Portrait of Dr Christos Efstratiou

Dr Christos Efstratiou

Senior Lecturer in Ubiquitous Computing
Chief Examinations Officer
Program Chair of MSc in Mobile Application Development


I am a Senior Lecturer in the School of Engineering and Digital Arts, University of Kent. Before joining Kent I was a Senior Research Associate at the University of Cambridge, a Research Associate at Lancaster University, and a Visiting Researcher at Sony Electronics Distributed Systems Lab. I received my PhD in Computer Science, from Lancaster University, UK. I hold an MSc (Distributed Systems) from Lancaster University and a BSc (Computer Engineering) from the University of Patras, Greece.

My main research interest lies in the general area of Ubiquitous Computing, with particular emphasis on the challenges of building multi-sensory computational systems to understand real-world human behaviour. My work involves the development of techniques to detect and model human activities using wearable or mobile sensing, IoT (Internet of Things) technologies, and passively captured human activity datasets.

My work has been funded by EPSRC, Innovate UK, EU Regional Development, the University of Kent, and a range of industrial partners. I have published more than 60 peer-reviewed papers, including papers that received the best-paper award at ACM Ubicomp 2014 and IEEE PerCom 2013. This body of work has so far generated more than 3,000 citations (h-index: 22).

I have served as member of technical program committees for a number of conferences, including IEEE PerCom, ACM Ubicomp, ACM MobiSys, ACM HotMobile. I was one of the co-founders and chair of the WristSense Workshop series and been a member of the organising committees of Ubicomp, MobiSys, HotMobile, PerCom.

Research interests

My main research interest lies in the general area of Ubiquitous Computing, with particular emphasis on the challenges of building multi-sensory computational systems to understand real-world human behaviour. My work focuses on the following topics:

  • Activity recognition: developing machine learning techniques to detect human activities using mobile/environmental sensors.
  • Data analytics: exploring patterns in human behaviour through the analysis of large datasets of human activity
  • IoT and Sensing technologies: develop systems where smart devices and wearable technologies can be used to understand human behaviour and interact with people.
  • Smart healthcare: use technologies to facilitate the monitoring and self-management of health conditions.

Human Activity and Behaviour recognition

Mobile and wearable technologies allow the capture of a range of sensing modalities that can reveal the activities of people. Data captured over long periods of time can allow the modelling of behavioural patterns and possible changes over time. In my work I have collaborated with healthcare specialists to apply such techniques for the monitoring of long term health conditions. For example, within the project “Epilepsy Networks” we explore the use of wearable wrist bands to detect the occurrence of seizures for people with epilepsy.

Social Sensing

The patterns of social interaction between people has been shown to be related to quality of life, the efficient collaboration of teams, and as indicator for potential mental health problems. In this line of work I explore the use of wearable sensing technologies, and passive environmental sensing for the accurate detection of social interactions. Significant results in this area include the analysis of how teams of people interact within an organisation, and how the building architecture can influence social patterns (output received the best paper award at Ubicomp’14).

IoT sensing infrastructure

With the proliferation of IoT technologies, multiple devices can capture snapshots of people’s daily activities. In this line of work I am interested in the technical challenges of developing a flexible IoT infrastructures that can passively track human activities. In my work I investigate the opportunities of fusing mobile and wearable sensing with sensing embedded in the environment (output received the best paper award at PerCom’14). My broader aim is to investigate the infrastructure requirements needed to support novel machine learning techniques (deep learning) within resource constraint devices, and the challenges in sharing IoT infrastructures with multiple users.

Current Projects

  • 2018 – 2020 (PI) Integrating healthcare IoT technologies and healthcare data analytics. Funded by Innovate UK.
  • 2018 – 2020 (CoI) Integrating data analytics with social planning mobile applications. Funded by Innovate UK.
  • 2017 – 2020 (CoI) Assistive Devices for Empowering Disabled People through robotic Technologies. Funded by Interreg (EU)
  • 2016 – 2020 (CoI) Empowerment of Disabled people through the User Co-creation of Assistive Technology. Funded by Interreg (EU).
  • 2016 – 2019 (PI) Data Analytics for Smart Healthcare. Funded by Shearwater Systems.

Past Projects

  • 2014 – 2016 (PI) Epilepsy Networks - Joined Up Thinking for Better Care. Funded by Innovate UK
  • 2015 – 2016 (CoI) RFID moisture sensor network for landslide monitoring. Funded by Newton Fund.


Undergraduate modules:

  • EL575 Mobile Application Development

Postgraduate modules:

  • EL881 Android Application Design
  • EL882 iOS Application Design
  • EL884 Mobile Application Project


I am looking for enthusiastic students who are interested in doing a PhD or Master by Research within the broader area of Ubiquitous computing. Please, feel free to email me your CV and a short description of your research interests.

Full Funding for PhD - starting 2019

Full scholarship available, covering home fees and a maintenance grant for a PhD, co-sponsored by EPSRC and MiiCare Ltd. Open for applications.

Deadline: Submit PhD application by February 8th 2019. Apply for an Electronic Engineering PhD online including your research proposal for this project.

Eligibility: Open to UK and EU applicants who have been resident in the UK for 3 years prior to commencement are eligible to apply.

Funding: Funding is available at the current home fee rate of £4,195.00 (rate for 2018/19) together with a maintenance grant of £14,777.00 (rate for 2018/19) 

Topic: Passive activity sensing for assistive leaving

Current state-of-the-art in assistive living relies on a combination of wearable sensing technologies (i.e. wrist-bands) and location tracking technologies embedded in the living environment. However, real-world deployments of wearable technologies for the elderly have had only limited success. In this project we aim to explore a new paradigm where the daily activities of people are monitored passively through sensing technologies that are embedded within the environment, without the need for any form of wearable device or active user intervention. Specifically, the aim of this project is to rely on a combination of embedded sensing technologies involving audio sensing, RF sensing and presence (PIR) sensing that work collaboratively to accurately track the daily activities of elderly participants. The work focuses on activities that are of particular importance for the wellbeing of the target users (e.g. fall detection, deterioration of physical mobility, abnormal behavioural patterns).

Research challenges that would be investigated are:

  • Audio sensing for activity detection: Employing deep learning models to identify changes in contextual activities performed at home.
  • Multi modal sensor fusion: Exploring the fusion of audio, RF sensing and presence sensing to accurate detect activities in shared environments with multiple occupants.
  • Passive sensing infrastructure: Explore the challenges of embedding passive sensing ML algorithms in resource constraint sensing devices.

Methodology: The project will involve the design, integration and deployment of prototype sensing infrastructure in lab conditions. This will enable the collection of data to train novel ML algorithms for passive sensing. Next, the developed system will be trialled in a real community deployment supported by the industrial partner miiCare Ltd. miiCare Ltd is currently involved in the deployment of assistive living technologies in Ebbsfleet Garden City.

Supervisor: Dr. Christos Efstratiou (C.Efstratiou@kent.ac.uk)

Co Supervisor: Prof. Ian McLoughlin (I.V.McLoughlin@kent.ac.uk)

Other Funding Opportunities

The School of Engineering and Digital Arts has a number of scholarships for PhD students, administered under the Graduate Teaching Assistant Scheme. Please, check the School’s pages for details


  • Regular TPC member of major international conferences, including ACM Ubicomp, ACM MobiSys, IEEE PerCom, ACM HotMobile.
  •  Regular reviewer for journals including Transactions in Mobile Computing, IEEE Pervasive.
  • Grant Reviewer and Panellist for EPSRC (2017, 2018)


Showing 50 of 54 total publications in the Kent Academic Repository. View all publications.


  • Intarasirisawat, J., Ang, C., Efstratiou, C., Dickens, L., Sriburapar, N., Sharma, D. and Asawathaweeboon, B. (2020). An Automated Mobile Game-based Screening Tool for Patients with Alcohol Dependence. Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies [Online] 4. Available at: https://doi.org/10.1145/3411837.
    Traditional methods for screening and diagnosis of alcohol dependence are typically administered by trained clinicians in medical settings and often rely on interview responses. These self-reports can be unintentionally or deliberately false, and misleading answers can, in turn, lead to inaccurate assessment and diagnosis. In this study, we examine the use of user-game interaction patterns on mobile games to develop an automated diagnostic and screening tool for alcohol-dependent patients. Our approach relies on the capture of interaction patterns during gameplay, while potential patients engage with popular mobile games on smartphones. The captured signals include gameplay performance, touch gestures, and device motion, with the intention of identifying patients with alcohol dependence. We evaluate the classification performance of various supervised learning algorithms on data collected from 40 patients and 40 age-matched healthy adults. The results show that patients with alcohol dependence can be automatically identified accurately using the ensemble of touch, device motion, and gameplay performance features on 3-minute samples (accuracy=0.95, sensitivity=0.95, and specificity=0.95). The present findings provide strong evidence suggesting the potential use of user-game interaction metrics on existing mobile games as discriminant features for developing an implicit measure to identify alcohol dependence conditions. In addition to supporting healthcare professionals in clinical decision-making, the game-based self-screening method could be used as a novel strategy to promote alcohol dependence screening, especially outside of clinical settings.
  • Intarasirisawat, J., Ang, C., Efstratiou, C., Dickens, L. and Page, R. (2019). Exploring the Touch and Motion Features in Game-Based Cognitive Assessments. Journal of Interactive, Mobile, Wearable and Ubiquitous Technologies [Online] 3. Available at: http://dx.doi.org/10.1145/3351245.
    Early detection of cognitive decline is important for timely intervention and treatment strategies to prevent further dete- rioration or development of more severe cognitive impairment, as well as identify at risk individuals for research. In this paper, we explore the feasibility of using data collected from built-in sensors of mobile phone and gameplay performance in mobile-game-based cognitive assessments. Twenty-two healthy participants took part in the two-session experiment where they were asked to take a series of standard cognitive assessments followed by playing three popular mobile games in which user-game interaction data were passively collected. The results from bivariate analysis reveal correlations between our proposed features and scores obtained from paper-based cognitive assessments. Our results show that touch gestural interaction and device motion patterns can be used as supplementary features on mobile game-based cognitive measurement. This study provides initial evidence that game related metrics on existing off-the-shelf games have potential to be used as proxies for conventional cognitive measures, specifically for visuospatial function, visual search capability, mental flexibility, memory and attention.
  • Nawaz, S., Efstratiou, C. and Mascolo, C. (2016). Smart Sensing Systems for the Daily Drive. IEEE Pervasive Computing [Online] 15:39-43. Available at: http://www.dx.doi.org/10.1109/MPRV.2016.22.
    When driving, you might sometimes wonder, "Are there any disruptions on my regular route that might delay me, and will I be able to find a parking space when I arrive?" Two smartphone-based prototype systems can help answer these questions. The first is ParkSense, which can be used to sense on-street parking-space occupancy when coupled with electronic parking payment systems. The second system can sense and recognize a user's repeated car journeys, which can be used to provide personalized alerts to the user. Both systems aim to minimize the impact of sensing tasks on the device's lifetime so that the user can continue to use the device for its primary purpose. This department is part of a special issue on smart vehicle spaces.
  • Efstratiou, C., Rachuri, K. and Das, S. (2015). IEEE PerCom 2015. IEEE Pervasive Computing [Online] 14:84-88. Available at: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7140687.
    The 2015 IEEE International Conference on Pervasive Computing and Communications (PerCom 2015) was held in Saint Louis, Missouri. With 13 years of history, PerCom has become one of the premier venues for ubiquitous computing research. Several cutting-edge workshops ran in parallel on March 23rd and 27th, while the main conference took place March 24–26th as a single-track event.
  • Rachuri, K., Efstratiou, C., Leontiadis, I., Mascolo, C. and Rentfrow, P. (2014). Smartphone sensing offloading for efficiently supporting social sensing applications. Pervasive and Mobile Computing [Online] 10:3-21. Available at: http://dx.doi.org/10.1016/j.pmcj.2013.10.005.
    Mobile phones play a pivotal role in supporting ubiquitous and unobtrusive sensing of human activities. However, maintaining a highly accurate record of a user’s behavior throughout the day imposes significant energy demands on the phone’s battery. In this work, we investigate a new approach that can lead to significant energy savings for mobile applications that require continuous sensing of social activities. This is achieved by opportunistically offloading sensing to sensors embedded in the environment, leveraging sensing that may be available in typical modern buildings (e.g., room occupancy sensors, RFID access control systems).

    In this article, we present the design, implementation, and evaluation of METIS: an adaptive mobile sensing platform that efficiently supports social sensing applications. The platform implements a novel sensor task distribution scheme that dynamically decides whether to perform sensing on the phone or in the infrastructure, considering the energy consumption, accuracy, and mobility patterns of the user. By comparing the sensing distribution scheme with sensing performed solely on the phone or exclusively on the fixed remote sensors, we show, through benchmarks using real traces, that the opportunistic sensing distribution achieves over 60% and 40% energy savings, respectively. This is confirmed through a real world deployment in an office environment for over a month: we developed a social application over our frameworks, that is able to infer the collaborations and meetings of the users. In this setting the system preserves over 35% more battery life over pure phone sensing.
  • Friday, A., Davies, N. and Efstratiou, C. (2012). Reflections on Long-Term Experiments with Public Displays. IEEE Computer 45:34-41.
  • Büscher, M., Coulton, P., Efstratiou, C., Gellersen, H., Hemment, D., Mehmood, R. and Sangiorgi, D. (2009). Intelligent Mobility Systems: Some Socio-technical Challenges and Opportunities. Communications Infrastructure. Systems and Applications in Europe [Online] 16:140-152. Available at: http://dx.doi.org/10.1007/978-3-642-11284-3_15.
    Analysis of socio-technical challenges and opportunities around contemporary mobilities suggests new interpretations and visions for intelligent transport systems. Multiple forms of intelligence are required (but not easily compatible), transport is too narrow a term, and innovation results in new socio-technical systems. An exploration of cumulative, collective and collaborative aspects of mobility systems, allows us to sketch challenges and opportunities in relation to practices of collaboration, communication and coordination, literacies for creativity, comfort and control, citizenship and (lack of) a sense of crisis, concluding with a discussion of methodological implications.
  • Cheverst, K., Davies, N., Mitchell, K. and Efstratiou, C. (2001). Using Context as a Crystal Ball: Rewards and Pitfalls. Personal and Ubiquitous Computing [Online] 5:8-11. Available at: http://dx.doi.org/10.1007/s007790170020.
    Context-awareness can be used to simplify a user’s understanding of, and interaction with, interactive systems. In effect, through adaptation, context-aware systems can migrate complexity away from the user and into the system (or agent). However, the incorporation of context-awareness raises a number of issues. For example, users are required to trust the behaviour of the system’s intelligence and this requires the system to have predictable behaviour and the ability to successfully and consistently preempt the user’s goal. Unfortunately, the agent may incorrectly preempt the user’s goal, owing to either flawed intelligence or to incorrect or out-of-date contextual information. In such circumstances the user is likely to feel frustration because the system will either appear overly prescriptive or, worse still, present incorrect results. This paper considers these issues, a number of which are described in anecdotal form, based on our experiences in developing and evaluating the context-aware GUIDE system

Book section

  • Mzurikwao, D., Williams Samuel, O., Grace Asogbon, M., Li, X., Li, G., Yeo, W., Efstratiou, C. and Siang Ang, C. (2019). A Channel Selection Approach Based on Convolutional Neural Network for Multi-channel EEG Motor Imagery Decoding. In: 2019 IEEE Second International Conference on Artificial Intelligence and Knowledge Engineering (AIKE). New York, USA: IEEE, pp. 195-202. Available at: https://doi.org/10.1109/AIKE.2019.00042.
    For many disabled people, brain computer interface (BCI) may be the only way to communicate with others and to control things around them. Using motor imagery paradigm, one can decode an individual's intention by using their brainwaves to help them interact with their environment without having to make any physical movement. For decades, machine learning models, trained on features extracted from acquired electroencephalogram (EEG) signals have been used to decode motor imagery activities. This method has several limitations and constraints especially during feature extraction. Large number of channels on the current EEG devices make them hard to use in real-life as they are bulky, uncomfortable to wear, and takes lot of time in preparation. In this paper, we introduce a technique to perform channel selection using convolutional neural network (CNN) and to decode multiple classes of motor imagery intentions from four participants who are amputees. A CNN model trained on EEG data of 64 channels achieved a mean classification accuracy of 99.7% with five classes. Channel selection based on weights extracted from the trained model has been performed with subsequent models trained on eight selected channels achieved a reasonable accuracy of 91.5%. Training the model in time domain and frequency domain was also compared, different window sizes were experimented to test the possibilities of realtime application. Our method of channel selection was then evaluated on a publicly available motor imagery EEG dataset.
  • Lee, J., Efstratiou, C. and Bai, L. (2016). OSN Mood Tracking: Exploring the Use of Online Social Network Activity as an Indicator of Mood Changes. In: Proceedings of the 2016 ACM International Joint Conference on Pervasive and Ubiquitous Computing: Adjunct. New York, USA: ACM, pp. 1171-1179. Available at: https://dx.doi.org/10.1145/2968219.2968304.
    Online social networks (OSNs) have become an integral part of our everyday lives, where we share our thoughts and feelings. This study analyses the extent to which the changes of an individual’s real-world psychological mood can be inferred by tracking their online activity on Facebook and Twitter. By capturing activities from the OSNs and ground truth data via experience sampling, it was found that mood changes can be detected within a window of 7 days for 61% of the participants by using specific, combined online activity signals. The participants fall into three distinct groups: those whose mood correlates positively with their online activity, those who correlate negatively and those who display a weak correlation. We trained two classifiers to identify these groups using features from their online activity, which achieved precision of 95.2% and 84.4% respectively. Our results suggest that real-world mood changes can be passively tracked through online activity on OSNs.
  • Brown, C., Efstratiou, C., Leontiadis, I., Quercia, D., Mascolo, C., Scott, J. and Key, P. (2014). The Architecture of Innovation: Tracking Face-to-Face Interactions with UbiComp Technologies. In: Proceedings of the 2014 ACM Joint Conference on Pervasive and Ubiquitous Computing. New York, USA: Association for Computing Machinery, pp. 811-822. Available at: http://dx.doi.org/10.1145/2632048.2632056.
    The layouts of the buildings we live in shape our everyday lives. In office environments, building spaces affect employees’ communication, which is crucial for productivity and innovation. However, accurate measurement of how spatial layouts affect interactions is a major challenge and traditional techniques may not give an objective view.
    We measure the impact of building spaces on social inter- actions using wearable sensing devices. We study a single organization that moved between two different buildings, affording a unique opportunity to examine how space alone can affect interactions. The analysis is based on two large scale deployments of wireless sensing technologies: short-range, lightweight RFID tags capable of detecting face-to-face interactions. We analyze the traces to study the impact of the building change on social behavior, which represents a first example of using ubiquitous sensing technology to study how the physical design of two workplaces combines with organizational structure to shape contact patterns.
  • Brown, C., Efstratiou, C., Leontiadis, I., Quercia, D. and Mascolo, C. (2014). Tracking serendipitous interactions: how individual cultures shape the office. In: Proceedings of the 17th ACM Conference on Computer Supported Cooperative Work & Social Computing. New York, USA: ACM, pp. 1072-1081. Available at: http://dx.doi.org/10.1145/2531602.2531641.
    In many work environments, serendipitous interactions between members of different groups may lead to enhanced productivity, collaboration and knowledge dissemination. Two factors that may have an influence on such interactions are cultural differences between individuals in highly multicultural workplaces, and the layout and physical spaces of the workplace itself. In this work, we investigate how these two factors may facilitate or hinder inter-group interactions in the workplace. We analyze traces collected using wearable electronic badges to capture face-to-face interactions and mobility patterns of employees in a research laboratory in the UK. We observe that those who interact with people of different roles tend to come from collectivist cultures that value relationships and where people tend to be comfortable with social hierarchies, and that some locations in particular are more likely to host serendipitous interactions, knowledge that could be used by organizations to enhance communication and productivity.
  • Nawaz, S., Efstratiou, C., Mascolo, C. and Soga, K. (2012). Social sensing in the field: challenges in detecting social interactions in construction sites. In: Proceedings of the 1st ACM Workshop on Mobile Systems for Computational Social Science. New York, USA: ACM, pp. 28-32. Available at: http://dx.doi.org/10.1145/2307863.2307872.
    Construction industry is a sector that is renowned for the slow uptake of new technologies. This is usually due to the conservative nature of this sector that relies heavily on tried and tested and successful old business practices. However, there is an eagerness in this industry to adopt Building Information Modelling (BIM) technologies to capture and record accurate information about a building project. But vast amounts of information and knowledge about the construction process is typically hidden within informal social interactions that take place in the work environment. In this paper we present a vision where smartphones and tablet devices carried by construction workers are used to capture the interaction and communication between workers in the field. Informal chats about decisions taken in the field, impromptu formation of teams, identification of key persons for certain tasks, and tracking the flow of information across the project community, are some pieces of information that could be captured by employing social sensing in the field. This information can not only be used during the construction to improve the site processes but it can also be exploited by the end user during maintenance of the building. We highlight the challenges that need to be overcome for this mobile and social sensing system to become a reality.
  • Hossmann, T., Efstratiou, C. and Mascolo, C. (2012). Collecting big datasets of human activity one checkin at a time. In: Proceedings of the 4th ACM International Workshop on Hot Topics in Planet-Scale Measurement. New York, USA: ACM, pp. 15-20. Available at: http://dx.doi.org/10.1145/2307836.2307842.
    A variety of cutting edge applications for mobile phones exploit the availability of phone sensors to accurately infer the user activity and location to offer more effective services. To validate and evaluate these new applications, appropriate and extensive datasets are needed: in particular, large sets of traces of sensor data (accelerometer, GPS, micro- phone, etc.), labelled with corresponding user activities. So far, such traces have only been collected in short-lived, small-scale setups. The primary reason for this is the difficulty in establishing accurate ground truth information outside the laboratory. Here, we present our vision of a system for large-scale sensor data capturing, leveraging all sensors of todays smart phones, with the aim of generating a large dataset that is augmented with appropriate ground-truth information. The primary challenges that we address consider the energy cost on the mobile device and the incentives for users to keep running the system on their device for longer. We argue for leveraging the concept of the checkin - as successfully introduced in online social networks (e.g. Foursquare) - for collecting activity and context related datasets. With a checkin, a user deliberately provides a small piece of data about their behaviour while enabling the system to adjust sensing and data collection around important activities.

    In this work we present up2, a mobile app letting users check in to their current activity (e.g., "waiting for the bus", "riding a bicycle", "having dinner"). After a checkin, we use the phone's sensors (GPS, accelerometer, microphone, etc.) to gather data about the user's activity and surrounding. This makes up2 a valuable tool for research in sensor based activity detection.
  • Leontiadis, I., Efstratiou, C., Picone, M. and Mascolo, C. (2012). Don’t kill my ads! balancing privacy in an ad-supported mobile application market. In: Proceedings of the Twelfth Workshop on Mobile Computing Systems & Applications. New York, USA: ACM, pp. 1-6. Available at: http://dx.doi.org/10.1145/2162081.2162084.
    Application markets have revolutionized the software download model of mobile phones: third-party application developers offer software on the market that users can effortlessly install on their phones. This great step forward, however, also imposes some threats to user privacy: applications often ask for permissions that reveal private information such as the user's location, contacts and messages. While some mechanisms to prevent leaks of user privacy to applications have been proposed by the research community, these solutions fail to consider that application markets are primarily driven by advertisements that rely on accurately profiling the user. In this paper we take into account that there are two parties with conflicting interests: the user, interested in maintaining their privacy and the developer who would like to maximize their advertisement revenue through user profiling. We have conducted an extensive analysis of more than 250,000 applications in the Android market. Our results indicate that the current privacy protection mechanisms are not effective as developers and advert companies are not deterred. Therefore, we designed and implemented a market-aware privacy protection framework that aims to achieve an equilibrium between the developer's revenue and the user's privacy. The proposed framework is based on the establishment of a feedback control loop that adjusts the level of privacy protection on mobile phones, in response to advertisement generated revenue.
  • Leontiadis, I., Efstratiou, C., Mascolo, C. and Crowcroft, J. (2012). SenShare: Transforming Sensor Networks into Multi-application Sensing Infrastructures. In: Wireless Sensor Networks. Berlin, Germany: Springer, pp. 65-81. Available at: http://dx.doi.org/10.1007/978-3-642-28169-3_5.
    Sensor networks are typically purpose-built, designed to support a single running application. As the demand for applications that can harness the capabilities of a sensor-rich environment increases, and the availability of sensing infrastructure put in place to monitor various quantities soars, there are clear benefits in a model where infrastructure can be shared amongst multiple applications. This model however introduces many challenges, mainly related to the management of the communication of the same application running on different network nodes, and the isolation of applications within the network. In this work we present SenShare, a platform that attempts to address the technical challenges in transforming sensor networks into open access infrastructures capable of supporting multiple co-running applications. SenShare provides a clear decoupling between the infrastructure and the running application, building on the concept of overlay networks. Each application operates in an isolated environment consisting of an in-node hardware abstraction layer, and a dedicated overlay sensor network. We further report on the deployment of SenShare within our building, which presently supports the operation of multiple sensing applications, including office occupancy monitoring and environmental monitoring.
  • Buscher, M., Coulton, P., Efstratiou, C., Gellersen, H. and Hemment, D. (2012). Connected, computed, collective: Smart Mobilities. In: Grieco, M. and Urry, J. eds. Mobilities: New Perspectives on Transport and Society. Ashgate, pp. 135-158.
    The 'smart' in 'Smart Transport' usually refers to technologies, not people. From cars designed to be 'stackable', through signs that monitor parking spaces, to 'automatic cruise control' systems that 'intelligently' control distances through vehicle-to-vehicle and vehicle-to-infrastructure communication: technologies are key to smart transport. And it is true, people — armoured with status symbol cars and stuck in traffic — often do not behave intelligently, raging at other drivers and pedestrians, taking risks that endanger themselves and others. However, underestimating human intelligence could be a damaging oversight and missed opportunity for transport designers. In this chapter we examine several related aspects of human sense-making practices on the move and explore how these could be productively integrated with smart transport. Starting with a comparison of a 'view from above' and a 'view from on the ground', key aspects of the social logics of our mobile societies become visible. Then, new technologies are already an integral part of the social organisation of mobilities — with some socio-technical innovations that form a kind of parallel universe to the intelligent transport solutions envisaged by engineers and traffic planners. We discuss such 'alternate smart mobilities' through some utopian visions of 'collective intelligence' (Levy 1997) and its more mundane manifestations, including micro-coordination and an emergent digital economy of mobilities, based on crowdsourcing, community sensing, and data mashups. These 'bottom-up' innovations could come together productively with the pervasive 'qualculation' (Thrift 2004) that underpins traffic shaping and other engineering and design efforts around 'intelligent transport systems' (ITS) (COM 2008). Moreover, such a convergence of social and technological innovation could counteract the threat of 'Orwellian' surveillance that is part of a potentially Faustian bargain for more efficiency, convenience, sustainability and security in transport (Dennis and Urry 2009). We conclude with suggestions for mixed mobile research methods that can inform innovation.
  • Vallina-Rodriguez, N., Efstratiou, C., Xie, G. and Crowcroft, J. (2011). Enabling opportunistic resources sharing on mobile operating systems: benefits and challenges. In: Proceedings of the 3rd ACM Workshop on Wireless of the Students, by the Students, for the Students. New York, USA: ACM, pp. 29-32. Available at: http://dx.doi.org/10.1145/2030686.2030696.
    The intense use of hardware resources by mobile applications has a significant impact on the battery life of mobile devices. In this paper we introduce a novel approach for the efficient use of mobile phone resources, by considering the coordinated sharing of resources offered by multiple co-located devices. Taking into account the social behaviour of users, there are frequent situations where similar resources are available by co-located mobile phones. In this work we discuss the feasibility of sharing such resources in an opportunistic way, the possible benefits and the research challenges that need to be addressed in order to implement a reliable and robust solution.
  • Efstratiou, C., Leontiadis, I., Mascolo, C. and Crowcroft, J. (2010). A shared sensor network infrastructure. In: Proceedings of the 8th ACM Conference on Embedded Networked Sensor Systems. New York, USA: ACM, pp. 367-368. Available at: http://dx.doi.org/10.1145/1869983.1870026.
    An increasing number of sensor networks have been deployed to monitor a variety of conditions and situations. At the same time, more and more applications are starting to rely on the data from sensor networks to provide users with (near) real-time information and conditions. This increasing demand of users for accurate information about natural and surrounding phoenomena is creating a business case for application providers.
  • Kriegel, J., Jehle, F., Efstratiou, C., Zaad, L., Heppner, J. and Hupp, J. (2009). Smart Design for Human Performance in the Office of the Future – Requirements towards Services and Technical Advises for Tomorrows Office Work. In: Constructing Ambient Intelligence AmI 2008 Workshops. Berlin, Germany: Springer, pp. 1-5. Available at: http://dx.doi.org/10.1007/978-3-642-10607-1_1.
    The office of the future is a synonym of today’s needs and expectations towards prospective solutions and services which can support human performance in the future office work. The development of such future services is on one hand affected by the technical possibilities and on the other by the demands of changing and global work environment. The process of generating successful services can be initiated by creative methods. The 635 method is a creative brain writing technique, which follows the problem solving circle to create new uncommon ideas in a group of expert or user participants. The workshop on smart design for human performance in the office of the future used the 635 method to identify requirements towards services and technical advises for tomorrows office work. The outcome of the written brainstorming is a list of different criteria and examples which describe the several dimensions of needs and demands towards the office of the future.
  • Fitton, D., Sundramoorthy, V., Kortuem, G., Brown, J., Efstratiou, C., Finney, J. and Davies, N. (2008). Exploring the Design of Pay-Per-Use Objects in the Construction Domain. In: Smart Sensing and Context Third European Conference. Berlin, Germany: Springer, pp. 192-205. Available at: http://dx.doi.org/10.1007/978-3-540-88793-5_15.
    Equipment used in the construction domain is often hired in order to reduce cost and maintenance overhead. The cost of hire is dependent on the time period involved and does not take into account the actual use equipment has received. This paper presents our initial investigation into how physical objects augmented with sensing and communication technologies can measure use in order to enable new pay-per-use payment models for equipment hire. We also explore user interaction with pay-per-use objects via mobile devices. The user interactions that take place within our prototype scenario range from simple information access to transactions involving multiple users. This paper presents the design, implementation and evaluation of a prototype pay-per-use system motivated by a real world equipment hire scenario. We also provide insights into the various challenges introduced by supporting a pay-per-use model, including data storage and data security in addition to user interaction issues.
  • Brown, J., Finney, J., Efstratiou, C., Green, B., Davies, N., Lowton, M. and Kortuem, G. (2007). Network interrupts: supporting delay sensitive applications in low power wireless control networks. In: CHANTS ’07 Proceedings of the Second ACM Workshop on Challenged Networks. New York, USA: ACM, pp. 51-58. Available at: http://dx.doi.org/10.1145/1287791.1287802.
    The importance in maintaining energy efficient communications in low power networks such as sensor and actuator networks is well understood. However, in recent years, a growing number of delay sensitive and interactive applications have been discovered for such networks, that are no longer purely limited to the data gathering model of sensor networks. Providing support application requiring low latency interaction in such environments without negatively affecting energy efficiency remains a challenging problem. This paper outlines the importance of this emerging class of application, discusses problems involved in supporting them in energy challenged environments, proposes a combined hardware and software mechanism based on heterogeneous wireless networking which works toward solving this problem, and goes on to evaluate this mechanism through experimental analysis. The paper concludes with a discussion of the applicability of the mechanism to typical application scenarios.
  • Efstratiou, C., Davies, N., Kortuem, G., Finney, J., Hooper, R. and Lowton, M. (2007). Experiences of Designing and Deploying Intelligent Sensor Nodes to Monitor Hand-Arm Vibrations in the Field. In: MobiSys ’07 Proceedings of the 5th International Conference on Mobile Systems, Applications and Services. New York, USA: ACM, pp. 127-138. Available at: http://dx.doi.org/10.1145/1247660.1247677.
    The NEMO project is exploring the use of mobile sensor nodes to augment physical work artefacts in order to ensure compliance with health and safety regulations. In this paper we present our experiences of designing and deploying the NEMO Hand Arm Vibration (HAV) monitoring system. Long term exposure to hand arm vibration can lead to serious health conditions and the NEMO HAV monitoring system offers an integrated architecture for capturing HAV exposure data in the field, providing feedback about exposure levels both in the field and as input to a back-end database. Our design allows health and safety regulations specified at the enterprise level to be embedded within the wireless sensor nodes allowing them to operate without any infrastructural support. The system has been the subject of a two week field trial that took place with the collaboration of a British construction and maintenance company. During the field trial, the NEMO HAV system was deployed to a road maintenance patching gang and data was collected on HAV exposure caused by hydraulic drills. The paper reports on the results of the field trial and the lessons learned through the real deployment of the system.
  • Davies, N., Efstratiou, C., Finney, J., Hooper, R., Kortuem, G. and Lowton, M. (2007). Sensing Danger - Challenges in Supporting Health and Safety Compliance in the Field. In: Eighth IEEE Workshop on Mobile Computing Systems and Applications. IEEE, pp. 34-38. Available at: http://dx.doi.org/10.1109/HotMobile.2007.7.
    Many workers operate in environments that are inherently hazardous and that are subject to strict health and safety rules and regulations. We envisage a world in which physical work artefacts such as tools, are augmented with intelligent mobile nodes that are able to observe the working activities taking place, evaluate compliance with health and safety regulations and assist or actively enforce compliance with these regulations. This vision creates a new field of work in the area of health and safety aware intelligent mobile sensor networks. In this paper we describe a number of new challenges faced when developing mobile systems for compliance with health and safety regulations.
  • Kortuem, G., Alford, D., Ball, L., Busby, J., Davies, N., Efstratiou, C., Finney, J., White, M. and Kinder, K. (2007). Sensor Networks or Smart Artifacts? An Exploration of Organizational Issues of an Industrial Health and Safety Monitoring System. In: UbiComp 2007: Ubiquitous Computing 9th International Conference. Berlin, Germany: Springer, pp. 465-482. Available at: http://dx.doi.org/10.1007/978-3-540-74853-3_27.
    Industrial health and safety is an important yet largely unexplored application area of ubiquitous computing. In this paper we investigate the relationship between technology and organization in the context of a concrete industrial health and safety system. The system is designed to reduce the number of incidents of “vibration white finger” (VWF) at construction sites and uses wireless sensor nodes for monitoring workers’ exposure to vibrations and testing of compliance with legal health and safety regulations. In particular we investigate the impact of this ubiquitous technology on the relationship between management and operatives, the formulation of health and safety rules and the risk perception and risk behavior of operatives. In addition, we contrast sensor-network inspired and smart artifact inspired compliance systems, and make the case that these technology models have a strong influence on the linkage between technology and organization.
  • Efstratiou, C., Friday, A., Davies, N. and Cheverst, K. (2002). Utilising the event calculus for policy driven adaptation on mobile systems. In: Proceedings Third International Workshop on Policies for Distributed Systems and Networks. IEEE, pp. 13-24. Available at: http://dx.doi.org/10.1109/POLICY.2002.1011289.
    Adaptation is an important requirement for mobile applications due to the varying levels of resource availability that characterises mobile environments. However, without proper control, multiple applications can each adapt independently in response to a range of different adaptive stimuli, causing conflicts or suboptimal performance. In this paper, we present a policy-driven approach for mobile adaptive systems that can overcome the aforementioned problems. Our system is based on a policy language derived from the event calculus logic programming formalism. Important characteristics of our policy language are its support for explicit time-dependency expressions and its simple and user-friendly syntax.
  • Efstratiou, C., Friday, A., Davies, N. and Cheverst, K. (2002). A platform supporting coordinated adaptation in mobile systems. In: Proceedings Fourth IEEE Workshop on Mobile Computing Systems and Applications. IEEE, pp. 128-137. Available at: http://dx.doi.org/10.1109/MCSA.2002.1017492.
    Mobile environments are highly dynamic, characterised by frequent and sudden changes in resource availability. As a consequence, adaptive mobile applications need to be capable of adapting their behaviour to ensure they continue to offer the best possible level of service to the user. Our experience of developing such applications has led us to believe that existing mobile middleware platforms fail to consider adaptive applications on a host as an ensemble of entities competing for the same resources; instead, focusing on the requirements of each application in isolation. A new approach is required which offers the mechanisms to support coordination of the adaptive behaviour of multiple applications in order to achieve a common goal. We present a platform designed to meet this objective. Our platform is based on the notion of the definition of system-wide flexible adaptation policies written using a form of Kowalsky's (1992) event calculus, that may be adapted according to user needs. Moreover, we also believe that by using our approach it will soon be possible to identify and resolve conflicts caused by the need to adapt to multiple contextual triggers.
  • Efstratiou, C., Cheverst, K., Davies, N. and Friday, A. (2001). An Architecture for the Effective Support of Adaptive Context-Aware Applications. In: Mobile Data Management Second International Conference. Berlin, Germany: Springer, pp. 15-26. Available at: http://dx.doi.org/10.1007/3-540-44498-X_2.
    Mobile applications are required to operate in environments characterised by change. More specifically, the availability of resources and services may change significantly during a typical period of system operation. As a consequence, adaptive mobile applications need to be capable of adapting to these changes to ensure they offer the best possible level of service to the user. Our experiences of developing and evaluating adaptive context-aware applications in mobile environments has led us to believe that existing architectures fail to provide the necessary support for such applications. In this paper, we discuss the shortcomings of existing approaches and present work on our own architecture that has been designed to meet the key requirements of context-aware adaptive applications.

Conference or workshop item

  • Bai, L., Yeung, C., Efstratiou, C. and Chikomo, M. (2019). Motion2Vector: Unsupervised Learning in Human Activity Recognition Using Wrist-Sensing Data. In: CPD 2019: THE 2nd Workshop on Combining Physical and Data-Driven Knowledge in Ubiquitous Computing, in Conjunction With Ubicomp’19.
    With the increasing popularity of consumer wearable devices augmented with sensing capabilities (smart bands, smart watches), there is a significant focus on extracting meaningful information about human behaviour through large scale real-world wearable sensor data. The focus of this work is to develop techniques to detect human activities, utilising a large dataset of wearable data where no ground truth has been produced on the actual activities performed. We propose a deep learning variational auto encoder activity recognition model - Motion2Vector. The model is trained using large amounts of unlabelled human activity data to learn a representation of a time period of activity data. The learned activity representations can be mapped into an embedded activity space and grouped with regards to the nature of the activity type. In order to evaluate the proposed model, we have applied our method on public dataset - The Heterogeneity Human Activity Recognition (HHAR) dataset. The results showed that our method can achieve improved result over the HHAR dataset. In addition, we have collected our own lab-based activity dataset. Our experimental results show that our system achieves good accuracy in detecting such activities, and has the potential to provide additional insights in understanding the real-world activity in the situations where there is no ground truth available.
  • Baker, J. and Efstratiou, C. (2017). Next2Me: Capturing Social Interactions through Smartphone Devices using WiFi and Audio signals. In: EAI International Conference on Mobile and Ubiquitous Systems: Computing, Networking and Services (MobiQuitous 2017). ACM, pp. 412-421. Available at: http://dx.doi.org/10.1145/3144457.3144500.
    Typical approaches in detecting social interactions consider the use of co-location as a proxy for real-world interactions. Such approaches can underperform in challenging situations where multiple social interactions can occur in close proximity to each other. In this paper, we present a novel approach to detect co-located social interactions using smartphones. Next2Me relies on the use of WiFi signals and audio signals to accurately distinguish social groups interacting within a few meters from each other. Through a range of real-world experiments, we demonstrate a technique that utilises WiFi fingerprinting, along with sound fingerprinting to identify social groups. Experimental results show that Next2Me can achieve a precision of 88% within noisy environments, including smartphones that are placed in users’ pockets, whilst maintaining a very low energy footprint (<3% of battery capacity per day).
  • Nicholls, B., Ang, C., Efstratiou, C., Lee, Y. and Yeo, W. (2017). Swallowing detection for game control: using skin-like electronics to support people with dysphagia. In: IEEE PerCom Workshop on Pervasive Health Technologies. IEEE. Available at: http://dx.doi.org/10.1109/PERCOMW.2017.7917598.
    In this paper, we explore the feasibility of developing a sensor-driven rehabilitation game for people suffering from dysphagia. This study utilizes the skin-like electronics for unobtrusive, comfortable, continuous recording of surface electromyograms (EMG) during swallowing and use them for driving game-based, user-controlled feedback. The experimental study includes the development and evaluation of a real-time swallow detection algorithm using skin-like sensors and a game-based human-computer interaction. The user evaluations support the ease of use of the skin-like electronics as a motivational tool for people with dysphagia.
  • Bai, L., Efstratiou, C. and Ang, C. (2016). weSport: Utilising Wrist-Band Sensing to Detect Player Activities in Basketball Games. In: WristSense 2016: Workshop on Sensing Systems and Applications Using Wrist Worn Smart Devices (co-Located With IEEE PerCom 2016). Available at: https://sites.google.com/site/wristsenseworkshop2016/.
    Wristbands have been traditionally designed to track the activities of a single person. However there is an opportunity to utilize the sensing capabilities of wristbands to offer activity tracking services within the domain of team-based sports games. In this paper we demonstrate the design of an activity tracking system capable of detecting the players’ activities within a one-to-one basketball game. Relying on the inertial sensors of wristbands and smartphones, the system can capture the shooting attempts of each player and provide statistics about their performance. The system is based on a two- level classification architecture, combining data from both players in the game. We employ a technique for semi-automatic labelling of the ground truth that requires minimum manual input during a training game. Using a single game as a training dataset, and applying the classifier on future games we demonstrate that the system can achieve a good level of accuracy detecting the shooting attempts of both players in the game (precision 91.34%, recall 94.31%).
  • Nawaz, S., Efstratiou, C. and Mascolo, C. (2013). ParkSense: A Smartphone Based Sensing System For On-Street Parking. In: Proceedings of the 19th ACM International Conference on Mobile Computing and Networking (MOBICOM 2013).
    Studies of automotive traffic have shown that on average 30% of traffic in congested urban areas is due to cruising drivers looking for parking. While we have witnessed a push towards sensing technologies to monitor real-time parking availability, instrumenting on-street parking throughout a city is a considerable investment. In this paper, we present ParkSense, a smartphone based sensing system that detects if a driver has vacated a parking spot. ParkSense leverages the ubiquitous Wi-Fi beacons in urban areas for sensing unparking events. It utilizes a robust Wi-Fi signature matching approach to detect driver’s return to the parked vehicle. Moreover, it uses a novel approach based on the rate of change of Wi-Fi beacons to sense if the user has started driving. We show that the rate of change of the observed beacons is highly correlated with actual user speed and is a good indicator of whether a user is in a vehicle. Through empirical evaluation, we demonstrate that our approach has a significantly smaller energy footprint than traditional location sensors like GPS and Wi-Fi based positioning while still maintaining sufficient accuracy.
  • Rachuri, K., Efstratiou, C., Leontiadis, I., Mascolo, C. and Rentfrow, P. (2013). METIS: Exploring mobile phone sensing offloading for efficiently supporting social sensing applications. In: Proceedings of the IEEE International Conference on Pervasive Computing and Communications (PERCOM 2013).
  • Efstratiou, C., Leontiadis, I., Picone, M., Rachuri, K., Mascolo, C. and Crowcroft, J. (2012). Sense and Sensibility in a Pervasive World. In: Proceedings of 10th International Conference on Pervasive Computing (PERVASIVE 2012).
    The increasing popularity of location based social services such as Facebook Places, Foursquare and Google Latitude, solicits a new trend in fusing social networking with real world sensing. The availability of a wide range of sensing technologies in our everyday environment presents an opportunity to further enrich social networking systems with ?ne-grained real-world sensing. However, the introduction of passive sensing into a social networking application disrupts the traditional, user-initiated input to social services, raising both privacy and acceptability concerns. In this work we present an empirical study of the introduction of a sensor-driven social sharing application within the working environment of a research institution. Our study is based on a real deployment of a system that involves location tracking, conversation monitoring, and interaction with physical objects. By utilizing surveys, interviews and experience sampling techniques, we report on our ?ndings regarding privacy and user experience issues, and signi?cant factors that can affect acceptability of such services by the users. Our results suggest that such systems deliver signi?cant value in the form of self re?ection and comparison with others, while privacy concerns are raised primarily by the limited control over the way individuals are projected to their peers.
  • Clinch, S., Davies, N., Friday, A. and Efstratiou, C. (2011). Reflections on the long-term use of an experimental digital signage system. In: 13th ACM International Conference on Ubiquitous Computing (UBICOMP 2011). ACM New York, pp. 133-142. Available at: http://dx.doi.org/10.1145/2030112.2030132.
    In this paper we reflect on our long-term experiences of developing, deploying and supporting an experimental digital signage system. Existing public display systems almost always feature a single point of control that is responsible for scheduling content for presentation on the network and provide sophisticated mechanisms for controlling play-out timing and relative ordering. Our experiences suggest that such complex feature-sets are unnecessary in many cases and may be counter productive in signage systems. We describe an alternative, simpler paradigm for encouraging widespread use of signage systems based on shared 'content channels' between content providers and display owners. Our system has been in continuous use for approximately 3 years. We reflect and draw lessons from how our user community has adopted and used the resulting public display network. We believe that these reflections will be of benefit to future developers of ubiquitous display networks.
  • Efstratiou, C. (2010). Challenges in Supporting Federation of Sensor Networks. In: NSF/FIRE Workshop on Federating Computing Resources. NSF. Available at: http://svn.planet-lab.org/wiki/FederationWorkshop.
    Wireless sensor networks are more and more seen as a solution to large-scale tracking and monitoring applications. However, existing networks are designed to serve a single application and deliver information to one authority; typically the owner of the network. This approach is clearly inefficient considering the high cost of deploying a sensor network. Supporting federation of sensor networks can allow the development of new applications that can access recourses offered by multiple existing sensor networks. This paper discusses the challenges in designing a platform for federated sensor networks.
  • Davies, N., Efstratiou, C., Finney, J., Hooper, R., Kortuem, G., Lowton, M. and Strohbach, M. (2006). Health and Safety Compliance in the Field. In: MobiSys2006, 4th International Conference on Mobile Systems, Applications and Services.
  • Davies, N., Cheverst, K., Efstratiou, C. and Friday, A. (2001). The Rational for Infrastructure Support for Adaptive and Context-Aware Applications: A Position Paper. In: NSF Workshop on Infrastructure for Mobile and Wireless Systems. Springer, pp. 146-152.
    Research has demonstrated that mobile and wireless applications benefit from a knowledge of their operating environment. Examples of contextaware or adaptive applications have been constructed and evaluated with the results being widely disseminated within the research community. However, the field is still sufficiently new that there are currently no standards for describing, disseminating or managing the necessary contextual information. Moreover, there are no standards (or even accepted best practices) for coordinating adaptation across multiple applications and systems. In this position paper we argue that the lack of standards in this area will inhibit the widespread deployment of many of the compelling context-aware mobile applications currently being designed.
  • Blair, L., Blair, G., Pang, J. and Efstratiou, C. (2001). `Feature’ Interactions outside a Telecom Domain. In: Workshop on Feature Interactions in Composed Systems, ECOOP2001. Deventer, The Netherlands: Kluwer, B.V., pp. 233-248.
    Feature interactions in the original sense of the term (i.e. within a telecommunications domain), have now been the subject of significant research activity for over ten years. This paper considers several different sources of interactions in other domains, arising during the course of our research at Lancaster. These interactions are taken from a variety of areas within the field of Distributed Systems, and stand to benefit greatly from the application of techniques developed in the feature interaction community. Furthermore, we believe they represent a potentially important generalisation for feature interaction research.
  • Cheverst, K., Efstratiou, C., Davies, N. and Friday, A. (2000). Architectural Ideas for the Support of Adaptive Context-Aware Applications. In: Proceedings of Workshop on Infrastructure for Smart Devices - How to Make Ubiquity an Actuality, HUC’00.
  • Efstratiou, C., Cheverst, K., Davies, N. and Friday, A. (2000). Architectural Requirements for the Effective Support of Adaptive Mobile Applications. In: Work in Progress Paper in Middleware2000. Middleware: Elsevier, pp. 15-26.
    Mobile applications are required to operate in environments that change. Specifically, the availability of resources and services may change significantly during typical system operation. As a consequence, mobile applications need to be capable of adapting to these changes to ensure they offer the best possible level of service to the user. Our experiences of developing adaptive applications have led us to believe that existing middleware fails to provide the necessary support for such applications. Moreover, we believe that current research in this area is also failing to address the core requirements of adaptive mobile systems. In this paper we present a set of requirements for future mobile middleware which have been derived by considering the shortcomings of existing approaches and the needs of application developers. Key among these requirements is the need to support coordinated action between application and system components and the resolution of conflicts caused by the need to adapt to multiple contextual triggers. The paper concludes with the presentation of an architectural framework within which middleware researchers can deploy solutions to the problems identified.
  • Cheverst, K., Davies, N., Mitchell, K., Friday, A. and Efstratiou, C. (2000). Developing a context-aware electronic tourist guide. In: Proceedings of the SIGCHI Conference on Human Factors in Computing Systems. pp. 17-24. Available at: http://dx.doi.org/10.1145/332040.332047.
    In this paper, we describe our experiences of developing and evaluating GUIDE, an intelligent electronic tourist guide. The GUIDE system has been built to overcome many of the limitations of the traditional information and navigation tools available to city visitors. For example, group-based tours are inherently inflexible with fixed starting times and fixed durations and (like most guidebooks) are constrained by the need to satisfy the interests of the majority rather than the specific interests of individuals. Following a period of requirements capture, involving experts in the field of tourism, we developed and installed a system for use by visitors to Lancaster. The system combines mobile computing technologies with a wireless infrastructure to present city visitors with information tailored to both their personal and environmental contexts. In this paper we present an evaluation of GUIDE, focusing on the quality of the visitor's experience when using the system.
  • Efstratiou, C. and Cheverst, K. (2000). Reflection: A Solution For Highly Adaptive Mobile Systems. In: Workshop on Reflective Middleware.

Edited book

  • Efstratiou, C. (2008). Constructing Ambient Intelligence. Gerhäuser, H., Hupp, J., Efstratiou, C. and Heppner, J. eds. Springer Berlin Heidelberg.


  • Raverdy, P., Davies, N., Storz, O. and Efstratiou, C. (2009). System and method for effectively providing user information from a user device. [Online]. Available at: https://doi.org/US patent 7493368.
    A system and method for effectively providing user information from a user device includes an event server that provides restricted access to various types of event content information and services related to a particular event or user community. A wireless portable user device may provide an access code to the event server at a particular event location through a wireless base station that is coupled to a local area network. A system user may thereby utilize the user device to access the event server for downloading appropriate event content information and related community services. The user device may provide one or more different types of profiles and other user feedback to the event server to thereby enable the event server to effectively associate the user device with appropriate event content or other types of related community services.
  • Raverdy, P., Davies, N., Storz, O. and Efstratiou, C. (2005). System and method for selectively providing information to a user device. [Online]. Available at: https://doi.org/US Petent 6957217.
    A system and method for selectively providing information to a user device includes an event server that provides restricted access to various types of event content information and services related to a particular event. A wireless portable user device may provide an access code to the event server at a particular event location through a wireless base station that is coupled to a local area network. A system user may thereby utilize the user device to access the event server for downloading appropriate event content information and related services until the foregoing access code expires.
  • Raverdy, P., Davies, N., Storz, O. and Efstratiou, C. (2005). System and method to support gaming in an electronic network. [Online]. Available at: https://doi.org/US Patent 6884162.
    A system and method to support electronic gaming in an electronic network includes an event server that provides restricted access to various types of game services. One or more system users may utilize corresponding wireless portable user devices for connecting to the event server to thereby gain access to the foregoing game services as game participants. The system users may thereby utilize the user devices to access the event server for accessing appropriate gaming services and related information. In addition, a source system user may utilize a source user device to perform a transfer procedure for transferring ownership rights of an electronic certificate related to the electronic gaming to a target system user through a target user device. The foregoing transfer procedure may be conducted through the event server, or may occur directly from the source user device to the target user device.
  • Raverdy, P., Davies, N., Storz, O. and Efstratiou, C. (2001). System and method for streaming video information to a user device. [Online]. Available at: https://doi.org/US Patent Application 20020069419.
    A system and method for streaming video information to a user device includes an event server that provides restricted access to various types of event content information and services related to a particular event. A wireless portable user device may provide an access code to the event server at a particular event location through a wireless base station that is coupled to a local area network. A system user may thereby utilize the user device to access the event server for downloading appropriate event content information and related services. The event content information may include a direct broadcast of streaming video produced by a video service provider from local video cameras positioned at the particular event. In addition, the event content information may include a plurality of event broadcasts that may be generated by the event server after receiving and storing program information from the local video cameras, the Internet, and various external program sources. The system user may also request individual video-on-demand services for downloading specific requested information from the event server.


  • Efstratiou, C. (2004). Coordinated Adaptation for Adaptive Context-Aware Applications.
    The ability to adapt to change is critical to both mobile and context-aware applications.
    This thesis argues that providing suf?cient support for adaptive context-aware applications
    requires support for coordinated adaptation. Speci?cally, the main argument
    of this thesis is that coordinated adaptation requires applications to delegate adaptation
    control to an entity that can receive state information from multiple applications and
    trigger adaptation in multiple applications. Furthermore, coordination requires support
    for recon?guration of the adaptive behaviour and user involvement. Failure to support
    coordinated adaptation is shown to lead to poor system and application performance and
    insuf?cient support for user requirements.
    An investigation of the existing state-of-the-art in the areas of adaptive and contextaware
    systems and an analysis of the limitations of existing systems leads to the establishment
    of a set of design requirements for the support of coordinated adaptation.
    Speci?cally, adaptation control should be decoupled from the mechanisms implementing
    the adaptive behaviour of the applications, applications should externalise both state
    information and the adaptive mechanisms they support and the adaptation control mechanism
    should allow modi?cations without the need for re-implementation of either the
    application or the support platform.
    This thesis presents the design of a platform derived from the aforementioned requirements.
    This platform utilises a policy based mechanism for controlling adaptation.
    Based on the particular requirements of adaptive context-aware applications a new policy
    language is de?ned derived from Kowalsky's Event Calculus logic programming
    formalism. This policy language allows the speci?cation of policy rules where conditions
    are de?ned through the expression of temporal relationships between events and
    entities that represent duration (i.e. ?uents). A prototype implementation of this design
    allowed the evaluation of the features offered by this platform. This evaluation reveals
    that the platform can support coordinated adaptation with acceptable performance cost.
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