Joan Garcia-Haro

Tracking of Returnable Packaging and Transport Units with active RFID in the grocery supply chain

The fresh products supply chain still has room to improve and increase efficiency and even become an intelligent supply chain by means of automating simple but valuable data flows which will be the foundations and first stage for developing new value-added services. The Spanish company ECOMOVISTAND has developed an innovative and ecological packaging and transport unit, called MT, for the grocery supply chain, which can be used in the entire product cycle; that is, the MT serves (1) as packaging at the producer, (2) as transport unit, (3) as storage at warehouses, and (4) as display stand at the supermarket, all in the same mechanical system, being thus a Returnable Packaging and Transport Unit. An MT needs the support of information technologies to achieve its true potential. In this paper we show the work developed in collaboration with ECOMOVISTAND in order to turn the MT into an intelligent product platform by embedding Active RFID tags. Data flows are integrated into an information system, called MEGASTAND, which allows to track MTs over the entire supply chain and provide value-added services to the customers.

Technical Communication: Angle-of-arrival localization based on antenna arrays for wireless sensor networks

Among the large number of contributions concerning the localization techniques for wireless sensor networks (WSNs), there is still no simple, energy and cost efficient solution suitable in outdoor scenarios. In this paper, a technique based on antenna arrays and angle-of-arrival (AoA) measurements is carefully discussed. While the AoA algorithms are rarely considered for WSNs due to the large dimensions of directional antennas, some system configurations are investigated that can be easily incorporated in pocket-size wireless devices. A heuristic weighting function that enables decreasing the location errors is introduced. Also, the detailed performance analysis of the presented system is provided. The localization accuracy is validated through realistic Monte-Carlo simulations that take into account the specificity of propagation conditions in WSNs as well as the radio noise effects. Finally, trade-offs between the accuracy, localization time and the number of anchors in a network are addressed.

Simulation scalability issues in wireless sensor networks

The formidable growth of WSN research has opened challenging issues about their performance evaluation. Despite the steady increase in mathematical analysis and experimental deployments, most of the community has chosen simulation for their study. Although it seems straightforward, this approach becomes quite a delicate matter. Complexity is caused by several issues. First, the large number of nodes heavily impacts simulation performance and scalability. Second, credible results demand an accurate characterization of the sensor radio channel. New aspects inherent in WSN must be included in simulators (e.g., a physical environment and an energy model), leading to different degrees of accuracy vs. performance. Moreover, many necessary models are in the continuous time domain (e.g., heat transmission, battery discharge), and thus complex to integrate into discrete event network simulators. These issues result in exponential growth of overall network state information. Through this survey we review these problems both quantitatively and qualitatively while depicting a common suitable simulation model. We also briefly describe the most significant simulation frameworks available.

An accurate radio channel model for wireless sensor networks simulation

Simulations are currently an essential tool to develop and test wireless sensor networks (WSNs) protocols and to analyze future WSNs applications performance. Researchers often simulate their proposals rather than deploying high-cost test-beds or develop complex mathematical analysis. However, simulation results rely on physical layer assumptions, which are not usually accurate enough to capture the real behavior of a WSN. Such an issue can lead to mistaken or questionable results. Besides, most of the envisioned applications for WSNs consider the nodes to be at the ground level. However, there is a lack of radio propagation characterization and validation by measurements with nodes at ground level for actual sensor hardware. In this paper, we propose to use a low-computational cost, two slope, log-normal path-loss near ground outdoor channel model at 868 MHz in WSN simulations. The model is validated by extensive real hardware measurements obtained in different scenarios. In addition, accurate model parameters are provided. This model is compared with the well-known one slope path-loss model. We demonstrate that the two slope log-normal model provides more accurate WSN simulations at almost the same computational cost as the single slope one. It is also shown that the radio propagation characterization heavily depends on the adjusted model parameters for a target deployment scenario: The model parameters have a considerable impact on the average number of neighbors and on the network connectivity.

Wireless communications deployment in industry: a review of issues, options and technologies

Present basis of knowledge management is the efficient share of information. The challenges that modern industrial processes have to face are multimedia information gathering and system integration, through large investments and adopting new technologies. Driven by a notable commercial interest, wireless networks like GSM or IEEE 802.11 are now the focus of industrial attention, because they provide numerous benefits, such as low cost, fast deployment and the ability to develop new applications. However, wireless nets must satisfy industrial requisites: scalability, flexibility, high availability, immunity to interference, security and many others that are crucial in hazardous and noisy environments. This paper presents a thorough survey of all this requirements, reviews the existing wireless solutions, and explores possible matching between industry and the current existing wireless standards.

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.

Control-based scheduling with QoS support for vehicle to infrastructure communications

This article is focused on data transmission scheduling in V2I communications, where a central station, the roadside beacon, decides how to allocate system resources among the vehicles under coverage. We consider non-safety applications whose commercial appeal is expected to accelerate the deployment of VANETs. In this case the main objective is to deliver as much information as possible during the connection lifetime of the vehicles, which is limited by their speed and the length of the road sections under coverage. In this environment the contention free poll-based access mechanism of the 802.11e standard included in current VANET specifications is especially suitable. The design of a scheduling mechanism is addressed in this article from a control theory point of view with the additional novelty of using an optimal control formulation comprising resource constraints. This design strategy allows QoS differentiation, assuring a fixed amount of bandwidth for each QoS class. The resulting algorithm not only maximizes the amount of data delivered, but also reduces performance differences between users traveling along different roads.

Offline Impairment Aware RWA Algorithms for Cross-Layer Planning of Optical Networks

Transparent optical networks are the enabling infrastructure for converged multi-granular networks in the future Internet. The cross-layer planning of these networks considers physical impairments in the network layer design. This is complicated by the diversity of modulation formats, transmission rates, amplification and compensation equipments, or deployed fiber links. Thereby, the concept of quality of transmission (QoT) attempts to embrace the effects of the physical layer impairments, to introduce them in a multi-criterium optimization and planning process. This paper contributes in this field by the proposal and comparative evaluation of two novel offline impairment aware planning algorithms for transparent optical networks, which share a common QoT evaluation function. The first algorithm is based on an iterative global search driven by a set of binary integer linear programming formulations. Heuristic techniques are included to limit the binary programming complexity. The second algorithm performs different pre-orderings of the lightpath demand, followed by a sequential processing of the lightpath demands. The performance and the scalability of both approaches are investigated. Results reveal great scalability properties of the global search algorithm, and a performance similar to or better than the sequential schemes.

Performance evaluation of MAC transmission power control in wireless sensor networks

In this paper we provide a method to analytically compute the energy saving provided by the use of transmission power control (TPC) at the MAC layer in wireless sensor networks (WSN). We consider a classical TPC mechanism: data packets are transmitted with the minimum power required to achieve a given packet error probability, whereas the additional MAC control packets are transmitted with the nominal (maximum) power. This scheme has been chosen because it does not modify the network topology, since control packet transmission range does not change. This property also allows us to analytically compute the expected energy savings. Besides, this type of TPC can be implemented in the current sensor hardware, and it can be directly applied to several MAC protocols already proposed for WSN. The foundation of our analysis is the evaluation of L ratio, defined as the total energy consumed by the network using the original MAC protocol divided by the total energy consumed if the TPC mechanism is employed. In the L computation we emphasize the basic properties of sensor networks. Namely, the savings are calculated for a network that is active for a very long time, and where the number of sensors is supposed to be very large. The nodes position is assumed to be random - a normal bivariate distribution is assumed in the paper - and no node mobility is considered. In the analysis we stress the radio propagation and the distribution of the nodes in the network, which will ultimately determine the performance of the TPC. Under these conditions we compute the mean value of L. Finally, we have applied the method to evaluate the benefits of TPC for TDMA and CSMA with two representative protocols, L-MAC and S-MAC using their implementation reference parameters. The conclusion is that, while S-MAC does not achieve a significant improvement, L-MAC may reach energy savings up to 10-20%.