E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Special Issue "Sensors and Smart Cities"

Quicklinks

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Sensor Networks".

Deadline for manuscript submissions: closed (30 April 2015)

Special Issue Editors

Guest Editor
Prof. Dr. Antonio Puliafito

Dipartimento di Ingegneria Civile, Informatica, Edile, Ambientale e Matematica Applicata (DICIEAMA), Università di Messina, Italy
Website | E-Mail
Interests: System modelling and Performance evaluation; Reliability and fault tolerance; Multimedia systems; Wireless and RFID systems; GRID and Cloud computing
Guest Editor
Prof. Dr. Symeon Papavassiliou

School of Electrical and Computer Engineering, National Technical University of Athens Iroon Polytechniou 9 Athens, 15780, Greece
Website | E-Mail
Interests: complex networks; wireless systems; ad hoc and sensor networks; performance evaluation of stochastic systems; on-line social networks
Guest Editor
Prof. Dr. Dario Bruneo

Dipartimento di Ingegneria Civile, Informatica, Edile, Ambientale e Matematica Applicata (DICIEAMA), Università di Messina, Italy
Website | E-Mail
Interests: Distributed systems, wireless sensor networks, IoT, performance evaluation

Special Issue Information

Dear Colleagues,

A smart city represents an improvement of today’s cities both functionally and structurally, that strategically utilizes many smart factors, such as Information and Communications Technology (ICT), to increase the city’s sustainable growth and strengthen city functions, while ensuring citizens’ quality of life and health. Cities can be viewed as a microcosm of “objects” with which citizens interact daily: street furniture, public buildings, transportation, monuments, public lighting and much more. Moreover, a continuous monitoring of a city’s status occurs through sensors and processors applied within the real-world infrastructure. The Internet of Things (IoT) concept imagines all these objects being “smart”, connected to the Internet, and able to communicate with each other and with the external environment, interacting and sharing data and information. Each object in the IoT can be both the collector and distributor of information regarding mobility, energy consumption, air pollution as well as potentially offering cultural and tourist information. As a consequence, cyber and real worlds are strongly linked in a smart city. New services can be deployed when needed and evaluation mechanisms will be set up to assess the health and success of a smart city.

The aim of this Special Issue is to bring together innovative developments in areas related to sensors and smart cities, including, but not limited to:

  • computing and sensing infrastructures;
  • cost (of node, energy, development, deployment, maintenance);
  • communication (security, resilience, low energy);
  • adaptability (to environment, energy, faults);
  • data processing (on nodes, distributed, aggregation, discovery, big data);
  • self-learning (pattern discovery, prediction, auto-configuration);
  • deployment (cost, error prevention, localization);
  • maintenance (troubleshooting, recurrent costs);
  • applications (both new and enjoying new life);
  • smart users experience;
  • trust and privacy;
  • crowdsourcing, crowdsensing, participatory sensing;
  • cognition and awareness;
  • cyber-physical systems.

Both review articles and original research papers relating to sensors and smart cities are solicited. There is particular interest for papers with advances towards practical experiences and services overcoming the adoption barriers for sensors and smart cities.

Prof. Dr. Antonio Puliafito
Prof. Dr. Symeon Papavassiliou
Prof. Dr. Dario Bruneo
Guest Editors

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).


Keywords

  • sensors
  • distributed computing
  • internet of things
  • interconnected objects
  • cyber-physical systems
  • complex networks
  • applications in smart cities
  • computing and sensing infrastructures

Published Papers (36 papers)

View options order results:
result details:
Displaying articles 1-36
Export citation of selected articles as:

Research

Jump to: Review

Open AccessArticle Development of a Conductivity Sensor for Monitoring Groundwater Resources to Optimize Water Management in Smart City Environments
Sensors 2015, 15(9), 20990-21015; doi:10.3390/s150920990
Received: 13 May 2015 / Revised: 10 August 2015 / Accepted: 19 August 2015 / Published: 26 August 2015
Cited by 3 | PDF Full-text (1186 KB) | HTML Full-text | XML Full-text
Abstract
The main aim of smart cities is to achieve the sustainable use of resources. In order to make the correct use of resources, an accurate monitoring and management is needed. In some places, like underground aquifers, access for monitoring can be difficult, therefore
[...] Read more.
The main aim of smart cities is to achieve the sustainable use of resources. In order to make the correct use of resources, an accurate monitoring and management is needed. In some places, like underground aquifers, access for monitoring can be difficult, therefore the use of sensors can be a good solution. Groundwater is very important as a water resource. Just in the USA, aquifers represent the water source for 50% of the population. However, aquifers are endangered due to the contamination. One of the most important parameters to monitor in groundwater is the salinity, as high salinity levels indicate groundwater salinization. In this paper, we present a specific sensor for monitoring groundwater salinization. The sensor is able to measure the electric conductivity of water, which is directly related to the water salinization. The sensor, which is composed of two copper coils, measures the magnetic field alterations due to the presence of electric charges in the water. Different salinities of the water generate different alterations. Our sensor has undergone several tests in order to obtain a conductivity sensor with enough accuracy. First, several prototypes are tested and are compared with the purpose of choosing the best combination of coils. After the best prototype was selected, it was calibrated using up to 30 different samples. Our conductivity sensor presents an operational range from 0.585 mS/cm to 73.8 mS/cm, which is wide enough to cover the typical range of water salinities. With this work, we have demonstrated that it is feasible to measure water conductivity using solenoid coils and that this is a low cost application for groundwater monitoring. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Visual Sensing for Urban Flood Monitoring
Sensors 2015, 15(8), 20006-20029; doi:10.3390/s150820006
Received: 21 May 2015 / Revised: 21 May 2015 / Accepted: 10 August 2015 / Published: 14 August 2015
Cited by 1 | PDF Full-text (7467 KB) | HTML Full-text | XML Full-text
Abstract
With the increasing climatic extremes, the frequency and severity of urban flood events have intensified worldwide. In this study, image-based automated monitoring of flood formation and analyses of water level fluctuation were proposed as value-added intelligent sensing applications to turn a passive monitoring
[...] Read more.
With the increasing climatic extremes, the frequency and severity of urban flood events have intensified worldwide. In this study, image-based automated monitoring of flood formation and analyses of water level fluctuation were proposed as value-added intelligent sensing applications to turn a passive monitoring camera into a visual sensor. Combined with the proposed visual sensing method, traditional hydrological monitoring cameras have the ability to sense and analyze the local situation of flood events. This can solve the current problem that image-based flood monitoring heavily relies on continuous manned monitoring. Conventional sensing networks can only offer one-dimensional physical parameters measured by gauge sensors, whereas visual sensors can acquire dynamic image information of monitored sites and provide disaster prevention agencies with actual field information for decision-making to relieve flood hazards. The visual sensing method established in this study provides spatiotemporal information that can be used for automated remote analysis for monitoring urban floods. This paper focuses on the determination of flood formation based on image-processing techniques. The experimental results suggest that the visual sensing approach may be a reliable way for determining the water fluctuation and measuring its elevation and flood intrusion with respect to real-world coordinates. The performance of the proposed method has been confirmed; it has the capability to monitor and analyze the flood status, and therefore, it can serve as an active flood warning system. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle On the Optimization of a Probabilistic Data Aggregation Framework for Energy Efficiency in Wireless Sensor Networks
Sensors 2015, 15(8), 19597-19617; doi:10.3390/s150819597
Received: 28 January 2015 / Revised: 15 May 2015 / Accepted: 5 August 2015 / Published: 11 August 2015
PDF Full-text (2002 KB) | HTML Full-text | XML Full-text
Abstract
Among the key aspects of the Internet of Things (IoT) is the integration of heterogeneous sensors in a distributed system that performs actions on the physical world based on environmental information gathered by sensors and application-related constraints and requirements. Numerous applications of Wireless
[...] Read more.
Among the key aspects of the Internet of Things (IoT) is the integration of heterogeneous sensors in a distributed system that performs actions on the physical world based on environmental information gathered by sensors and application-related constraints and requirements. Numerous applications of Wireless Sensor Networks (WSNs) have appeared in various fields, from environmental monitoring, to tactical fields, and healthcare at home, promising to change our quality of life and facilitating the vision of sensor network enabled smart cities. Given the enormous requirements that emerge in such a setting—both in terms of data and energy—data aggregation appears as a key element in reducing the amount of traffic in wireless sensor networks and achieving energy conservation. Probabilistic frameworks have been introduced as operational efficient and performance effective solutions for data aggregation in distributed sensor networks. In this work, we introduce an overall optimization approach that improves and complements such frameworks towards identifying the optimal probability for a node to aggregate packets as well as the optimal aggregation period that a node should wait for performing aggregation, so as to minimize the overall energy consumption, while satisfying certain imposed delay constraints. Primal dual decomposition is employed to solve the corresponding optimization problem while simulation results demonstrate the operational efficiency of the proposed approach under different traffic and topology scenarios. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Scalable and Cost-Effective Assignment of Mobile Crowdsensing Tasks Based on Profiling Trends and Prediction: The ParticipAct Living Lab Experience
Sensors 2015, 15(8), 18613-18640; doi:10.3390/s150818613
Received: 16 May 2015 / Revised: 19 July 2015 / Accepted: 24 July 2015 / Published: 30 July 2015
Cited by 1 | PDF Full-text (992 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, sensor-rich smartphones potentially enable the harvesting of huge amounts of valuable sensing data in urban environments, by opportunistically involving citizens to play the role of mobile virtual sensors to cover Smart City areas of interest. This paper proposes an in-depth study of
[...] Read more.
Nowadays, sensor-rich smartphones potentially enable the harvesting of huge amounts of valuable sensing data in urban environments, by opportunistically involving citizens to play the role of mobile virtual sensors to cover Smart City areas of interest. This paper proposes an in-depth study of the challenging technical issues related to the efficient assignment of Mobile Crowd Sensing (MCS) data collection tasks to volunteers in a crowdsensing campaign. In particular, the paper originally describes how to increase the effectiveness of the proposed sensing campaigns through the inclusion of several new facilities, including accurate participant selection algorithms able to profile and predict user mobility patterns, gaming techniques, and timely geo-notification. The reported results show the feasibility of exploiting profiling trends/prediction techniques from volunteers’ behavior; moreover, they quantitatively compare different MCS task assignment strategies based on large-scale and real MCS data campaigns run in the ParticipAct living lab, an ongoing MCS real-world experiment that involved more than 170 students of the University of Bologna for more than one year. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle V-Alert: Description and Validation of a Vulnerable Road User Alert System in the Framework of a Smart City
Sensors 2015, 15(8), 18480-18505; doi:10.3390/s150818480
Received: 27 April 2015 / Revised: 15 July 2015 / Accepted: 24 July 2015 / Published: 29 July 2015
Cited by 2 | PDF Full-text (3165 KB) | HTML Full-text | XML Full-text
Abstract
V-Alert is a cooperative application to be deployed in the frame of Smart Cities with the aim of reducing the probability of accidents involving Vulnerable Road Users (VRU) and vehicles. The architecture of V-Alert combines short- and long-range communication technologies in order to
[...] Read more.
V-Alert is a cooperative application to be deployed in the frame of Smart Cities with the aim of reducing the probability of accidents involving Vulnerable Road Users (VRU) and vehicles. The architecture of V-Alert combines short- and long-range communication technologies in order to provide more time to the drivers and VRU to take the appropriate maneuver and avoid a possible collision. The information generated by mobile sensors (vehicles and cyclists) is sent over this heterogeneous communication architecture and processed in a central server, the Drivers Cloud, which is in charge of generating the messages that are shown on the drivers’ and cyclists’ Human Machine Interface (HMI). First of all, V-Alert has been tested in a simulated scenario to check the communications architecture in a complex scenario and, once it was validated, all the elements of V-Alert have been moved to a real scenario to check the application reliability. All the results are shown along the length of this paper. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Electrochemical Impedance Sensors for Monitoring Trace Amounts of NO3 in Selected Growing Media
Sensors 2015, 15(7), 17715-17727; doi:10.3390/s150717715
Received: 30 April 2015 / Revised: 27 June 2015 / Accepted: 9 July 2015 / Published: 21 July 2015
Cited by 2 | PDF Full-text (2718 KB) | HTML Full-text | XML Full-text
Abstract
With the advent of smart cities and big data, precision agriculture allows the feeding of sensor data into online databases for continuous crop monitoring, production optimization, and data storage. This paper describes a low-cost, compact, and scalable nitrate sensor based on electrochemical impedance
[...] Read more.
With the advent of smart cities and big data, precision agriculture allows the feeding of sensor data into online databases for continuous crop monitoring, production optimization, and data storage. This paper describes a low-cost, compact, and scalable nitrate sensor based on electrochemical impedance spectroscopy for monitoring trace amounts of NO3 in selected growing media. The nitrate sensor can be integrated to conventional microelectronics to perform online nitrate sensing continuously over a wide concentration range from 0.1 ppm to 100 ppm, with a response time of about 1 min, and feed data into a database for storage and analysis. The paper describes the structural design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the field testing of the nitrate sensor performed within tree nursery settings under ISO/IEC 17025 certifications. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Contextual Sensing: Integrating Contextual Information with Human and Technical Geo-Sensor Information for Smart Cities
Sensors 2015, 15(7), 17013-17035; doi:10.3390/s150717013
Received: 7 May 2015 / Revised: 25 June 2015 / Accepted: 29 June 2015 / Published: 14 July 2015
Cited by 4 | PDF Full-text (1149 KB) | HTML Full-text | XML Full-text
Abstract
In this article we critically discuss the challenge of integrating contextual information, in particular spatiotemporal contextual information, with human and technical sensor information, which we approach from a geospatial perspective. We start by highlighting the significance of context in general and spatiotemporal context
[...] Read more.
In this article we critically discuss the challenge of integrating contextual information, in particular spatiotemporal contextual information, with human and technical sensor information, which we approach from a geospatial perspective. We start by highlighting the significance of context in general and spatiotemporal context in particular and introduce a smart city model of interactions between humans, the environment, and technology, with context at the common interface. We then focus on both the intentional and the unintentional sensing capabilities of today’s technologies and discuss current technological trends that we consider have the ability to enrich human and technical geo-sensor information with contextual detail. The different types of sensors used to collect contextual information are analyzed and sorted into three groups on the basis of names considering frequently used related terms, and characteristic contextual parameters. These three groups, namely technical in situ sensors, technical remote sensors, and human sensors are analyzed and linked to three dimensions involved in sensing (data generation, geographic phenomena, and type of sensing). In contrast to other scientific publications, we found a large number of technologies and applications using in situ and mobile technical sensors within the context of smart cities, and surprisingly limited use of remote sensing approaches. In this article we further provide a critical discussion of possible impacts and influences of both technical and human sensing approaches on society, pointing out that a larger number of sensors, increased fusion of information, and the use of standardized data formats and interfaces will not necessarily result in any improvement in the quality of life of the citizens of a smart city. This article seeks to improve our understanding of technical and human geo-sensing capabilities, and to demonstrate that the use of such sensors can facilitate the integration of different types of contextual information, thus providing an additional, namely the geo-spatial perspective on the future development of smart cities. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Figures

Open AccessArticle A Smart City Lighting Case Study on an OpenStack-Powered Infrastructure
Sensors 2015, 15(7), 16314-16335; doi:10.3390/s150716314
Received: 14 May 2015 / Revised: 25 June 2015 / Accepted: 29 June 2015 / Published: 6 July 2015
Cited by 5 | PDF Full-text (1845 KB) | HTML Full-text | XML Full-text
Abstract
The adoption of embedded systems, mobile devices and other smart devices keeps rising globally, and the scope of their involvement broadens, for instance, in smart city-like scenarios. In light of this, a pressing need emerges to tame such complexity and reuse as much
[...] Read more.
The adoption of embedded systems, mobile devices and other smart devices keeps rising globally, and the scope of their involvement broadens, for instance, in smart city-like scenarios. In light of this, a pressing need emerges to tame such complexity and reuse as much tooling as possible without resorting to vertical ad hoc solutions, while at the same time taking into account valid options with regard to infrastructure management and other more advanced functionalities. Existing solutions mainly focus on core mechanisms and do not allow one to scale by leveraging infrastructure or adapt to a variety of scenarios, especially if actuators are involved in the loop. A new, more flexible, cloud-based approach, able to provide device-focused workflows, is required. In this sense, a widely-used and competitive framework for infrastructure as a service, such as OpenStack, with its breadth in terms of feature coverage and expanded scope, looks to fit the bill, replacing current application-specific approaches with an innovative application-agnostic one. This work thus describes the rationale, efforts and results so far achieved for an integration of IoT paradigms and resource ecosystems with such a kind of cloud-oriented device-centric environment, by focusing on a smart city scenario, namely a park smart lighting example, and featuring data collection, data visualization, event detection and coordinated reaction, as example use cases of such integration. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Figures

Open AccessArticle Smart City Mobility Application—Gradient Boosting Trees for Mobility Prediction and Analysis Based on Crowdsourced Data
Sensors 2015, 15(7), 15974-15987; doi:10.3390/s150715974
Received: 30 April 2015 / Revised: 22 June 2015 / Accepted: 29 June 2015 / Published: 3 July 2015
Cited by 6 | PDF Full-text (1829 KB) | HTML Full-text | XML Full-text
Abstract
Mobility management represents one of the most important parts of the smart city concept. The way we travel, at what time of the day, for what purposes and with what transportation modes, have a pertinent impact on the overall quality of life in
[...] Read more.
Mobility management represents one of the most important parts of the smart city concept. The way we travel, at what time of the day, for what purposes and with what transportation modes, have a pertinent impact on the overall quality of life in cities. To manage this process, detailed and comprehensive information on individuals’ behaviour is needed as well as effective feedback/communication channels. In this article, we explore the applicability of crowdsourced data for this purpose. We apply a gradient boosting trees algorithm to model individuals’ mobility decision making processes (particularly concerning what transportation mode they are likely to use). To accomplish this we rely on data collected from three sources: a dedicated smartphone application, a geographic information systems-based web interface and weather forecast data collected over a period of six months. The applicability of the developed model is seen as a potential platform for personalized mobility management in smart cities and a communication tool between the city (to steer the users towards more sustainable behaviour by additionally weighting preferred suggestions) and users (who can give feedback on the acceptability of the provided suggestions, by accepting or rejecting them, providing an additional input to the learning process). Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Providing IoT Services in Smart Cities through Dynamic Augmented Reality Markers
Sensors 2015, 15(7), 16083-16104; doi:10.3390/s150716083
Received: 21 April 2015 / Revised: 14 June 2015 / Accepted: 25 June 2015 / Published: 3 July 2015
Cited by 2 | PDF Full-text (12123 KB) | HTML Full-text | XML Full-text
Abstract
Smart cities are expected to improve the quality of life of citizens by relying on new paradigms, such as the Internet of Things (IoT) and its capacity to manage and interconnect thousands of sensors and actuators scattered across the city. At the same
[...] Read more.
Smart cities are expected to improve the quality of life of citizens by relying on new paradigms, such as the Internet of Things (IoT) and its capacity to manage and interconnect thousands of sensors and actuators scattered across the city. At the same time, mobile devices widely assist professional and personal everyday activities. A very good example of the potential of these devices for smart cities is their powerful support for intuitive service interfaces (such as those based on augmented reality (AR)) for non-expert users. In our work, we consider a scenario that combines IoT and AR within a smart city maintenance service to improve the accessibility of sensor and actuator devices in the field, where responsiveness is crucial. In it, depending on the location and needs of each service, data and commands will be transported by an urban communications network or consulted on the spot. Direct AR interaction with urban objects has already been described; it usually relies on 2D visual codes to deliver object identifiers (IDs) to the rendering device to identify object resources. These IDs allow information about the objects to be retrieved from a remote server. In this work, we present a novel solution that replaces static AR markers with dynamic markers based on LED communication, which can be decoded through cameras embedded in smartphones. These dynamic markers can directly deliver sensor information to the rendering device, on top of the object ID, without further network interaction. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle On the Design of Smart Parking Networks in the Smart Cities: An Optimal Sensor Placement Model
Sensors 2015, 15(7), 15443-15467; doi:10.3390/s150715443
Received: 1 May 2015 / Revised: 10 June 2015 / Accepted: 23 June 2015 / Published: 30 June 2015
Cited by 4 | PDF Full-text (773 KB) | HTML Full-text | XML Full-text
Abstract
Smart parking is a typical IoT application that can benefit from advances in sensor, actuator and RFID technologies to provide many services to its users and parking owners of a smart city. This paper considers a smart parking infrastructure where sensors are laid
[...] Read more.
Smart parking is a typical IoT application that can benefit from advances in sensor, actuator and RFID technologies to provide many services to its users and parking owners of a smart city. This paper considers a smart parking infrastructure where sensors are laid down on the parking spots to detect car presence and RFID readers are embedded into parking gates to identify cars and help in the billing of the smart parking. Both types of devices are endowed with wired and wireless communication capabilities for reporting to a gateway where the situation recognition is performed. The sensor devices are tasked to play one of the three roles: (1) slave sensor nodes located on the parking spot to detect car presence/absence; (2) master nodes located at one of the edges of a parking lot to detect presence and collect the sensor readings from the slave nodes; and (3) repeater sensor nodes, also called “anchor” nodes, located strategically at specific locations in the parking lot to increase the coverage and connectivity of the wireless sensor network. While slave and master nodes are placed based on geographic constraints, the optimal placement of the relay/anchor sensor nodes in smart parking is an important parameter upon which the cost and efficiency of the parking system depends. We formulate the optimal placement of sensors in smart parking as an integer linear programming multi-objective problem optimizing the sensor network engineering efficiency in terms of coverage and lifetime maximization, as well as its economic gain in terms of the number of sensors deployed for a specific coverage and lifetime. We propose an exact solution to the node placement problem using single-step and two-step solutions implemented in the Mosel language based on the Xpress-MPsuite of libraries. Experimental results reveal the relative efficiency of the single-step compared to the two-step model on different performance parameters. These results are consolidated by simulation results, which reveal that our solution outperforms a random placement in terms of both energy consumption, delay and throughput achieved by a smart parking network. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Location Privacy for Mobile Crowd Sensing through Population Mapping
Sensors 2015, 15(7), 15285-15310; doi:10.3390/s150715285
Received: 30 April 2015 / Revised: 18 June 2015 / Accepted: 19 June 2015 / Published: 29 June 2015
Cited by 4 | PDF Full-text (607 KB) | HTML Full-text | XML Full-text
Abstract
Opportunistic sensing allows applications to “task” mobile devices to measure context in a target region. For example, one could leverage sensor-equipped vehicles to measure traffic or pollution levels on a particular street or users’ mobile phones to locate (Bluetooth-enabled) objects in their vicinity.
[...] Read more.
Opportunistic sensing allows applications to “task” mobile devices to measure context in a target region. For example, one could leverage sensor-equipped vehicles to measure traffic or pollution levels on a particular street or users’ mobile phones to locate (Bluetooth-enabled) objects in their vicinity. In most proposed applications, context reports include the time and location of the event, putting the privacy of users at increased risk: even if identifying information has been removed from a report, the accompanying time and location can reveal sufficient information to de-anonymize the user whose device sent the report. We propose and evaluate a novel spatiotemporal blurring mechanism based on tessellation and clustering to protect users’ privacy against the system while reporting context. Our technique employs a notion of probabilistic k-anonymity; it allows users to perform local blurring of reports efficiently without an online anonymization server before the data are sent to the system. The proposed scheme can control the degree of certainty in location privacy and the quality of reports through a system parameter. We outline the architecture and security properties of our approach and evaluate our tessellation and clustering algorithm against real mobility traces. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Secure Routing Protocol for Wireless Sensor Networks Considering Secure Data Aggregation
Sensors 2015, 15(7), 15127-15158; doi:10.3390/s150715127
Received: 9 April 2015 / Revised: 5 June 2015 / Accepted: 19 June 2015 / Published: 26 June 2015
Cited by 4 | PDF Full-text (831 KB) | HTML Full-text | XML Full-text
Abstract
The commonly unattended and hostile deployments of WSNs and their resource-constrained sensor devices have led to an increasing demand for secure energy-efficient protocols. Routing and data aggregation receive the most attention since they are among the daily network routines. With the awareness of
[...] Read more.
The commonly unattended and hostile deployments of WSNs and their resource-constrained sensor devices have led to an increasing demand for secure energy-efficient protocols. Routing and data aggregation receive the most attention since they are among the daily network routines. With the awareness of such demand, we found that so far there has been no work that lays out a secure routing protocol as the foundation for a secure data aggregation protocol. We argue that the secure routing role would be rendered useless if the data aggregation scheme built on it is not secure. Conversely, the secure data aggregation protocol needs a secure underlying routing protocol as its foundation in order to be effectively optimal. As an attempt for the solution, we devise an energy-aware protocol based on LEACH and ESPDA that combines secure routing protocol and secure data aggregation protocol. We then evaluate its security effectiveness and its energy-efficiency aspects, knowing that there are always trade-off between both. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Citizen Sensors for SHM: Towards a Crowdsourcing Platform
Sensors 2015, 15(6), 14591-14614; doi:10.3390/s150614591
Received: 30 April 2015 / Revised: 12 June 2015 / Accepted: 16 June 2015 / Published: 19 June 2015
Cited by 8 | PDF Full-text (6919 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an innovative structural health monitoring (SHM) platform in terms of how it integrates smartphone sensors, the web, and crowdsourcing. The ubiquity of smartphones has provided an opportunity to create low-cost sensor networks for SHM. Crowdsourcing has given rise to citizen
[...] Read more.
This paper presents an innovative structural health monitoring (SHM) platform in terms of how it integrates smartphone sensors, the web, and crowdsourcing. The ubiquity of smartphones has provided an opportunity to create low-cost sensor networks for SHM. Crowdsourcing has given rise to citizen initiatives becoming a vast source of inexpensive, valuable but heterogeneous data. Previously, the authors have investigated the reliability of smartphone accelerometers for vibration-based SHM. This paper takes a step further to integrate mobile sensing and web-based computing for a prospective crowdsourcing-based SHM platform. An iOS application was developed to enable citizens to measure structural vibration and upload the data to a server with smartphones. A web-based platform was developed to collect and process the data automatically and store the processed data, such as modal properties of the structure, for long-term SHM purposes. Finally, the integrated mobile and web-based platforms were tested to collect the low-amplitude ambient vibration data of a bridge structure. Possible sources of uncertainties related to citizens were investigated, including the phone location, coupling conditions, and sampling duration. The field test results showed that the vibration data acquired by smartphones operated by citizens without expertise are useful for identifying structural modal properties with high accuracy. This platform can be further developed into an automated, smart, sustainable, cost-free system for long-term monitoring of structural integrity of spatially distributed urban infrastructure. Citizen Sensors for SHM will be a novel participatory sensing platform in the way that it offers hybrid solutions to transitional crowdsourcing parameters. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Managing Emergency Situations in the Smart City: The Smart Signal
Sensors 2015, 15(6), 14370-14396; doi:10.3390/s150614370
Received: 30 April 2015 / Revised: 3 June 2015 / Accepted: 8 June 2015 / Published: 18 June 2015
Cited by 2 | PDF Full-text (1983 KB) | HTML Full-text | XML Full-text
Abstract
In a city there are numerous items, many of them unnoticed but essential; this is the case of the signals. Signals are considered objects with reduced technological interest, but in this paper we prove that making them smart and integrating in the IoT
[...] Read more.
In a city there are numerous items, many of them unnoticed but essential; this is the case of the signals. Signals are considered objects with reduced technological interest, but in this paper we prove that making them smart and integrating in the IoT (Internet of Things) could be a relevant contribution to the Smart City. This paper presents the concept of Smart Signal, as a device conscious of its context, with communication skills, able to offer the best message to the user, and as a ubiquitous element that contributes with information to the city. We present the design considerations and a real implementation and validation of the system in one of the most challenging environments that may exist in a city: a tunnel. The main advantages of the Smart Signal are the improvement of the actual functionality of the signal providing new interaction capabilities with users and a new sensory mechanism of the Smart City. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Hands-On Experiences in Deploying Cost-Effective Ambient-Assisted Living Systems
Sensors 2015, 15(6), 14487-14512; doi:10.3390/s150614487
Received: 25 March 2015 / Revised: 13 June 2015 / Accepted: 15 June 2015 / Published: 18 June 2015
Cited by 2 | PDF Full-text (972 KB) | HTML Full-text | XML Full-text
Abstract
Older adults’ preferences to remain independent in their own homes along with the high costs of nursing home care have motivated the development of Ambient Assisted Living (AAL) technologies which aim at improving the safety, health conditions and wellness of the elderly. This
[...] Read more.
Older adults’ preferences to remain independent in their own homes along with the high costs of nursing home care have motivated the development of Ambient Assisted Living (AAL) technologies which aim at improving the safety, health conditions and wellness of the elderly. This paper reports hands-on experiences in designing, implementing and operating UbiCare, an AAL based prototype system for elderly home care monitoring. The monitoring is based on the recording of environmental parameters like temperature and light intensity as well as micro-level incidents which allows one to infer daily activities like moving, sitting, sleeping, usage of electrical appliances and plumbing components. The prototype is built upon inexpensive, off-the-shelf hardware (e.g., various sensors, Arduino microcontrollers, ZigBee-compatible wireless communication modules) and license-free software, thereby ensuring low system deployment costs. The network comprises nodes placed in a house’s main rooms or mounted on furniture, one wearable node, one actuator node and a centralized processing element (coordinator). Upon detecting significant deviations from the ordinary activity patterns of individuals and/or sudden falls, the system issues automated alarms which may be forwarded to authorized caregivers via a variety of communication channels. Furthermore, measured environmental parameters and activity incidents may be monitored through standard web interfaces. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Figures

Open AccessArticle Analysis of Intelligent Transportation Systems Using Model-Driven Simulations
Sensors 2015, 15(6), 14116-14141; doi:10.3390/s150614116
Received: 4 April 2015 / Revised: 27 May 2015 / Accepted: 10 June 2015 / Published: 15 June 2015
Cited by 4 | PDF Full-text (1200 KB) | HTML Full-text | XML Full-text
Abstract
Intelligent Transportation Systems (ITSs) integrate information, sensor, control, and communication technologies to provide transport related services. Their users range from everyday commuters to policy makers and urban planners. Given the complexity of these systems and their environment, their study in real settings is
[...] Read more.
Intelligent Transportation Systems (ITSs) integrate information, sensor, control, and communication technologies to provide transport related services. Their users range from everyday commuters to policy makers and urban planners. Given the complexity of these systems and their environment, their study in real settings is frequently unfeasible. Simulations help to address this problem, but present their own issues: there can be unintended mistakes in the transition from models to code; their platforms frequently bias modeling; and it is difficult to compare works that use different models and tools. In order to overcome these problems, this paper proposes a framework for a model-driven development of these simulations. It is based on a specific modeling language that supports the integrated specification of the multiple facets of an ITS: people, their vehicles, and the external environment; and a network of sensors and actuators conveniently arranged and distributed that operates over them. The framework works with a model editor to generate specifications compliant with that language, and a code generator to produce code from them using platform specifications. There are also guidelines to help researchers in the application of this infrastructure. A case study on advanced management of traffic lights with cameras illustrates its use. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Figures

Open AccessArticle Socially Aware Heterogeneous Wireless Networks
Sensors 2015, 15(6), 13705-13724; doi:10.3390/s150613705
Received: 30 April 2015 / Revised: 2 June 2015 / Accepted: 8 June 2015 / Published: 11 June 2015
Cited by 1 | PDF Full-text (8058 KB) | HTML Full-text | XML Full-text
Abstract
The development of smart cities has been the epicentre of many researchers’ efforts during the past decade. One of the key requirements for smart city networks is mobility and this is the reason stable, reliable and high-quality wireless communications are needed in order
[...] Read more.
The development of smart cities has been the epicentre of many researchers’ efforts during the past decade. One of the key requirements for smart city networks is mobility and this is the reason stable, reliable and high-quality wireless communications are needed in order to connect people and devices. Most research efforts so far, have used different kinds of wireless and sensor networks, making interoperability rather difficult to accomplish in smart cities. One common solution proposed in the recent literature is the use of software defined networks (SDNs), in order to enhance interoperability among the various heterogeneous wireless networks. In addition, SDNs can take advantage of the data retrieved from available sensors and use them as part of the intelligent decision making process contacted during the resource allocation procedure. In this paper, we propose an architecture combining heterogeneous wireless networks with social networks using SDNs. Specifically, we exploit the information retrieved from location based social networks regarding users’ locations and we attempt to predict areas that will be crowded by using specially-designed machine learning techniques. By recognizing possible crowded areas, we can provide mobile operators with recommendations about areas requiring datacell activation or deactivation. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Computational Architecture Based on RFID Sensors for Traceability in Smart Cities
Sensors 2015, 15(6), 13591-13626; doi:10.3390/s150613591
Received: 9 April 2015 / Revised: 4 June 2015 / Accepted: 8 June 2015 / Published: 10 June 2015
Cited by 5 | PDF Full-text (4627 KB) | HTML Full-text | XML Full-text
Abstract
Information Technology and Communications (ICT) is presented as the main element in order to achieve more efficient and sustainable city resource management, while making sure that the needs of the citizens to improve their quality of life are satisfied. A key element will
[...] Read more.
Information Technology and Communications (ICT) is presented as the main element in order to achieve more efficient and sustainable city resource management, while making sure that the needs of the citizens to improve their quality of life are satisfied. A key element will be the creation of new systems that allow the acquisition of context information, automatically and transparently, in order to provide it to decision support systems. In this paper, we present a novel distributed system for obtaining, representing and providing the flow and movement of people in densely populated geographical areas. In order to accomplish these tasks, we propose the design of a smart sensor network based on RFID communication technologies, reliability patterns and integration techniques. Contrary to other proposals, this system represents a comprehensive solution that permits the acquisition of user information in a transparent and reliable way in a non-controlled and heterogeneous environment. This knowledge will be useful in moving towards the design of smart cities in which decision support on transport strategies, business evaluation or initiatives in the tourism sector will be supported by real relevant information. As a final result, a case study will be presented which will allow the validation of the proposal. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Design and Development of nEMoS, an All-in-One, Low-Cost, Web-Connected and 3D-Printed Device for Environmental Analysis
Sensors 2015, 15(6), 13012-13027; doi:10.3390/s150613012
Received: 23 April 2015 / Revised: 29 May 2015 / Accepted: 29 May 2015 / Published: 4 June 2015
Cited by 4 | PDF Full-text (1561 KB) | HTML Full-text | XML Full-text
Abstract
The Indoor Environmental Quality (IEQ) refers to the quality of the environment in relation to the health and well-being of the occupants. It is a holistic concept, which considers several categories, each related to a specific environmental parameter. This article describes a low-cost
[...] Read more.
The Indoor Environmental Quality (IEQ) refers to the quality of the environment in relation to the health and well-being of the occupants. It is a holistic concept, which considers several categories, each related to a specific environmental parameter. This article describes a low-cost and open-source hardware architecture able to detect the indoor variables necessary for the IEQ calculation as an alternative to the traditional hardware used for this purpose. The system consists of some sensors and an Arduino board. One of the key strengths of Arduino is the possibility it affords of loading the script into the board’s memory and letting it run without interfacing with computers, thus granting complete independence, portability and accuracy. Recent works have demonstrated that the cost of scientific equipment can be reduced by applying open-source principles to their design using a combination of the Arduino platform and a 3D printer. The evolution of the 3D printer has provided a new means of open design capable of accelerating self-directed development. The proposed nano Environmental Monitoring System (nEMoS) instrument is shown to have good reliability and it provides the foundation for a more critical approach to the use of professional sensors as well as for conceiving new scenarios and potential applications. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Low-Cost Sensing System for Cooperative Air Quality Monitoring in Urban Areas
Sensors 2015, 15(6), 12242-12259; doi:10.3390/s150612242
Received: 1 April 2015 / Revised: 8 May 2015 / Accepted: 21 May 2015 / Published: 26 May 2015
Cited by 3 | PDF Full-text (1282 KB) | HTML Full-text | XML Full-text
Abstract
Air quality in urban areas is a very important topic as it closely affects the health of citizens. Recent studies highlight that the exposure to polluted air can increase the incidence of diseases and deteriorate the quality of life. Hence, it is necessary
[...] Read more.
Air quality in urban areas is a very important topic as it closely affects the health of citizens. Recent studies highlight that the exposure to polluted air can increase the incidence of diseases and deteriorate the quality of life. Hence, it is necessary to develop tools for real-time air quality monitoring, so as to allow appropriate and timely decisions. In this paper, we present uSense, a low-cost cooperative monitoring tool that allows knowing, in real-time, the concentrations of polluting gases in various areas of the city. Specifically, users monitor the areas of their interest by deploying low-cost and low-power sensor nodes. In addition, they can share the collected data following a social networking approach. uSense has been tested through an in-field experimentation performed in different areas of a city. The obtained results are in line with those provided by the local environmental control authority and show that uSense can be profitably used for air quality monitoring. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Branch-Based Centralized Data Collection for Smart Grids Using Wireless Sensor Networks
Sensors 2015, 15(5), 11854-11872; doi:10.3390/s150511854
Received: 24 February 2015 / Revised: 14 May 2015 / Accepted: 18 May 2015 / Published: 21 May 2015
PDF Full-text (1168 KB) | HTML Full-text | XML Full-text
Abstract
A smart grid is one of the most important applications in smart cities. In a smart grid, a smart meter acts as a sensor node in a sensor network, and a central device collects power usage from every smart meter. This paper focuses
[...] Read more.
A smart grid is one of the most important applications in smart cities. In a smart grid, a smart meter acts as a sensor node in a sensor network, and a central device collects power usage from every smart meter. This paper focuses on a centralized data collection problem of how to collect every power usage from every meter without collisions in an environment in which the time synchronization among smart meters is not guaranteed. To solve the problem, we divide a tree that a sensor network constructs into several branches. A conflict-free query schedule is generated based on the branches. Each power usage is collected according to the schedule. The proposed method has important features: shortening query processing time and avoiding collisions between a query and query responses. We evaluate this method using the ns-2 simulator. The experimental results show that this method can achieve both collision avoidance and fast query processing at the same time. The success rate of data collection at a sink node executing this method is 100%. Its running time is about 35 percent faster than that of the round-robin method, and its memory size is reduced to about 10% of that of the depth-first search method. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle User Activity Recognition in Smart Homes Using Pattern Clustering Applied to Temporal ANN Algorithm
Sensors 2015, 15(5), 11953-11971; doi:10.3390/s150511953
Received: 11 February 2015 / Accepted: 14 May 2015 / Published: 21 May 2015
Cited by 6 | PDF Full-text (1212 KB) | HTML Full-text | XML Full-text
Abstract
This paper discusses the possibility of recognizing and predicting user activities in the IoT (Internet of Things) based smart environment. The activity recognition is usually done through two steps: activity pattern clustering and activity type decision. Although many related works have been suggested,
[...] Read more.
This paper discusses the possibility of recognizing and predicting user activities in the IoT (Internet of Things) based smart environment. The activity recognition is usually done through two steps: activity pattern clustering and activity type decision. Although many related works have been suggested, they had some limited performance because they focused only on one part between the two steps. This paper tries to find the best combination of a pattern clustering method and an activity decision algorithm among various existing works. For the first step, in order to classify so varied and complex user activities, we use a relevant and efficient unsupervised learning method called the K-pattern clustering algorithm. In the second step, the training of smart environment for recognizing and predicting user activities inside his/her personal space is done by utilizing the artificial neural network based on the Allen’s temporal relations. The experimental results show that our combined method provides the higher recognition accuracy for various activities, as compared with other data mining classification algorithms. Furthermore, it is more appropriate for a dynamic environment like an IoT based smart home. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Evaluation of Three State-of-the-Art Classifiers for Recognition of Activities of Daily Living from Smart Home Ambient Data
Sensors 2015, 15(5), 11725-11740; doi:10.3390/s150511725
Received: 10 March 2015 / Revised: 13 May 2015 / Accepted: 14 May 2015 / Published: 21 May 2015
Cited by 3 | PDF Full-text (1286 KB) | HTML Full-text | XML Full-text
Abstract
Smart homes for the aging population have recently started attracting the attention of the research community. The “health state” of smart homes is comprised of many different levels; starting with the physical health of citizens, it also includes longer-term health norms and outcomes,
[...] Read more.
Smart homes for the aging population have recently started attracting the attention of the research community. The “health state” of smart homes is comprised of many different levels; starting with the physical health of citizens, it also includes longer-term health norms and outcomes, as well as the arena of positive behavior changes. One of the problems of interest is to monitor the activities of daily living (ADL) of the elderly, aiming at their protection and well-being. For this purpose, we installed passive infrared (PIR) sensors to detect motion in a specific area inside a smart apartment and used them to collect a set of ADL. In a novel approach, we describe a technology that allows the ground truth collected in one smart home to train activity recognition systems for other smart homes. We asked the users to label all instances of all ADL only once and subsequently applied data mining techniques to cluster in-home sensor firings. Each cluster would therefore represent the instances of the same activity. Once the clusters were associated to their corresponding activities, our system was able to recognize future activities. To improve the activity recognition accuracy, our system preprocessed raw sensor data by identifying overlapping activities. To evaluate the recognition performance from a 200-day dataset, we implemented three different active learning classification algorithms and compared their performance: naive Bayesian (NB), support vector machine (SVM) and random forest (RF). Based on our results, the RF classifier recognized activities with an average specificity of 96.53%, a sensitivity of 68.49%, a precision of 74.41% and an F-measure of 71.33%, outperforming both the NB and SVM classifiers. Further clustering markedly improved the results of the RF classifier. An activity recognition system based on PIR sensors in conjunction with a clustering classification approach was able to detect ADL from datasets collected from different homes. Thus, our PIR-based smart home technology could improve care and provide valuable information to better understand the functioning of our societies, as well as to inform both individual and collective action in a smart city scenario. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Multi-User Game-Theoretical Multipath Routing Protocol to Send Video-Warning Messages over Mobile Ad Hoc Networks
Sensors 2015, 15(4), 9039-9077; doi:10.3390/s150409039
Received: 19 February 2015 / Revised: 6 April 2015 / Accepted: 14 April 2015 / Published: 17 April 2015
PDF Full-text (1678 KB) | HTML Full-text | XML Full-text
Abstract
The prevention of accidents is one of the most important goals of ad hoc networks in smart cities. When an accident happens, dynamic sensors (e.g., citizens with smart phones or tablets, smart vehicles and buses, etc.) could shoot a video clip of the
[...] Read more.
The prevention of accidents is one of the most important goals of ad hoc networks in smart cities. When an accident happens, dynamic sensors (e.g., citizens with smart phones or tablets, smart vehicles and buses, etc.) could shoot a video clip of the accident and send it through the ad hoc network. With a video message, the level of seriousness of the accident could be much better evaluated by the authorities (e.g., health care units, police and ambulance drivers) rather than with just a simple text message. Besides, other citizens would be rapidly aware of the incident. In this way, smart dynamic sensors could participate in reporting a situation in the city using the ad hoc network so it would be possible to have a quick reaction warning citizens and emergency units. The deployment of an efficient routing protocol to manage video-warning messages in mobile Ad hoc Networks (MANETs) has important benefits by allowing a fast warning of the incident, which potentially can save lives. To contribute with this goal, we propose a multipath routing protocol to provide video-warning messages in MANETs using a novel game-theoretical approach. As a base for our work, we start from our previous work, where a 2-players game-theoretical routing protocol was proposed to provide video-streaming services over MANETs. In this article, we further generalize the analysis made for a general number of N players in the MANET. Simulations have been carried out to show the benefits of our proposal, taking into account the mobility of the nodes and the presence of interfering traffic. Finally, we also have tested our approach in a vehicular ad hoc network as an incipient start point to develop a novel proposal specifically designed for VANETs. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Nonlinear Optimization-Based Device-Free Localization with Outlier Link Rejection
Sensors 2015, 15(4), 8072-8087; doi:10.3390/s150408072
Received: 5 February 2015 / Revised: 18 March 2015 / Accepted: 25 March 2015 / Published: 7 April 2015
Cited by 5 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
Device-free localization (DFL) is an emerging wireless technique for estimating the location of target that does not have any attached electronic device. It has found extensive use in Smart City applications such as healthcare at home and hospitals, location-based services at smart spaces,
[...] Read more.
Device-free localization (DFL) is an emerging wireless technique for estimating the location of target that does not have any attached electronic device. It has found extensive use in Smart City applications such as healthcare at home and hospitals, location-based services at smart spaces, city emergency response and infrastructure security. In DFL, wireless devices are used as sensors that can sense the target by transmitting and receiving wireless signals collaboratively. Many DFL systems are implemented based on received signal strength (RSS) measurements and the location of the target is estimated by detecting the changes of the RSS measurements of the wireless links. Due to the uncertainty of the wireless channel, certain links may be seriously polluted and result in erroneous detection. In this paper, we propose a novel nonlinear optimization approach with outlier link rejection (NOOLR) for RSS-based DFL. It consists of three key strategies, including: (1) affected link identification by differential RSS detection; (2) outlier link rejection via geometrical positional relationship among links; (3) target location estimation by formulating and solving a nonlinear optimization problem. Experimental results demonstrate that NOOLR is robust to the fluctuation of the wireless signals with superior localization accuracy compared with the existing Radio Tomographic Imaging (RTI) approach. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Design of a Hybrid (Wired/Wireless) Acquisition Data System for Monitoring of Cultural Heritage Physical Parameters in Smart Cities
Sensors 2015, 15(4), 7246-7266; doi:10.3390/s150407246
Received: 8 January 2015 / Revised: 4 March 2015 / Accepted: 16 March 2015 / Published: 25 March 2015
Cited by 2 | PDF Full-text (4608 KB) | HTML Full-text | XML Full-text
Abstract
Preventive conservation represents a working method and combination of techniques which helps in determining and controlling the deterioration process of cultural heritage in order to take the necessary actions before it occurs. It is acknowledged as important, both in terms of preserving and
[...] Read more.
Preventive conservation represents a working method and combination of techniques which helps in determining and controlling the deterioration process of cultural heritage in order to take the necessary actions before it occurs. It is acknowledged as important, both in terms of preserving and also reducing the cost of future conservation measures. Therefore, long-term monitoring of physical parameters influencing cultural heritage is necessary. In the context of Smart Cities, monitoring of cultural heritage is of interest in order to perform future comparative studies and load information into the cloud that will be useful for the conservation of other heritage sites. In this paper the development of an economical and appropriate acquisition data system combining wired and wireless communication, as well as third party hardware for increased versatility, is presented. The device allows monitoring a complex network of points with high sampling frequency, with wired sensors in a 1-wire bus and a wireless centralized system recording data for monitoring of physical parameters, as well as the future possibility of attaching an alarm system or sending data over the Internet. This has been possible with the development of three board’s designs and more than 5000 algorithm lines. System tests have shown an adequate system operation. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Opportunistic Mobility Support for Resource Constrained Sensor Devices in Smart Cities
Sensors 2015, 15(3), 5112-5135; doi:10.3390/s150305112
Received: 23 December 2014 / Revised: 11 February 2015 / Accepted: 13 February 2015 / Published: 2 March 2015
Cited by 1 | PDF Full-text (2087 KB) | HTML Full-text | XML Full-text
Abstract
A multitude of wireless sensor devices and technologies are being developed and deployed in cities all over the world. Sensor applications in city environments may include highly mobile installations that span large areas which necessitates sensor mobility support. This paper presents and validates
[...] Read more.
A multitude of wireless sensor devices and technologies are being developed and deployed in cities all over the world. Sensor applications in city environments may include highly mobile installations that span large areas which necessitates sensor mobility support. This paper presents and validates two mechanisms for supporting sensor mobility between different administrative domains. Firstly, EAP-Swift, an Extensible Authentication Protocol (EAP)-based sensor authentication protocol is proposed that enables light-weight sensor authentication and key generation. Secondly, a mechanism for handoffs between wireless sensor gateways is proposed. We validate both mechanisms in a real-life study that was conducted in a smart city environment with several fixed sensors and moving gateways. We conduct similar experiments in an industry-based anechoic Long Term Evolution (LTE) chamber with an ideal radio environment. Further, we validate our results collected from the smart city environment against the results produced under ideal conditions to establish best and real-life case scenarios. Our results clearly validate that our proposed mechanisms can facilitate efficient sensor authentication and handoffs while sensors are roaming in a smart city environment. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Multi-Stage Method for Connecting Participatory Sensing and Noise Simulations
Sensors 2015, 15(2), 2265-2282; doi:10.3390/s150202265
Received: 30 September 2014 / Revised: 7 January 2015 / Accepted: 9 January 2015 / Published: 22 January 2015
Cited by 1 | PDF Full-text (22883 KB) | HTML Full-text | XML Full-text
Abstract
Most simulation-based noise maps are important for official noise assessment but lack local noise characteristics. The main reasons for this lack of information are that official noise simulations only provide information about expected noise levels, which is limited by the use of large-scale
[...] Read more.
Most simulation-based noise maps are important for official noise assessment but lack local noise characteristics. The main reasons for this lack of information are that official noise simulations only provide information about expected noise levels, which is limited by the use of large-scale monitoring of noise sources, and are updated infrequently. With the emergence of smart cities and ubiquitous sensing, the possible improvements enabled by sensing technologies provide the possibility to resolve this problem. This study proposed an integrated methodology to propel participatory sensing from its current random and distributed sampling origins to professional noise simulation. The aims of this study were to effectively organize the participatory noise data, to dynamically refine the granularity of the noise features on road segments (e.g., different portions of a road segment), and then to provide a reasonable spatio-temporal data foundation to support noise simulations, which can be of help to researchers in understanding how participatory sensing can play a role in smart cities. This study first discusses the potential limitations of the current participatory sensing and simulation-based official noise maps. Next, we explain how participatory noise data can contribute to a simulation-based noise map by providing (1) spatial matching of the participatory noise data to the virtual partitions at a more microscopic level of road networks; (2) multi-temporal scale noise estimations at the spatial level of virtual partitions; and (3) dynamic aggregation of virtual partitions by comparing the noise values at the relevant temporal scale to form a dynamic segmentation of each road segment to support multiple spatio-temporal noise simulations. In this case study, we demonstrate how this method could play a significant role in a simulation-based noise map. Together, these results demonstrate the potential benefits of participatory noise data as dynamic input sources for noise simulations on multiple spatio-temporal scales. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Integrated Semantics Service Platform for the Internet of Things: A Case Study of a Smart Office
Sensors 2015, 15(1), 2137-2160; doi:10.3390/s150102137
Received: 11 October 2014 / Revised: 17 November 2014 / Accepted: 12 January 2015 / Published: 19 January 2015
Cited by 9 | PDF Full-text (2258 KB) | HTML Full-text | XML Full-text
Abstract
The Internet of Things (IoT) allows machines and devices in the world to connect with each other and generate a huge amount of data, which has a great potential to provide useful knowledge across service domains. Combining the context of IoT with semantic
[...] Read more.
The Internet of Things (IoT) allows machines and devices in the world to connect with each other and generate a huge amount of data, which has a great potential to provide useful knowledge across service domains. Combining the context of IoT with semantic technologies, we can build integrated semantic systems to support semantic interoperability. In this paper, we propose an integrated semantic service platform (ISSP) to support ontological models in various IoT-based service domains of a smart city. In particular, we address three main problems for providing integrated semantic services together with IoT systems: semantic discovery, dynamic semantic representation, and semantic data repository for IoT resources. To show the feasibility of the ISSP, we develop a prototype service for a smart office using the ISSP, which can provide a preset, personalized office environment by interpreting user text input via a smartphone. We also discuss a scenario to show how the ISSP-based method would help build a smart city, where services in each service domain can discover and exploit IoT resources that are wanted across domains. We expect that our method could eventually contribute to providing people in a smart city with more integrated, comprehensive services based on semantic interoperability. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Proxy Design to Leverage the Interconnection of CoAP Wireless Sensor Networks with Web Applications
Sensors 2015, 15(1), 1217-1244; doi:10.3390/s150101217
Received: 17 November 2014 / Accepted: 23 December 2014 / Published: 9 January 2015
Cited by 5 | PDF Full-text (1706 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present the design of a Constrained Application Protocol (CoAP) proxy able to interconnect Web applications based on Hypertext Transfer Protocol (HTTP) and WebSocket with CoAP based Wireless Sensor Networks. Sensor networks are commonly used to monitor and control physical
[...] Read more.
In this paper, we present the design of a Constrained Application Protocol (CoAP) proxy able to interconnect Web applications based on Hypertext Transfer Protocol (HTTP) and WebSocket with CoAP based Wireless Sensor Networks. Sensor networks are commonly used to monitor and control physical objects or environments. Smart Cities represent applications of such a nature. Wireless Sensor Networks gather data from their surroundings and send them to a remote application. This data flow may be short or long lived. The traditional HTTP long-polling used by Web applications may not be adequate in long-term communications. To overcome this problem, we include the WebSocket protocol in the design of the CoAP proxy. We evaluate the performance of the CoAP proxy in terms of latency and memory consumption. The tests consider long and short-lived communications. In both cases, we evaluate the performance obtained by the CoAP proxy according to the use of WebSocket and HTTP long-polling. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Smart City Application: A Fully Controlled Street Lighting Isle Based on Raspberry-Pi Card, a ZigBee Sensor Network and WiMAX
Sensors 2014, 14(12), 24408-24424; doi:10.3390/s141224408
Received: 27 October 2014 / Revised: 5 December 2014 / Accepted: 12 December 2014 / Published: 18 December 2014
Cited by 22 | PDF Full-text (1454 KB) | HTML Full-text | XML Full-text
Abstract
A smart city application has been realized and tested. It is a fully remote controlled isle of lamp posts based on new technologies. It has been designed and organized in different hierarchical layers, which perform local activities to physically control the lamp posts
[...] Read more.
A smart city application has been realized and tested. It is a fully remote controlled isle of lamp posts based on new technologies. It has been designed and organized in different hierarchical layers, which perform local activities to physically control the lamp posts and transmit information with another for remote control. Locally, each lamp post uses an electronic card for management and a ZigBee tlc network transmits data to a central control unit, which manages the whole isle. The central unit is realized with a Raspberry-Pi control card due to its good computing performance at very low price. Finally, a WiMAX connection was tested and used to remotely control the smart grid, thus overcoming the distance limitations of commercial Wi-Fi networks. The isle has been realized and tested for some months in the field. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle Definition of an Ontology Matching Algorithm for Context Integration in Smart Cities
Sensors 2014, 14(12), 23581-23619; doi:10.3390/s141223581
Received: 9 October 2014 / Revised: 3 November 2014 / Accepted: 5 November 2014 / Published: 8 December 2014
Cited by 2 | PDF Full-text (458 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we describe a novel proposal in the field of smart cities: using an ontology matching algorithm to guarantee the automatic information exchange between the agents and the smart city. A smart city is composed by different types of agents that
[...] Read more.
In this paper we describe a novel proposal in the field of smart cities: using an ontology matching algorithm to guarantee the automatic information exchange between the agents and the smart city. A smart city is composed by different types of agents that behave as producers and/or consumers of the information in the smart city. In our proposal, the data from the context is obtained by sensor and device agents while users interact with the smart city by means of user or system agents. The knowledge of each agent, as well as the smart city’s knowledge, is semantically represented using different ontologies. To have an open city, that is fully accessible to any agent and therefore to provide enhanced services to the users, there is the need to ensure a seamless communication between agents and the city, regardless of their inner knowledge representations, i.e., ontologies. To meet this goal we use ontology matching techniques, specifically we have defined a new ontology matching algorithm called OntoPhil to be deployed within a smart city, which has never been done before. OntoPhil was tested on the benchmarks provided by the well known evaluation initiative, Ontology Alignment Evaluation Initiative, and also compared to other matching algorithms, although these algorithms were not specifically designed for smart cities. Additionally, specific tests involving a smart city’s ontology and different types of agents were conducted to validate the usefulness of OntoPhil in the smart city environment. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Cloud-Based Car Parking Middleware for IoT-Based Smart Cities: Design and Implementation
Sensors 2014, 14(12), 22372-22393; doi:10.3390/s141222372
Received: 3 October 2014 / Revised: 12 November 2014 / Accepted: 19 November 2014 / Published: 25 November 2014
Cited by 7 | PDF Full-text (3410 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the generic concept of using cloud-based intelligent car parking services in smart cities as an important application of the Internet of Things (IoT) paradigm. This type of services will become an integral part of a generic IoT operational platform for
[...] Read more.
This paper presents the generic concept of using cloud-based intelligent car parking services in smart cities as an important application of the Internet of Things (IoT) paradigm. This type of services will become an integral part of a generic IoT operational platform for smart cities due to its pure business-oriented features. A high-level view of the proposed middleware is outlined and the corresponding operational platform is illustrated. To demonstrate the provision of car parking services, based on the proposed middleware, a cloud-based intelligent car parking system for use within a university campus is described along with details of its design, implementation, and operation. A number of software solutions, including Kafka/Storm/Hbase clusters, OSGi web applications with distributed NoSQL, a rule engine, and mobile applications, are proposed to provide ‘best’ car parking service experience to mobile users, following the Always Best Connected and best Served (ABC&S) paradigm. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)
Open AccessArticle A Multi-Modal Face Recognition Method Using Complete Local Derivative Patterns and Depth Maps
Sensors 2014, 14(10), 19561-19581; doi:10.3390/s141019561
Received: 8 August 2014 / Revised: 3 October 2014 / Accepted: 13 October 2014 / Published: 20 October 2014
Cited by 1 | PDF Full-text (1439 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we propose a multi-modal 2D + 3D face recognition method for a smart city application based on a Wireless Sensor Network (WSN) and various kinds of sensors. Depth maps are exploited for the 3D face representation. As for feature extraction,
[...] Read more.
In this paper, we propose a multi-modal 2D + 3D face recognition method for a smart city application based on a Wireless Sensor Network (WSN) and various kinds of sensors. Depth maps are exploited for the 3D face representation. As for feature extraction, we propose a new feature called Complete Local Derivative Pattern (CLDP). It adopts the idea of layering and has four layers. In the whole system, we apply CLDP separately on Gabor features extracted from a 2D image and depth map. Then, we obtain two features: CLDP-Gabor and CLDP-Depth. The two features weighted by the corresponding coefficients are combined together in the decision level to compute the total classification distance. At last, the probe face is assigned the identity with the smallest classification distance. Extensive experiments are conducted on three different databases. The results demonstrate the robustness and superiority of the new approach. The experimental results also prove that the proposed multi-modal 2D + 3D method is superior to other multi-modal ones and CLDP performs better than other Local Binary Pattern (LBP) based features. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)

Review

Jump to: Research

Open AccessReview Using a Smart City IoT to Incentivise and Target Shifts in Mobility Behaviour—Is It a Piece of Pie?
Sensors 2015, 15(6), 13069-13096; doi:10.3390/s150613069
Received: 1 May 2015 / Revised: 18 May 2015 / Accepted: 22 May 2015 / Published: 4 June 2015
Cited by 9 | PDF Full-text (933 KB) | HTML Full-text | XML Full-text
Abstract
Whilst there is an increasing capability to instrument smart cities using fixed and mobile sensors to produce the big data to better understand and manage transportation use, there still exists a wide gap between the sustainability goals of smart cities, e.g., to promote
[...] Read more.
Whilst there is an increasing capability to instrument smart cities using fixed and mobile sensors to produce the big data to better understand and manage transportation use, there still exists a wide gap between the sustainability goals of smart cities, e.g., to promote less private car use at peak times, with respect to their ability to more dynamically support individualised shifts in multi-modal transportation use to help achieve such goals. We describe the development of the tripzoom system developed as part of the SUNSET—SUstainable social Network SErvices for Transport—project to research and develop a mobile and fixed traffic sensor system to help facilitate individual mobility shifts. Its main novelty was its ability to use mobile sensors to classify common multiple urban transportation modes, to generate information-rich individual and group mobility profiles and to couple this with the use of a targeted incentivised marketplace to gamify travel. This helps to promote mobility shifts towards achieving sustainability goals. This system was trialled in three European country cities operated as Living Labs over six months. Our main findings were that we were able to accomplish a level of behavioural shifts in travel behaviour. Hence, we have provided a proof-of-concept system that uses positive incentives to change individual travel behaviour. Full article
(This article belongs to the Special Issue Sensors and Smart Cities)

Journal Contact

MDPI AG
Sensors Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
sensors@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Sensors
Back to Top