Antonio-Javier Garcia-Sanchez

Wireless Sensor Network Deployment for Monitoring Wildlife Passages

Wireless Sensor Networks (WSNs) are being deployed in very diverse application scenarios, including rural and forest environments. In these particular contexts, specimen protection and conservation is a challenge, especially in natural reserves, dangerous locations or hot spots of these reserves (i.e., roads, railways, and other civil infrastructures). This paper proposes and studies a WSN based system for generic target (animal) tracking in the surrounding area of wildlife passages built to establish safe ways for animals to cross transportation infrastructures. In addition, it allows target identification through the use of video sensors connected to strategically deployed nodes. This deployment is designed on the basis of the IEEE 802.15.4 standard, but it increases the lifetime of the nodes through an appropriate scheduling. The system has been evaluated for the particular scenario of wildlife monitoring in passages across roads. For this purpose, different schemes have been simulated in order to find the most appropriate network operational parameters. Moreover, a novel prototype, provided with motion detector sensors, has also been developed and its design feasibility demonstrated. Original software modules providing new functionalities have been implemented and included in this prototype. Finally, main performance evaluation results of the whole system are presented and discussed in depth.

A Comprehensive Approach to WSN-Based ITS Applications: A Survey

In order to perform sensing tasks, most current Intelligent Transportation Systems (ITS) rely on expensive sensors, which offer only limited functionality. A more recent trend consists of using Wireless Sensor Networks (WSN) for such purpose, which reduces the required investment and enables the development of new collaborative and intelligent applications that further contribute to improve both driving safety and traffic efficiency. This paper surveys the application of WSNs to such ITS scenarios, tackling the main issues that may arise when developing these systems. The paper is divided into sections which address different matters including vehicle detection and classification as well as the selection of appropriate communication protocols, network architecture, topology and some important design parameters. In addition, in line with the multiplicity of different technologies that take part in ITS, it does not consider WSNs just as stand-alone systems, but also as key components of heterogeneous systems cooperating along with other technologies employed in vehicular scenarios.

On Maximizing the Lifetime of Wireless Sensor Networks by Optimally Assigning Energy Supplies

The extension of the network lifetime of Wireless Sensor Networks (WSN) is an important issue that has not been appropriately solved yet. This paper addresses this concern and proposes some techniques to plan an arbitrary WSN. To this end, we suggest a hierarchical network architecture, similar to realistic scenarios, where nodes with renewable energy sources (denoted as primary nodes) carry out most message delivery tasks, and nodes equipped with conventional chemical batteries (denoted as secondary nodes) are those with less communication demands. The key design issue of this network architecture is the development of a new optimization framework to calculate the optimal assignment of renewable energy supplies (primary node assignment) to maximize network lifetime, obtaining the minimum number of energy supplies and their node assignment. We also conduct a second optimization step to additionally minimize the number of packet hops between the source and the sink. In this work, we present an algorithm that approaches the results of the optimization framework, but with much faster execution speed, which is a good alternative for large-scale WSN networks. Finally, the network model, the optimization process and the designed algorithm are further evaluated and validated by means of computer simulation under realistic conditions. The results obtained are discussed comparatively.

Current Trends in Wireless Mesh Sensor Networks: A Review of Competing Approaches

Finding a complete mesh-based solution for low-rate wireless personal area networks (LR-WPANs) is still an open issue. To cope with this concern, different competing approaches have emerged in the Wireless Mesh Sensor Networks (WMSNs) field in the last few years. They are usually supported by the IEEE 802.15.4 standard, the most commonly adopted LR-WPAN recommendation for point-to-point topologies. In this work, we review the most relevant and up-to-date WMSN solutions that extend the IEEE 802.15.4 standard to multi-hop mesh networks. To conduct this review, we start by identifying the most significant WMSN requirements (i.e., interoperability, robustness, scalability, mobility or energy-efficiency) that reveal the benefits and shortcomings of each proposal. Then, we re-examine thoroughly the group of proposals following different design guidelines which are usually considered by end-users and developers. Among all of the approaches reviewed, we highlight the IEEE 802.15.5 standard, a recent recommendation that, in its LR-WPAN version, fully satisfies the greatest number of WMSN requirements. As a result, IEEE 802.15.5 can be an appropriate solution for a wide-range of applications, unlike the majority of the remaining solutions reviewed, which are usually designed to solve particular problems, for instance in the home, building and industrial sectors. In this sense, a description of IEEE 802.15.5 is also included, paying special attention to its efficient energy-saving mechanisms. Finally, possible improvements of this recommendation are pointed out in order to offer hints for future research.

A cross-layer solution for enabling real-time video transmission over IEEE 802.15.4 networks

Over the last few years, the research community has devoted great attention to video transmission on wireless sensor networks, and in particular to their recent evolution, the one based on IEEE 802.15.4 standard. This cost-efficient wireless technology is aimed at transmitting information at low rates and short distances. Extending the use of this technology for intensive bandwidth applications is a challenge that offers the opportunity to support value-added services. This paper deals with this issue and evaluates, by analysis and computer simulation as well as by developing a first prototype, the feasibility of transmitting MPEG-4 video information over an IEEE 802.15.4 network. The study of power-consumption is also considered and so are the Quality of Service parameters together with the human quality perception of the received video streaming. A detailed cross-layer solution is offered, and the results obtained are presented and discussed.

A Comprehensive WSN-Based Approach to Efficiently Manage a Smart Grid

The Smart Grid (SG) is conceived as the evolution of the current electrical grid representing a big leap in terms of efficiency, reliability and flexibility compared to todays electrical network. To achieve this goal, the Wireless Sensor Networks (WSNs) are considered by the scientific/engineering community to be one of the most suitable technologies to apply SG technology to due to their low-cost, collaborative and long-standing nature. However, the SG has posed significant challenges to utility operators—mainly very harsh radio propagation conditions and the lack of appropriate systems to empower WSN devices—making most of the commercial widespread solutions inadequate. In this context, and as a main contribution, we have designed a comprehensive ad-hoc WSN-based solution for the Smart Grid (SENSED-SG) that focuses on specific implementations of the MAC, the network and the application layers to attain maximum performance and to successfully deal with any arising hurdles. Our approach has been exhaustively evaluated by computer simulations and mathematical analysis, as well as validation within real test-beds deployed in controlled environments. In particular, these test-beds cover two of the main scenarios found in a SG; on one hand, an indoor electrical substation environment, implemented in a High Voltage AC/DC laboratory, and, on the other hand, an outdoor case, deployed in the Transmission and Distribution segment of a power grid. The results obtained show that SENSED-SG performs better and is more suitable for the Smart Grid than the popular ZigBee WSN approach.

Feasibility Study of MPEG-4 Transmission on IEEE 802.15.4 Networks

IEEE 802.15.4 is a wireless technology aimed at the transmission of information at low rates and short distances. Therefore, the expected traffic carried by these networks is one whose transmission rates are low, i.e. information captured by sensors. The extension of this technology to higher data rates is a challenge that gives us the opportunity to support additional services. This paper deals with this issue and evaluates the feasibility of transmitting MPEG-4 video information by computer simulation. Another subject to take into consideration is the computation of the human quality perception when the video streaming is received. To achieve these objectives, the GTS slots of the IEEE 802.15.4 MAC are implemented in the currently available simulation tools. The results obtained are also presented and discussed.

On the role of wireless sensor networks in intelligent transportation systems

Currently Vehicular Ad-hoc Networks (VANET) are receiving great attention by researchers because of their potentiality for developing innovative applications in the Intelligent Transportation Systems (ITS) context and are expected to be a widely adopted technology in the medium/long term. However, for the near future, the adoption of this technology is difficult since its performance relies excessively on its penetration rate into vehicles. In addition VANET are only able to gather information about the road while vehicles equipped with the appropriate technology are nearby, otherwise information can only be obtained by expensive and therefore scarcely deployed Roadside Units (RSU). Wireless Sensor Networks (WSN), on the contrary, can be deployed along a road (or in a parking lot area) with very little installation and maintenance costs. They can be used to constantly acquire information related to the road condition and the traffic state and, in addition, execute collaborative in-road processing for safety purposes. These properties make WSN an effective complement to VANET, since they can cooperate with them in order to mitigate their limitations. On the other hand, WSN deployments can also benefit from VANET and other communication technologies such as cellular networks in order to disseminate the information gathered to distant places. Consequently, WSN can also play a major role in ITS.

On the optimization of wireless multimedia sensor networks: A goal programming approach

Network lifetime is a crucial concern for Wireless Multimedia Sensor Networks (WMSNs), particularly due to the energy constraints of their nodes and the significant bitrate required by multimedia applications. This paper deals with this issue, studying how to achieve the maximum network lifetime, and simultaneously satisfying the best aggregate throughput for the multimedia services offered. To this end, we propose a planning model that results in a more accurate solution for an arbitrary network deployment than using the current optimization techniques applied both to WMSNs and traditional Wireless Sensor Networks (WSNs). Our model is based on multi-objective formulation and goal programming, which, to the best of our knowledge, have never been employed in the WSN field. This paper also proposes a load balancing algorithm which ensures a fair traffic load distribution per link during the network operation and matches the values returned by the mathematical planning model for the set lifetime and throughput. Simulation results are presented and further discussed to show the effectiveness of the numerical solutions. Finally, a test-bed deployed in a trial environment validates the theoretical contributions of this work.

On the synchronization of IEEE 802.15.5 wireless mesh sensor networks: Shortcomings and improvements

As part of the recent IEEE 802.15.5 wireless mesh sensor networks (WMSN) standard, Synchronous Energy Saving (SES) is planned to provide energy savings to scheduled communications with strict temporal requirements that, a priori, facilitate the development of delay-sensitive applications. It is accomplished by means of different mechanisms, among which we highlight a straightforward synchronization process. However, the SES synchronization scheme introduces variable delays in the dissemination of information and reduces the lifetime of the nodes and the entire network significantly, thus limiting the full exploitation of SES. This article presents a new synchronization approach, that we call High-PerformanceSynchronization Algorithm for wireless mesh sensor networks (HIPESYN), which is adapted to the IEEE 802.15.5 standard for synchronous communications. HIPESYN supports intensive bandwidth applications in a much better way than with the original design. The proposed algorithm is also thoroughly evaluated and its results carefully discussed.