Hybrid Approach for Energy-Aware Synchronization in Sensor Networks

This book chapter discusses a time synchronization scheme for wireless sensor networks that aims to save sensor battery power while maintaining network connectivity for as long as possible

Hybrid Energy-Aware Synchronization Algorithm in Wireless Sensor Networks

This paper discusses a time synchronization scheme for wireless sensor networks that aims to conserve sensor battery power while maintaining network connectivity for as long as possible

Acquiring Authentic Data in Unattended Wireless Sensor Networks

An Unattended Wireless Sensor Network (UWSN) can be used in many applications to collect valuable data. Nevertheless, due to the unattended nature, the sensors could be compromised and the sensor readings would be maliciously altered so that the sink accepts the falsified sensor readings. Unfortunately, few attentions have been given to this authentication problem. Moreover, existing methods suffer from different kinds of DoS attacks such as Path-Based DoS (PDoS) and False Endorsement-based DoS (FEDoS) attacks. In this paper, a scheme, called AAD, is proposed to Acquire Authentic Data in UWSNs. We exploit the collaboration among sensors to address the authentication problem. With the proper design of the collaboration mechanism, AAD has superior resilience against sensor compromises, PDoS attack, and FEDoS attack. In addition, compared with prior works, AAD also has relatively low energy consumption. In particular, according to our simulation, in a network with 1,000 sensors, the energy consumed by AAD is lower than 30% of that consumed by the existing method, ExCo. The analysis and simulation are also conducted to demonstrate the superiority of the proposed AAD scheme over the existing methods

Secure Precise Clock Synchronization for Interconnected Body Area Networks

Secure time synchronization is a paramount service for wireless sensor networks (WSNs) constituted by multiple interconnected body area networks (BANs). We propose a novel approach to securely and efficiently synchronize nodes at BAN level and/or WSN level. Each BAN develops its own notion of time. To this effect, the nodes of a BAN synchronize with their BAN controller node. Moreover, controller nodes of different BANs cooperate to agree on a WSN global and/or to transfer UTC time. To reduce the number of exchanged synchronization messages, we use an environmental-aware time prediction algorithm. The performance analysis in this paper shows that our approach exhibits very advanced security, accuracy, precision, and low-energy trade-off. For comparable precision, our proposal outstands related clock synchronization protocols in energy efficiency and risk of attacks. These results are based on computations

Semantics-Preserving Implementation of Synchronous Specifications Over Dynamic TDMA Distributed Architectures

International audienceWe propose a technique to automatically synthesize programs and schedules for hard real-time distributed (embedded) systems from synchronous data-flow models. Our technique connects the SynDEx scheduling tool and the Network Code toolchain in a seamless flow of automatic model transformations that go all the way from specification to implementation. Our contribution is the non-trivial connection between the models manipulated by SynDEx and by the Network Code toolchain, at both formal and tool level. We provide an algorithm for converting the data-dependent schedule tables output by SynDEx into Network Code programs which can be seen as an ``assembly code'' level for time-driven distributed real-time systems. The main difficulty is to ensure the preservation of both functionality and the real-time guarantees computed by SynDEx in the presence of clock drifts (which are abstracted away in the scheduling model of SynDEx). Existing tools can convert the resulting Network Code programs into software and hardware-accelerated execution units.Nous proposons une technique pour la synthèse automatique de programmes et ordonnancements pour des systèmes temps-réel (embarqués) distribués, à partir de spécifications synchrones flot de données

Designing Robust Collaborative Services in Distributed Wireless Networks

Wireless Sensor Networks (WSNs) are a popular class of distributed collaborative networks finding suitability from medical to military applications. However, their vulnerability to capture, their "open" wireless interfaces, limited battery life, all result in potential vulnerabilities. WSN-based services inherit these vulnerabilities. We focus on tactical environments where sensor nodes play complex roles in data sensing, aggregation and decision making. Services in such environments demand a high level of reliability and robustness. The first problem we studied is robust target localization. Location information is important for surveillance, monitoring, secure routing, intrusion detection, on-demand services etc. Target localization means tracing the path of moving entities through some known surveillance area. In a tactical environment, an adversary can often capture nodes and supply incorrect surveillance data to the system. In this thesis we create a target localization protocol that is robust against large amounts of such falsified data. Location estimates are generated by a Bayesian maximum-likelihood estimator. In order to achieve improved results with respect to fraudulent data attacks, we introduce various protection mechanisms. Further, our novel approach of employing watchdog nodes improves our ability to detect anomalies reducing the impact of an adversarial attack and limiting the amount of falsified data that gets accepted into the system. By concealing and altering the location where data is aggregated, we restrict the adversary to making probabilistic "guess" attacks at best, and increase robustness further. By formulating the problem of robust node localization under adversarial settings and casting it as a multivariate optimization problem, we solve for the system design parameters that correspond to the optimal solution. Together this results in a highly robust protocol design. In order for any collaboration to succeed, collaborating entities must have the same relative sense of time. This ensures that any measurements, surveillance data, mission commands, etc will be processed in the same epoch they are intended to serve. In most cases, data disseminated in a WSN is transient in nature, and applies for a short period of time. New data routinely replaces old data. It is imperative that data be placed in its correct time context; therefore..

A Framework for Computer Vision Assisted Beamforming in Aperiodic Phased Arrays

Mobile networks, unmanned air vehicles (UAVs), and other dynamic wireless systems are prevalent in several widespread military and commercial applications due dynamic ability to adapt to an environment and commonly implemented autonomous control. Their mobility and dynamic reconfiguration create randomly dispersed networks that inherently give rise to significant electromagnetic challenges in collaborative applications such as beamforming. Conventional radio and communication systems overcome these challenges through designs that are highly structured with respect to frequency and are static in nature. Two inherent problems prevent collaborative electromagnetic capabilities in these disparate random geometrical systems: cognizance of node positioning and local synchronization of oscillators, phase, and information. This work proposes the combined use of image processing techniques and infrared depth-of-field sensing to detect and track node position in a phased array control framework for morphing clusters of randomly distributed antennas. This framework is presented and designed to uniquely identify array elements (or platforms) and track the motion-dynamic spatial distribution to provide feedback and control information for phase shifting and beamforming. A primary metric of this work is to examine the core performance of the phased array control system with respect to beamforming accuracy. This begins with the use of image recognition algorithms in a reconnaissance phase to establish element identities and determine their locations in the field of view. This process informs the depth-of-field sensor to prompt evaluation of the spatial distribution of elements and enable element location tracking through time. This information is communicated to a distributed array controller that identifies the characteristic function of the array (triangular, spheroidal, etc.), and calculates phases for the elements to achieve the desired beam steering operation. The framework also includes a mobile device (smartphone, tablet, etc.) as a user interface which can be used to control the phased array and link geolocation information for autonomous tracking modes. A framework operating at 2.48 GHz has been developed using low-cost off-the-shelf components, as well as custom-designed element platforms so the performance of the system can be observed experimentally. Results for element identification and spatial distribution are included to benchmark the accuracy of the aforementioned system. Next, a series of experiments demonstrates the operation of the proposed system through radiation patterns that incorporate beam steering and other complex control mechanisms. Analysis of the patterns shows from various geometrical topologies is presented to demonstrate the capability of the system to analyze morphing swarms and clusters. Finally, a conclusion presents findings from some noticeable differences in simulated and measured results