy-Efficient Underwater Sensor Networks

This paper is focused on the description of the physical layer of a new acoustic modem called ITACA. The modem architecture includes as a major novelty an ultra-low power asynchronous wake-up system implementation for underwater acoustic transmission that is based on a low-cost off-the-shelf RFID peripheral integrated circuit. This feature enables a reduced power dissipation of 10 μW in stand-by mode and registers very low power values during reception and transmission. The modem also incorporates clear channel assessment (CCA) to support CSMA-based medium access control (MAC) layer protocols. The design is part of a compact platform for a long-life short/medium range underwater wireless sensor network.

Non-intrusive Software-Implemented Fault Injection in Embedded Systems

Critical embedded systems, like those used in avionics or automotive, have strong dependability requirements and most of them must face with fault tolerance. One of the methods typically used to validate fault tolerance mechanisms is fault injection. The idea is to study the behavior of the system in presence of faults in order to determine whether the system behaves properly or not. Software-implemented fault injection (SWIFI) techniques enable fault injection to be performed by software. Although interesting, major drawbacks of existing SWIFI techniques are the temporal and the spatial overheads they induced in the systems under study. The reduction of these overheads is thus crucial, in order to be confident on the results and conclusions of a SWIFI experiment. This paper focuses on this problem. It proposes a new non-intrusive SWIFI technique for injecting faults in embedded (system-on-chip) applications. The technique exploits the features of a standard debugging interface for embedded systems, called Nexus, in order to inject faults without temporal overhead. Then, Nexus features are also exploited in order to observe, without spatial intrusion, the behavior of the target system in presence of the injected faults. In other words, the embedded system under study can be controlled (for injecting faults) and observed (for tracing its behavior) without customizing its original structure or altering its normal execution. Since based on Nexus, the technique has also the benefit of being applicable to any Nexus-compliant system. In order to illustrate the potentials of the approach, we use an automotive embedded control unit application as a case study. Some preliminary results obtained from the experiments performed are also discussed.

INERTE: integrated nexus-based real-time fault injection tool for embedded systems

Software implemented fault injection techniques (SWIFI) enable emulation of hardware and software faults. This emulation can be based on debugging mechanisms of general purpose processors [1] or in special debugging ports of embedded processors [2]. A well-known drawback of existing SWIFI tools rely on the temporal overhead introduced in the target system. This overhead is a problem when validating real-time systems. This paper presents a new SWIFI tool (INERTE) that solves this problem by using a standard debug interface called Nexus [3]. Using Nexus, system memory can be accessed at runtime without any intrusion in the target system. Thus, INERTE is able to inject transient faults without any temporal overhead.

RFID Based Acoustic Wake-Up System for Underwater Sensor Networks

This paper presents a new Acoustic-Triggered Wake-Up system specially useful to Underwater Wireless Sensor Networks built with low-power consumption architectures. The work includes both the wake-up system description and a comparison with previous works carried out under similar features. These comparisons demonstrate the energy benefits of this new system which requires no additional hardware within the transmission and a single but efficient AT-WUp module in the reception.

SIVEH: Numerical Computing Simulation of Wireless Energy-Harvesting Sensor Nodes

The paper presents a numerical energy harvesting model for sensor nodes, SIVEH (Simulator I–V for EH), based on I–V hardware tracking. I–V tracking is demonstrated to be more accurate than traditional energy modeling techniques when some of the components present different power dissipation at either different operating voltages or drawn currents. SIVEH numerical computing allows fast simulation of long periods of time—days, weeks, months or years—using real solar radiation curves. Moreover, SIVEH modeling has been enhanced with sleep time rate dynamic adjustment, while seeking energy-neutral operation. This paper presents the model description, a functional verification and a critical comparison with the classic energy approach.

DICOS: a real-time distributed industrial control system for embedded applications

Abstract The Fault-tolerant Systems Research Group of the Technical University of Valencia has developed the distributed industrial control system (DICOS) system. This paper describes DICOS nodes. The architecture of DICOS nodes and the error detection mechanisms used are presented. These mechanisms are based on the internal capabilities of the 16-bit microcontroller used and control flow checking and deadlines control with the aid of a second 8-bit microcontroller. Experimental results about the effectiveness of those mechanisms are shown in this paper.

Hierarchical Reliability and Safety Models of Fault Tolerant Distributed Industrial Control Systems

In order to study different configurations of distributed systems hierarchical models are needed. Hierarchical models are suitable to friendly and easily study the influence of different parameters in distributed systems. In this paper a hierarchical modelling approach of a distributed industrial control system is presented. In this sense, different fault tolerant techniques to be used are evaluated and different possible system configurations are studied. Two fault tolerant architectures for the distributed system nodes are explained and their influence in the whole system is evaluated. Also the benefits of using checkpointing techniques are presented. In order to do the hierarchical models we use stochastic activity networks and the UltraSAN tool.

A highly-automated RPAS mission manager for integrated airspace

This paper addresses the problem of defining Mission Plans for Remotely Piloted Aircraft Systems (RPAS) and designing a software architecture for executing such plans. A RPAS Mission Plan for integrated airspace usually includes flight procedures in controlled airspace as well as procedures for the operations area, which usually is in a non-controlled airspace. Procedures for controlled airspaces must adhere to standard regulations, but nothing has been yet standardised for the operation in non-controlled airspaces. Some coherent extension to traditional Flight Plans is needed to specify all flight procedures in a coherent manner. This paper advocates extending ARINC-424 route definitions with RPAS specific features. On the other hand, RPAS do need a higher level of automation than manned aircraft due to many reasons: lower situational awareness, need for higher autonomy upon C2 link failures, or higher accuracy operation. This fact has important implications on the degree of automation and the definition of the Mission Plan. Firstly, different operational modes with different levels of automation are required. Secondly, traditional Flight Plans should be also extended to specify automatic flight procedures triggered by events like C2 link failures, or collision avoidance that could lead to unsafe conditions. The paper also discusses in detail the design of a Mission Manager for supporting the previous features based on a three-tiered (3T) architecture. The porting process of this architecture to an ARINC-653 compliant execution platform based on XtratuM is also introduced.

A low-power wake-up system for underwater wireless sensor modems

Asynchronous Wake-Up physical solutions offer important advantages to develop energy efficient network polices, however these solutions need specific hardware, optimal configuration of system facilities and interconnection with a core control unit. This paper presents an acoustic-oriented system that has been specifically designed to be used within underwater modems, able to react to external acoustic stimuli with ultra-low consumption.

Dependability Evaluation of Fault Tolerant Distributed Industrial Control Systems

Modern distributed industrial control systems need improvements in their dependability. In this paper we study the dependability of a fault tolerant distributed industrial control system designed in our university. This system is based on fault tolerant nodes interconnected by two communication networks. This paper begins showing the architecture of a single node in the distributed system. Reliability and safety results for this node are presented using a theoretical model based on Stochastic Activity Networks (SAN). Based on this architecture, the theoretical model of the distributed system is then presented; in order to evaluate the reliability and safety of the whole system models based on stochastic activity networks are used, and the results obtained using UltraSAN are presented.