Publications

Enhanced Still Presence Sensing with Supervised Learning over Segmented Ultrasonic Reflections, Abbass Hammoud, Athanasios I. Kyritsis, Michel Deriaz and Dimitri Konstantas, in The Eighth International Conference on Indoor Positioning and Indoor Navigation (IPIN 2017), Sapporo, Japan, 2017.

Abstract. Sensing the presence of people in indoor spaces allows smart systems to be aware of and responsive to the occupants, and paves the way for a wide range of applications. In this paper, we show how the reflection patterns of ultrasonic signals can be leveraged to detect the presence of still persons. We propose the use of supervised learning over segmented reflection patterns, and prove that this method is capable of detecting minute variations in the environment's response. The experimental evaluation of the proposed method in an office and a residential environment shows that it achieves a high presence sensing accuracy in the case of low signal-to-noise ratio (SNR), and a perfect accuracy in the case of high SNR, even in the case of non line-of-sight. Among the different tested classifiers, we found that the linear Support Vector Machine (SVM) achieves the best performance, yielding a presence detection accuracy of 84.3%-98.4% for low SNR, and 100% for high SNR, in the tested environments.

A Multiobjective Optimization Methodology of Tuning Indoor Positioning Systems, Grigorios G. Anagnostopoulos, Michel Deriaz and Dimitri Konstantas, in The Eighth International Conference on Indoor Positioning and Indoor Navigation (IPIN 2017), Sapporo, Japan, 2017.

Abstract. How can the collected data from testing an indoor positioning deployment be transformed into information concerning the optimal tuning of a positioning system in this deployment? How can such kind of accumulated information from several deployments be transformed into more generic knowledge regarding the system’s performance, with respect to several performance goals? In this work, we present a multiobjective optimization methodology of tuning indoor positioning systems, based on real data recorded onsite. Selecting the appropriate tuning for a positioning system is a challenging task, which depends on many factors: the specific deployment, the devices used, the evaluation metrics and their order of significance, the user-case scenarios tested, etc. In order to handle these multiplicities, we introduce the use of multiobjective optimization which allows several objectives to be simultaneously satisfied. We exemplify the methodology performing tests with the GpmStudio platform, a desktop tuning and evaluation platform that supports our Global Positioning Module (GPM). The methodology proves to be a very useful tool in the hands of testers who are designated to optimally tune the positioning system in a variety of scenarios.

Navigational needs and requirements of hospital staff: Geneva University Hospitals case study, Grigorios G. Anagnostopoulos, Michel Deriaz, Jean-Michel Gaspoz, Dimitri Konstantas and Idris Guessous, in The Eighth International Conference on Indoor Positioning and Indoor Navigation (IPIN 2017), Sapporo, Japan, 2017.

Abstract. Navigating in large hospitals is a challenging task. The consequences of difficulties faced by staff, patients and visitors in finding their way in the hospital can be multiple. The HUGApp project goals are to identify the navigational needs and requirements of people within the premises of Geneva University Hospitals (HUG) before proceeding with potential solutions, such as an indoor navigation mobile app. A questionnaire was designed and distributed to staff members with the goal of understanding the current problems in wayfinding inside HUG, investigating the users’ views on the creation of an indoor navigation mobile app, and specifying the user requirements for such an app. A total of 111 members of the primary care division of HUG answered the questionnaire, providing an insightful view of the healthcare professionals.

Power Hopping: an Automatic Power Optimization Method for Ultrasonic Motion Sensors, Abbass Hammoud, Grigorios G. Anagnostopoulos, Athanasios I. Kyritsis, Michel Deriaz, Dimitri Konstantas, in The Fourteenth International Conference on Ubiquitous Intelligence and Computing (UIC-2017), San Francisco, USA, 2017.

Abstract. Ultrasonic motion sensors are used to obtain occupancy information of indoor spaces. Although they provide a high accuracy as compared to other sensors, like Passive InfraRed (PIR), they require a higher power consumption in general. In this paper we propose power hopping, an automatic power optimization method that allows ultrasound motion sensors to optimize their transmitter power level. The objective is to reduce the overall energy consumption of these sensors. We have tested our method using a sensor prototype, and the results show that, depending on the sensor's environment, a possible saving in the transmitter power can be achieved, which can be as high as 78%. We also derive an upper bound limit of the method's convergence time.

UltraSense: a Self-Calibrating Ultrasound-Based Room Occupancy Sensing System, Abbass Hammoud, Michel Deriaz, Dimitri Konstantas, in The Eighth International Conference on Ambient Systems, Networks and Technologies (ANT-2017), Madeira, Portugal​, 2017.

Abstract. Smart sensing technologies play a key role in the core of smart systems, which form the rapidly evolving internet of things. In this context, buildings' occupancy information is an important input that allows smart systems to be seamlessly aware of and responsive to the inhabitants, thus ensuring their comfort. In this paper we present UltraSense, an ultrasound-based room occupancy sensing system that relies on unsupervised learning, to automatically calibrate its parameters according to the room's environment. This ability avoids the need for manual calibration of the sensing system for each new environment. While commonly available occupancy detection technologies are limited to line-of-sight (LOS) conditions, UltraSense also operates in non line-of-sight (NLOS) scenarios. The proposed system was implemented and tested in order to characterize its performance. UltraSense was developed for the European research project SmartHeat in the frame of ambient assisted living.

“Getting lost” in hospital is a source of stress among staff members, Grigorios Anagnostopoulos, Michel Deriaz, Jean-Michel Gaspoz, Dimitri Konstantas, Idris Guessous, in The 2017 SGIM Annual Meeting: Resilience & Grit - Pursuing Organizational Change & Preventing Burnout in GIM​, Washington DC​, USA, 2017.

Abstract. Navigating around large hospitals has been shown to be a stressful and time-consuming experience for all users of the hospital, including staff members. In addition, navigation difficulties in a hospital highlight suboptimal organisation. When staff encounters navigation difficulties this can lead to cost and efficiency issues and potentially put patient safety at risk. Despite the provision of an array of in-hospital navigational aids, ‘getting lost’ continues to be an everyday problem in these large complex environments. Within the framework of developing a navigation mobile app for the largest university hospital of Switzerland (Geneva University Hospitals), we aimed to identify the navigational needs of, problems encountered by, and consequences to primary care staff. A questionnaire was developed by a primary care physician and an indoor navigation specialist (both from Geneva’s University) based on factors identified through a review of the literature. The questionnaire was constructed to reflect all professional activities encountered in the primary care division and was sent in 2016 to both physicians and non-physician healthcare providers. The questionnaire includes the identification of current problems in way finding inside the hospital (stationary and ambulatory) and their impacts on the staff’s work. These results show that even for staff members of a large hospital, finding their destination is difficult, consumes time, and might be a source of stress. Improving wayfinding could contribute to pursuing organizational change, improve efficiency, and decrease stress.

Robust Ultrasound-Based Room-Level Localization System Using COTS Components, Abbass Hammoud, Michel Deriaz and Dimitri Konstantas, in proceedings of The Fourth IEEE International Conference on Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS 2016), Shanghai, China, 2016.

Abstract. Location-based services have become very popular in recent years. Although many previous works targeted the problem of indoor localization, several reasons still prevent the widespread adoption of most systems' implementations. Some of these reasons are their insufficient availability, and the need for extensive node deployment and maintenance. In this work, we present a highly accurate room-level indoor localization system that is based on ultrasound technology. Our system is robust to noise, scalable, has a low complexity on the receiver, and does not require synchronization between transmitter and receiver. Moreover, it uses commercial off-the-shelf (COTS) components and does not require special hardware or additional infrastructure to be deployed. The system relies solely on ultrasound, and does not use any RF signals. To deal with the problem of signal interference, we explain how signal collisions can be detected, and we propose a method for collision avoidance. The system was implemented and tested in scenarios with realistic conditions. The results prove that the proposed system is accurate and robust to ambient noise. This work was conducted in the frame of the European project 'SmartHeat', which aims to improve heating conditions of elderly people, and reduce energy consumption. It employs rooms' occupancy information with other inputs, to adapt the heating according to users' habits.

Practical Evaluation and Tuning Methodology for Indoor Positioning Systems, Grigorios G. Anagnostopoulos, Carlos Martínez de la Osa, Tiago Nunes, Abbass Hammoud, Michel Deriaz and Dimitri Konstantas, in proceedings of The Fourth IEEE International Conference on Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS 2016), Shanghai, China, 2016.

Abstract. How do we evaluate the performance of an indoor positioning system? In addition, in which way can the system be optimally tuned for a certain environment? These are the questions addressed in this study. We propose a practical, cost efficient methodology for evaluating and tuning indoor positioning systems. The methodology has two main phases. In the first online recording phase, the ground truth information is gathered, and raw signals are recorded. In the second phase, offline positioning algorithms utilise the recorded information to infer position estimations which can then be precisely evaluated. An automatic parameter optimization methodology, which recommends optimal tunings for the positioning algorithm, is presented as a key utility of this work. An overall advantage of the proposed method is the fact that the recorded data guarantee the repeatability of tests, and allow consistent comparisons among different algorithms, creating the perspective of a testbed based on real data. The implementation of the methodology is exemplified with the presentation of the GpmLab Android application and the GpmStudio desktop platform, tools which assist our main positioning framework, the Global Positioning Module (GPM).

Online Self-Calibration of the Propagation Model for Indoor Positioning Ranging Methods, Grigorios G. Anagnostopoulos, Michel Deriaz and Dimitri Konstantas, in proceedings of The Seventh International Conference On Indoor Positioning and Indoor Navigation (IPIN 2016), Madrid, Spain, October 2016.

Abstract. A common problem for indoor positioning methods is the fact that the differences in the reception characteristics among devices may significantly deteriorate the performance of a positioning system. Ranging algorithms for positioning rely on the accuracy of the parameters of the propagation model. This model is used to infer an estimate of the distance of a mobile device from each access point from the Received Signal Strength Indication (RSSI). In this work we present an algorithm which dynamically recalculates and improves the propagation model. The improvement of the model parameters fits the environment’s characteristics and, more importantly, the reception characteristics of the device used. The proposed algorithm is tested with different devices at an indoor deployment covering a large area where Bluetooth Low Energy (BLE) technology is used. The experimental results show that the proposed method offers a significant accuracy improvement to some devices while it slightly improves the performance of those that are more properly tuned.

Positioning Evaluation and Ground Truth Definition for Real Life Use Cases, Carlos Martínez de la Osa, Grigorios G. Anagnostopoulos, Mauricio Togneri, Michel Deriaz and Dimitri Konstantas, in proceedings of The Seventh International Conference On Indoor Positioning and Indoor Navigation (IPIN 2016), Madrid, Spain, October 2016.

Abstract. Evaluating positioning systems has become a matter of heated debate during the last years. There is no clear standard on how these technologies should be evaluated, and no predominant solution for defining the ground truth in order to compare the position estimates. In this paper, we propose a simple and inexpensive solution for tackling both of these problems in real life use cases. With the proposed methodology, it is possible to measure both static and moving targets, by creating a predefined path with checkpoints. Then, a tester, walking over them, while moving or standing still, indicates when the device was over the aforementioned checkpoints. It is also specified how to evaluate the estimates by comparing them with interpolated points of the ground truth trajectory. Two methods are proposed for performing such interpolation. Finally, in order to evaluate the performance of the positioning system as well as the perceived utility of the position estimates from the end user’s point of view, a series of statistical parameters is discussed. Additionally, in the context of perceived utility by the end user, a parameter that measures the occurrence of abrupt changes in the position estimates is proposed.

F2D: A location aware fall detection system tested with real data from daily life of elderly people, Panagiotis Kostopoulos, Athanasios I. Kyritsis, Michel Deriaz and Dimitri Konstantas, in proceedings of The Sixth International Conference on Current and Future Trends of Information and Communication Technologies in Healthcare (ICTH 2016), London, United Kingdom, September 2016.

Abstract. Falls among older people remain a very important public healthcare issue. In the majority of fall events external support is imperative in order to avoid major consequences. Therefore, the ability to automatically detect these fall events could help reducing the response time and significantly improve the prognosis of fall victims. This paper presents a practical real time fall detection system running on a smartwatch (F2D). A decision module takes into account the rebound after the fall and the residual movement of the user, matching a detected fall pattern to an actual fall. The last module of F2D is the location module which makes our system very useful for nursing homes that host elderly people. The fall detection algorithm has been tested by Fondation Suisse pour les Téléthèses (FST), the project partner who is responsible for the commercialization of our system. By testing with real data and achieving an accuracy of 96.01% we have a fall detection system ready to be deployed on the market and by adding the location module we can provide it to nursing homes for elderly people.

A BLE-Based Probabilistic Room-Level Localization Method, Athanasios I. Kyritsis, Panagiotis Kostopoulos, Michel Deriaz and Dimitri Konstantas, in proceedings of The Sixth International Conference On Localization and GNSS (ICL-GNSS 2016), Barcelona, Spain, June 2016.

Abstract. During the last decades, location based services have become very popular and the developed indoor positioning systems have achieved an impressive accuracy. The problem though is that even if the only requirement is room-level localization, those systems are most of the times not cost-efficient and not easy to set-up, since they often require time-consuming calibration procedures. This paper presents a low-cost, threshold-based approach and introduces an algorithm that takes into account both the Received Signal Strength Indication (RSSI) of the Bluetooth Low Energy (BLE) beacons and the geometry of the rooms the beacons are placed in. Performance evaluation was done via measurements in an office environment composed of three rooms and in a house environment composed of six rooms. The experimental results show an improved accuracy in room detection when using the proposed algorithm, compared to when only considering the RSSI readings. This method was developed to provide context awareness to the international research project named SmartHeat. The projects aims to provide a system that efficiently heats a house, room by room, based on the habitants’ habits and preferences.

Stress detection using smart phone data, Panagiotis Kostopoulos, Athanasios Kyritsis, Michel Deriaz and Dimitri Konstantas, in proceedings of The EAI International Conference on Wearables in Healthcare (EAI 2016), Budapest, Hungary, June 2016.

Abstract. In today's society, working environments are becoming more stressful. The problem of occupational stress is generally recognized as one of the major factors leading to a wide spectrum of health problems. However work should, ideally, be a source of health, pride and happiness, in the sense of enhancing motivation and strengthening personal development. In this work, we present StayActive, a system which aims to detect stress and burn-out risks by analyzing the behaviour of the users via their smartphone. The main purpose of StayActive is the use of the mobile sensor technology for detecting stress. Then a mobile service can recommend and present various relaxation activities "just in time" in order to allow users to carry out and solve everyday tasks and problems at work. In particular, we collect data from people's daily phone usage gathering information about the sleeping pattern, the social interaction and the physical activity of the user. We assign a weight factor to each of these three dimensions of wellbeing according to the user's personal perception and build a stress detection system. We evaluate our system in a real world environment with young adults and people working in the transportation company of Geneva. This paper highlights the architecture and model of this innovative stress detection system. The main innovation of this work is addressed in the fact that the way the stress level is computed is as less invasive as possible for the users.

StayActive: An Application for Detecting Stress, Panagiotis Kostopoulos, Tiago Nunes, Kevin Salvi, Mauricio Togneri and Michel Deriaz, in proceedings of The Fourth International Conference on Communications, Computation, Networks and Technologies (INNOV 2015), Barcelona, Spain, November 2015.

Abstract. In today’s society, working environments are becoming more stressful and people working in these environments become prone to various illnesses. But, work should be a source of health, pride and happiness, in the sense of enhancing motivation and strengthening personal development. In this work, we present StayActive, a system which aims to detect stress and burnout risks by analyzing the behaviour of the users via their smartphone. In particular, we collect data from people’s daily phone usage gathering information about the sleeping pattern, the social interaction and the physical activity of the user. We assign a weight factor to each of these three dimensions of wellbeing according to the user’s personal perception and build a stress detection system. We evaluate our system in a real world environment and in a daily-routine scenario. This paper highlights the architecture and model of this innovative stress detection system.

Smart Position Selection in Mobile Localisation, Carlos Martinez, Grigorios G. Anagnostopoulos, Michel Deriaz, in proceedings of The Fourth International Conference on Communications, Computation, Networks and Technologies (INNOV 2015), Barcelona, Spain, November 2015.

Abstract. Which technology should be used in order to be able to locate oneself in any kind of scenario? This has been a recurrent question in the last years. It has become evident that, until now, there is no dominant indoor positioning solution based on a single technology. Outdoors, positioning systems based on satellites have given excellent results. However, a global solution for both kinds of scenarios does not exist. In our study, this problem is dealt with by creating an algorithm able to evaluate positions received from different technologies and choose the most trustworthy one. As a result, we are able to improve the overall accuracy of the user’s position estimation, compared to the ones the different technologies would have given if used independently. In this way, the user is offered a simple solution to have an accurate position in all environments, in a transparent way. The main challenge of using different technologies at the same time is usually the battery consumption. A solution for dealing with this aspect is also proposed in this document. This research has been done in the context of the Ambient Assisted Living (AAL) Enhanced Daily Living and Health (EDLAH) project, where older people can track their lost objects, which requires them to be positioned in a very accurate way.

Automatic Switching Between Indoor and Outdoor Position Providers, Grigorios G. Anagnostopoulos, Michel Deriaz, in proceedings of the Sixth International Conference on Indoor Positioning And Indoor Navigation (IPIN 2015), Banff, Alberta, Canada, October 2015.

Abstract. In which way may an application switch instantly and reliably between an indoor and an outdoor positioning provider as a user enters and exits buildings? In this work we present a robust switching algorithm, utilizing the dynamic accuracy estimation of each position provider as a reliability indication. Our algorithm offers a fast automatic switch between the indoor and the outdoor provider, in a transparent way for the user. We also present experimental results, using GPS outdoors and a Bluetooth provider indoors. This technique was tested in our lab and was afterwards installed at the Hospital of Perugia, Italy, in the context of the Ambient Assisted Living (AAL) Virgilius project, where users can navigate with a smartphone. This study is also a result of the research done in the context of the AAL EDLAH project, for optimizing the selection of the most adequate positioning technology. Accurate position estimations are used as input for the EDLAH object detection module.

F2D: A fall detection system tested with real data from daily life of elderly people, Panagiotis Kostopoulos, Tiago Nunes, Kevin Salvi, Michel Deriaz and Julien Torrent, in Proceedings of the seventeenth International Conference on E-health Networking, Application & Services (IEEE HealthCom'15), Boston, USA, October 2015.

Abstract. Falls among older people remain a very important public healthcare issue. Every year over 11 million falls are registered in the U.S. alone. This paper presents a practical real time fall detection system running on a smartwatch (F2D). A decision module takes into account the rebound after the fall and the residual movement of the user, matching a detected fall pattern to an actual fall. The final decision of a fall event is taken based on the location of the user. To the best of our knowledge, this is the first fall detection system which works on an independent smartwatch, being less stigmatizing for the end user. The fall detection algorithm has been tested by Fondation Suisse pour les Téléthèses (FST), the project partner who is responsible for the commercialization of our system. By analyzing real data of activities of daily life of elderly people, we are confident that F2D meets the demands of a reliable and easily extensible system. This paper highlights the innovative algorithm which takes into account the residual movement and the location of the user to increase the fall detection accuracy. By testing with real data we have a fall detection system ready to be deployed on the market.

Increased Fall Detection Accuracy in an Accelerometer-Based Algorithm Considering Residual Movement, Panagiotis Kostopoulos, Tiago Nunes, Kevin Salvi, Michel Deriaz and Julien Torrent, in Proceedings of the fourth International Conference on Pattern Recognition Applications and Methods (ICPRAM), Lisbon, Portugal, January 2015.

Abstract. Every year over 11 million falls are registered. Falls play a critical role in the deterioration of the health of the elderly and the subsequent need of care. This paper presents a fall detection system running on a smartwatch (F2D). Data from the accelerometer is collected, passing through an adaptive threshold-based algorithm which detects patterns corresponding to a fall. A decision module takes into account the residual movement of the user, matching a detected fall pattern to an actual fall. Unlike traditional systems which require a base station and an alarm central, F2D works completely independently. To the best of our knowledge, this is the first fall detection system which works on a smartwatch, being less stigmatizing for the end user. The fall detection algorithm has been tested by Fondation Suisse pour les Téléthèses (FST), the project partner for the commercialization of our system. Taking advantage of their experience with the end users, we are confident that F2D meets the demands of a reliable and easily extensible system. This paper highlights the innovative algorithm which takes into account residual movement to increase the fall detection accuracy and summarizes the architecture and the implementation of the fall detection system.

Accuracy Enhancements in Indoor Localization with the Weighted Average Technique, Grigorios G. Anagnostopoulos and Michel Deriaz, in Proceedings of the Eighth International Conference on Sensor Technologies and Applications (SENSORCOMM), Lisbon, Portugal, November 2014.

Abstract. Indoor localization is a topic that has drawn great attention over the last decade. One of the main goals of the research in the field is to improve the achieved accuracy. Along with the accuracy, factors like the easiness of deployment and reconfiguration, the cost, the computational complexity, and the ability to tune the desired accuracy in specific areas are also important. In this study, we used Bluetooth Low Energy (BLE) technology, that offers a low cost and is easily deployed and reconfigured. The weighted average method, combined with the selection of the closest beacons and the averaging of the received signal strength indication (RSSI) at the distance domain proposed in this paper, offers an accuracy down to 0.97 meters, depending on the deployment configuration. This method was tested in our lab and was following installed at the hospital in Perugia, Italy, in the context of the Ambient Assisted Living (AAL) Virgilius project, where users can navigate with a smartphone.

Improving Distance Estimation in Object Localisation with Bluetooth Low Energy, Georgia Ionescu, Carlos Martínez de la Osa and Michel Deriaz, in Proceedings of the Eighth International Conference on Sensor Technologies and Applications (SENSORCOMM), Lisbon, Portugal, November 2014.

Abstract. The arrival of Bluetooth Low Energy (BLE) creates opportunities for great innovations. One possible application is object localisation. We present our unique software that can track objects and help finding their location within a house perimeter. With the help of Bluetooth beacons that can be attached to different items, we can estimate the distance between the mobile device and the object with an accuracy of less than one meter. In this paper, we describe our system and the techniques we use, the experiments we conducted along with the results. In addition, we briefly present some work in progress using an indoor positioning system that helps locating the objects.

User Behaviour Recognition for Interacting with an Artistic Mobile Application, Jody Hausmann, Kevin Salvi, Jérôme Van Zaen, Adrian Hindle and Michel Deriaz, in Proceedings of the 4th International Conference on Multimedia Computing and Systems (ICMCS), Marrakesh, Morocco, April 2014.

Abstract. Interacting with smartphones generally requires direct input from the user. We investigated a novel way based on the user's behaviour to interact directly with a phone. In this paper, we present MoveYourStory, a mobile application that generates a movie composed of small video clips selected according to the user's position and his current behaviour when the user is moving. Towards this end, we have implemented an activity recognition module that is able to recognise current activities, like walking, bicycling or travelling in a vehicle using the accelerometer and the GPS embedded in a smartphone. Moreover, we added different walking intensity levels to the recognition algorithm, as well as the possibility of using the application in any position. A user study was done to validate our algorithm. Overall, we achieved 96.7% recognition accuracy for walking activities and 87.5% for the bicycling activity.

Gesture Recognition for Interest Detection in Mobile Applications, Jérôme Van Zaen, Jody Hausmann, Kevin Salvi and Michel Deriaz, in Proceedings of the 4th International Conference on Multimedia Computing and Systems (ICMCS), Marrakesh, Morocco, April 2014.

Abstract. Gestures are a fast and efficient mean to transmit information. They are used in a large number of situations where speaking is not as effective or even not possible, such as to indicate precisely a point of interest or to warn about a danger in a noisy environment. Furthermore, gestures can also be used for intuitive human-computer interfaces where specific tasks would otherwise require navigating through graphical interface menus. Consequently, solutions to provide reliable and accurate gesture recognition have been investigated extensively in the past years. In this paper, we propose a gesture recognition system to detect user interest with a sensor-embedded mobile phone. Specifically, this system uses hidden Markov models to recognize pointing gestures. Once such a gesture has been recognized, it is straightforward to identify the point of interest based on the user location and the phone orientation. In a subject-independent scenario, we obtained a recognition accuracy above 91% with the accelerometer when discriminating between pointing gestures and similar gestures that are common with a mobile phone (e.g. looking at the screen). When using the gyroscope in addition to the accelerometer, the accuracy raised above 98%.

On-board navigation system for smartphones, Mauricio Togneri and Michel Deriaz, in Proceedings of the 4th International Conference on Indoor Positioning and Indoor Navigation (IPIN), Montbéliard, France, October 2013.

Abstract. Several mobile solutions offer the possibility to download maps to use them offline at any moment. However, most of the time a connection to an external server is still needed in order to calculate routes and navigate. This represents an issue when traveling abroad due to roaming costs. In this paper, we propose a solution to this problem through an engine that stores and manages OpenStreetMap's data to consult points of interest, calculate routes and navigate without any connection required. The software manages indoor and outdoor information to provide a full navigation service that works in both environments. Therefore, the same system allows navigating in a highway by car and provides indoor navigation for museums, hospitals and airports among others. The result is an on-board engine for smartphones that provides indoor and outdoor navigation services that does not require Internet connection.

GeoGuild: Location-Based Framework for Mobile Games, Georgia Ionescu, Javier Martín de Valmaseda and Michel Deriaz, in Proceedings of the 3rd International Conference on Social Computing and Its Applications, Karlsruhe, Germany, October 2013.

Abstract. Smartphones' performance is in sustained growth, and their geolocation capabilities bring opportunities for developers to explore new aspects of social gaming. We propose a multiplatform framework that can give a social side to a wide range of mobile games. The framework is independent of the game and provides different location-based tools, such as guilds, territories management and geolocated events. Our set of tools integrates user geo-position on real world maps, allowing the players to team up and conquer territories in their vicinity. The uniqueness of our framework is the fact that it can turn a simple game into a full social experience, whilst combining the real and the virtual world. In this paper we provide an overview of our platform and show how well-established one-on-one games can be rethought as social multiplayer games.

TrustPos Model: Trusting in Mobile Users' Location, Javier Martín de Valmaseda, Georgia Ionescu and Michel Deriaz, in Proceedings of the 10th International Conference on Mobile Web Information Systems, Paphos, Cyprus, August 2013.

Abstract. While social games based on geo-location are gaining popularity, determining the authenticity of the players' geo-position becomes a challenge, since there are ways to counterfeit it, quite accessible to everyone. We propose a solution based on global spatial and temporal observation of the players' interactions. In this paper we present TrustPos, a trust engine model that associates a trustworthiness factor to each player based on the context of the interactions with both the game and other players. The novelty of TrustPos is the fact that our model is based on an internal network of players linked through their interactions, as opposed to previous approaches that are strongly specialized to concrete domains as peer-to-peer networks and social recommenders, not adaptable to location trust concerns.

Harmonization of Position Providers, Anja Bekkelien, Michel Deriaz, in Proceedings of the 3rd International Conference on Indoor Positioning and Indoor Navigation (IPIN), University of New South Wales, Sydney, Australia, November 2012.

Abstract. Hybrid positioning systems have been proposed in order to overcome the limitations of individual location sensing technologies. However, the large differences between the various technologies make integration into a larger system a challenge. This paper proposes a harmonization model which provides different location information sources with a uniform interface. The model creates an abstract representation based on performance criteria and our aim is to provide a basis for the design of location based services. The benefit of our approach is an extensible system that allows for seamless incorporation of new technologies. In addition, it offers a standard format for geographical positions, facilitating higher level treatment of information. To illustrate the usability of the model we implemented a prototype, the Global Positioning Module, which combines several commonly used technologies.

Hybrid Positioning Framework for Mobile Devices, Anja Bekkelien, Michel Deriaz, in Proceedings of the 2nd International Conference on Ubiquitous Positioning, Indoor Navigation, and Location Based Service (UPINLBS), Helsinki, Finland, October 2012.

Abstract. A variety of technologies has emerged in response to an increasing demand for location aware applications. Nevertheless, single-technology systems have several limitations and vulnerabilities and it seems unlikely that such a system will be able to provide a universal solution. In this paper, we present the Global Positioning Module (GPM), a framework that seamlessly combines a multitude of approaches in order to supply mobile devices with indoor and outdoor positioning. The novelty of our work is the way in which position providers are integrated by using an abstraction derived from their performance properties. This allows for a selection of providers based on their suitability to the surrounding environment and to the user's requirements with regards to accuracy, drift, power consumption and so on. Our aim is to provide a foundation for ubiquitous location based services, namely a transparent transition between the plethora of technologies available today.

Trust without Truth, Michel Deriaz. In IFIP International Federation for Information Processing, Volume 238, Trust Management, eds. Etalle, s., Marsch, S., (Boston: Springer), pp. 31-45, Canada, 2007.

Abstract. Can we trust without any reliable truth information? Most trust architectures work in a similar way: a trustor makes some observations, rates the trustee, and makes recommendations to his friends. When he faces a new case, he checks his trust table and uses recommendations given by trustworthy friends to decide whether he will undertake a given action. But what if the observations that are used to update the trust tables are wrong? How to deal with what we call the “uncertainty of the truth”? This paper presents how people that publish and remove virtual tags are able to create trust relations between them. A simulator as well as a concrete and widely deployed application have been used to validate our model. We observed good and encouraging results in general, but also some weaknesses, brought out through specific scenarios.

Trust and Security in Spatial Messaging: FoxyTag, the Speed Camera Case Study, Michel Deriaz, Jean-Marc Seigneur. In Proceedings of the 3rd International Conference on Privacy, Security and Trust, ACM, 2006.

Abstract. Current speed cameras alerting systems heavily rely on humans to check the trustworthiness of information sent by their users. Hence, these systems are often either expensive or suffer from drawbacks, such as incomplete information, for example, concerning mobile speed cameras. We propose an application called FoxyTag to address most of the previous issues by using a computational trust engine instead of human checks. FoxyTag lets any driver equipped with a Java/GPS enabled mobile phone post a virtual tag about a speed camera to notify other equipped drivers who can confirm or deny the (short-lived) presence of the (mobile) camera. The novel aspect of our trust engine is that it must be location and time aware to automatically compute the trustworthiness of the given tag. We have validated FoxyTag both in real-life settings and with a simulator for large-scale scenarios. The validation showed that our novel time-patterned trust metrics are appropriate.

Towards Trustworthy Spatial Messaging, Michel Deriaz, Jean-Marc Seigneur. In Proceedings of the Second International Workshop on Security and Trust Management, ERCIM, ENTCS, 2006.

Abstract. Spatial messaging is a term that defines the virtual publication of data in physical places. Generally, anyone in the neighborhood of such a publication point gets the message. Frameworks allowing the users to publish freely spatial messages already exist. However, the experiences realized with volunteers showed that there is only little interest in posting such notes. To our view, the main reason is that there are currently no trust and security mechanisms that inform about the trustworthiness of the messages, thus preventing any serious application. Filling this gap will promote the success of spatial messaging and the growing success of localization and mobile techniques will provide a good support for this concept. This paper describes the spatial messaging services that we are in the process to deploy with our new spatial messaging framework, which includes trust and security mechanisms.

A Social Semantic Infrastructure for Decentralised Systems Based on Specification-Carrying Code and Trust, Giovanna Di Marzo Serugendo, Michel Deriaz. In Proceedings of the Socially-Inspired Computing Workshop, pp. 143-152, D. Hales and B. Edmonds (Eds), Invited paper, 2005.

Abstract. Decentralised systems made of autonomous devices and software are gaining more and more interest. These autonomous elements usually do not know each other in advance and act without any central control. They thus form a society of devices and software, and as such need: basic interaction mechanisms for understanding each other, and a social infrastructure supporting interactions taking place in an uncertain environment. In an effort to go beyond pre-established communication schema and to cope with uncertainty, this paper proposes an interaction mechanism based exclusively: on semantic information expressed using specifications, and on a social infrastructure relying on trust and reputation.

Specification-Carrying Code for Self-Managed Systems, Giovanna Di Marzo Serugendo, Michel Deriaz. In IFIP/IEEE International Workshop on Self-Managed Systems and Services, 2005.

Abstract. This paper proposes the notion of Specification-Carrying Code as an interaction mechanism for self-assembly of autonomous decentralised software components. Each autonomous software entity incorporates more information than its operational behaviour, and publishes more data than its signature. The idea is to provide separately, for each entity, a functional part implementing its behaviour - the traditional program code; and an abstract description of the entity's functional behaviour and necessary parameters - a semantic behavioural description under the form of a formal specification. Interactions are exclusively based on the specifications and occur among entities with corresponding specifications. In the case of autonomic computing systems, in addition to functional aspects, the specification may carry a semantic description of non-functional information related to self-management. This paper presents the principles of the Specification-Carrying Code paradigm, the associated Service-Oriented Architecture, and it explains how self-managed systems can benefit from this paradigm.