Interruptions have a profound impact on our attentional orientation in everyday life. Recent advances in mobile information technology increase the number of potentially disruptive notifications on mobile devices by an increasing availability of services. Understanding the contextual intricacies that make us receptive to these interruptions is paramount to devising technology that supports interruption management. This thesis makes a number of contributions to the methodology of studying mobile experiences in situ, understanding receptivity to interruptions, and designing context-sensitive systems. This thesis presents a series of real-world studies that investigate opportune moments for interruptions in mobile settings. In order to facilitate the study of the multi-faceted ways opportune moments surface from participants' involvement in the world this thesis develops: - a model of the contextual factors that interact to guide receptivity to interruptions, and - an adaptation of the Experience-Sampling Method (ESM) to capture behavioural response to interruptions in situ. In two naturalistic experiments, participants' experiences of being interrupted on a mobile phone are sampled as they go about their everyday lives. In a field study, participants' experiences are observed and recorded as they use a notification-driven mobile application to create photo-stories in a theme park. Experiment 1 explores the effects of content and time of delivery of the interruption. The results show that receptivity to text messages is significantly affected by message content, while scheduling one's own interruption times in advance does not improve receptivity over randomly timed interruptions. Experiment 2 investigates the hypothesis that opportune moments to deliver notifications are located at the endings of episodes of mobile interaction such as texting and calling. This notification strategy is supported by significant effects in behavioural measures of receptivity, while self-reports and interviews reveal complexities in the subjective experience of the interruption. By employing a mixed methods approach of interviews, observations and an analysis of system logs in the field study, it is shown that participants appreciated location-based notifications as prompts to foreground the application during relative 'downtimes' from other activities. However, an unexpected quantity of redundant notifications meant that visitors soon habituated to and eventually ignored them, which suggests careful, sparing use of notifications in interactive experiences. Overall, the studies showed that contextual mediation of the timing of interruptions (e.g. by phone activity in Experiment 2 and opportune places in the field study) is more likely to lead to interruptions at opportune moments than when participants schedule their own interruptions. However, momentary receptivity and responsiveness to an interruption is determined by the complex and situated interactions of local and relational contextual factors. These contextual factors are captured in a model of receptivity that underlies the interruption process. The studies highlight implications for the design of systems that seek to manage interruptions by adapting the timing of interruptions to the user's situation. In particular, applications to manage interruptions in personal communication and pervasive experiences are considered.

A multilevel modulation format, namely absolute added correlative coding (AACC) is proposed to overcome the effect of fibre dispersion. A novel modulation and demodulation systems are proposed along with bit-error rate (BER) estimation technique. Transmission properties and system applications are also discussed. The research topics are categorised according to the type of the proposed multilevel signalling. It is worth mentioning that AACC can also be implemented with both NRZ and RZ pulse coding based upon the applications in order to optimise their performance.

Magnetic Resonance Imaging (MRI) is a medical imaging technique which is especially sensitive to different soft tissues, producing a good contrast between them. It allows for in vivo visualisation of internal structures in detail and became an indispensable tool in diagnosing and monitoring the brain related diseases and pathologies. Amongst others, MRI can be used to measure random incoherent motion of water molecules, which in turn allows to infer structural information. One of the main challenges in processing and analysing four dimensional diffusion MRI images is low signal quality. To improve the signal quality, either denoising algorithm or angular and spatial regularisations are utilised. Regularisation method based on Laplace--Beltrami smoothing operator was successfully applied to diffusion signal. In this thesis, a new regularisation strength selection scheme for diffusion signal regularisation is introduced. A mathematical model of diffusion signal is used in Monte--Carlo simulations, and a regularisation strength that optimally reconstructs the diffusion signal is sought. The regularisation values found in this research show a different trend than the currently used L-curve analysis, and further improve reconstruction accuracy. Additionally, as an alternative to regularisation methods a backward elimination regression for spherical harmonics is proposed. Instead of using the regularisation term as a low-pass filter, the statistical t-test is classifying regression terms into reliable and corrupted. Four algorithms that use this information are further introduced. As the result, a selective filtering is constructed that retains the angular sharpness of the signal, while at the same time reducing corruptive effect of measurement noise. Finally, a statistical approach for estimating diffusion signal is investigated. Based on the physical properties of water diffusion a prior knowledge for the diffusion signal is constructed. The spherical harmonic transform is then formulated as a Bayesian regression problem. Diffusion signal reconstructed with the addition of such prior knowledge is accurate, noise resilient, and of high quality.

Advances in mobile computing technology and software applications have led to an expansion in potential uses for handheld computers for various tasks. One strong application area is in maintenance and inspection. Network Rail has been progressively developing and applying handheld computers to field-based maintenance and inspection operations, with the aims of improving work productivity and quality, and personal and system safety. However, it is clear that these aims so far have been achieved with varying degrees of success. Handheld computer devices have the potential to enhance the procedure of performing the tasks in many different ways. However, the current handheld computers introduced to maintenance and inspection tasks in Network Rail have principally been designed as data entry tools and in most cases the primary objective is to reduce the amount of paper work and the associated costs and errors. This highlights the need for fundamental research into the ways in which handheld computer technologies should be specified, designed and implemented for effective use in a complex distributed environment such as the rail industry. The main purpose of this research was to study the applications of handheld computers in the rail industry and to generate a set of design principles for development of future systems within Network Rail. The findings of this research have contributed to the identification of human factors principles that need to be considered for design and implementation of successful handheld computer applications. A framework was also developed to summarise and organise information and functional requirements of maintenance workers. Investigating maintenance workers’ requirements through interviews and observations emphasised the importance of rail specific spatial information and the benefits of providing this knowledge to maintenance workers through a mobile computing device which is portable and easy to use. However, displaying rail specific spatial information on the small screen of a handheld computer introduces various HCI issues and challenges. These were addressed in part through a programme of experiments, and therefore the final section of this research focused on examining fundamental aspects of presenting rail specific spatial information on handheld computer screens. The main findings from different stages of this research have been collated into a set of recommendations for design and development of usable and useful applications for handheld computer devices in the rail industry.

A mobile group blog is an example of a Web 2.0 social space, as well as a tool for the instant collection of contextual information, the immediate sharing of information and later reflection. Records in the form of multimedia created through mobile blogging can assist people to keep a versatile representation of artefacts they encounter on the move in everyday life. Overseas students are an example of a large group of people whose cultural learning could be supported by this technology. They could share contextual information and their own stories with other people currently experiencing the host culture, as well as people who do not have the opportunity to experience the host culture first-hand. To examine and evaluate how the mobile group blog could be applied in learning, a case study was conducted on involving overseas students. This research explored the suitability, appropriateness and benefits of a mobile group blog in assisting overseas students to manage their culture shock. It illustrates how the mobility of mobile devices assists the capture of contextual information on the move when overseas students start adapting to the new environment. The group blog site provided a platform to share and exchange their experiences and thoughts, as well as a resource of information on authentic cultural transition for future students. Four sub-studies were conducted around this theme. The first two studies investigated the demands and needs of a mobile group blog application in cultural transition. The third study investigated real and practical mobile blogging activities with a group of twelve Chinese overseas students who had newly arrived in Nottingham. The fourth study was conducted in China. In this study, a number of Chinese students who intended to study abroad were asked to evaluate the contents of the mobile group blog created by the twelve Chinese mobloggers in Study three. Findings from the four studies reveal the possibilities, suitability, strengths and weaknesses of the mobile group blog in assisting cultural transition. The thesis also presents positive feedback from participants as well as feedback on the limitations of this application. Then as added value to this research, it also suggests future educational applications of the mobile group blog.

This thesis investigates terrestrial atmospheric FSO communication systems operating under the influence of turbulence-induced scintillation, beam spreading, optical interchannel crosstalk, amplified spontaneous emission noise and pointing errors. On-off keying-non–return-to-zero (OOK-NRZ) and digital pulse position (DPPM) are the modulation schemes used for the calculations. The possibility of using sophisticated performance evaluation techniques such as moment generating function (MGF)-based Chernoff bound (CB), modified Chernoff bound (MCB) and saddlepoint approximation (SPA) for terrestrial DPPM and OOK-NRZ–based FSO communication systems employing optical amplification are investigated and compared with the conventional Gaussian approximation (GA) method. Relative to the other techniques, the MCB can be considered a safe estimation method for practical systems since it provides an upper bound upon the BER. The turbulent optically preamplified DPPM FSO receiver employing integration over a time slot and comparing the results to choose the largest slot, is seen to give better advantage (about 7 - 9 dB) compared to an equivalent employing OOK-NRZ signalling. The atmospheric turbulence-induced spreading of the beam, ASE noise, and pointing error are seen to combine in a problematic way resulting in high BERs, depending on the size of the receiver and the beam’s jitter standard deviation. Using FSO communication for the distribution links of a passive optical network-like wavelength division multiplexing access network is investigated in the presence of atmospheric turbulence, ASE noise and interchannel crosstalk. The results show that, for clear atmosphere, FSO distribution link length up to 2000 m can be reliably used (depending on turbulence strength) to achieve human eye safety and high capacity access networks. Also, error floors occur due to turbulence accentuated crosstalk effect for the cases of (i) signal turbulent, but crosstalk not and (ii) crosstalk turbulent, but signal not.

This thesis develops efficient tools for modelling wireless communications within highly resonant environments. The aim of these tools is to augment analysis of wireless systems inside closed metallic cavity environments. The primary application for these systems is within the aerospace industry where weight and space are restricted and robustness is critical. The use of ever-advancing wireless communication options would offer significant weight and cost savings and increase safety through supplementing or the replacement of wired systems. The use of a low power wireless system offers the greatest advantage in terms of flexibility and weight. Accordingly, the most suitable applications of the wireless systems are discussed in terms of existing avionic systems. The electromagnetic properties of the aircraft environment and parameters to characterise both the properties of the environment and the wireless signal are introduced. Efficient models are then developed, which characterise the resonant and associated multipath nature of the cavity based on an equivalent circuit approach. The efficiency of these models permits the use of a statistical modelling approach, akin to reverberation chamber measurement techniques, in order to generalise the results for typically non-constant modal structures. Finally, a fractional boundary placement model is developed to augment the transmission line modelling method and permit boundary placement at non-integer positions within a structured mesh. The technique provides a semi-conformal capability with no deleterious impact on the modelling time step. This is then extended to a dynamic model for modelling structural variations during the simulation. A subset of wireless communication approaches is presented and the effectiveness and suitability of such systems are discussed. The developed models are applied to characteristic environments and a selection of the wireless communication methodologies in order to provide examples of their use and an insight into the effect of these environments upon a wireless system.

The increasing popularity of computing devices with short-range wireless offers new communication service opportunities. These devices are small and may be mobile or embedded in almost any type of object imaginable, including cars, tools, appliances, clothing and various consumer goods. The majority of them can store data and transmit it when a wireless, or wired, transmitting medium is available. The mobility of the individuals carrying such short-range wireless devices is important because varying distances creates connection opportunities and disconnections. It is likely that successful forwarding algorithms will be based, at least in part, on the patterns of mobility that are seen in real settings. For this reason, studying human mobility in different environments for extended periods of time is essential. Thus we need to use measurements from realistic settings to drive the development and evaluation of appropriate forwarding algorithms. Recently, several significant efforts have been made to collect data reflecting human mobility. However, these traces are from specific scenarios and their validity is difficult to generalize. In this thesis we contribute to this effort by studying human mobility in shopping malls. We ran a field trial to collect real-world Bluetooth contact data from shop employees and clerks in a shopping mall over six days. This data will allow the informed design of forwarding policies and algorithms for such settings and scenarios, and determine the effects of users' mobility patterns on the prevalence of networking opportunities. Using this data set we have analysed human mobility and interaction patterns in this shopping mall environment. We present evidence of distinct classes of mobility in this situation and characterize them in terms of power law coefficients which approximate inter-contact time distributions. These results are quite different from previous studies in other environments. We have developed a software tool which implements a mobility model for "structured" scenarios such as shopping malls, trade fairs, music festivals, stadiums and museums. In this thesis we define as structured environment, a scenario having definite and highly organised structure, where people are organised by characteristic patterns of relationship and mobility. We analysed the contact traces collected on the field to guide the design of this mobility model. We show that our synthetic mobility model produces inter-contact time and contact duration distributions which approximate well to those of the real traces. Our scenario generator also implements several random mobility models. We compared our Shopping Mall mobility model to three other random mobility models by comparing the performances of two benchmark delay tolerant routing protocols, Epidemic and Prophet, when simulated with movement traces from each model. Thus, we demonstrate that the choice of a mobility model is a significant consideration when designing and evaluating delay-tolerant mobile ad-hoc network protocols. Finally, we have also conducted an initial study to evaluate the effect of delivering messages in shopping mall environments by exclusively forwarding them to customers or sellers, each of which has distinctive mobility patterns.

Location-based Services (LBSs) are important building blocks for a wide spectrum of context-aware applications. The Global Positioning System (GPS) has provided almost ubiquitous positioning services in outdoor environments and enabled many outdoor LBSs such as routing navigation, location check-in and field analysis. However, the indoor LBSs equivalents, e.g., routing the visually-impaired, are not yet pervasively available due to many unaddressed challenges in indoor positioning system deployments. The overarching goal of this project is to develop practical systems to address such challenges and finally build an Open Global Indoor Positioning System (OGIPS). OGIPS is a supplementation to GPS indoors and the combination of OGIPS and GPS is anticipated to provide truly global positioning services to virtually anyone. The Wi-Fi Positioning System (WPS) is a dominant enabling technology of OGIPS for its sheer prevalence in pervasiveness, reliability and performance. This doctoral study project identified three major challenges for building OGIPS based on WPSs and proposed corresponding solutions. The first challenge is how to deploy WPSs with zero cost. WPS deployment requires Radio Map calibration, which, in current industrial practice, relies on high-cost scene analysis. To reduce the deployment cost, it is possible to leverage the free Crowdsourced data. In fact, an enormous amount of Wi-Fi signal measurements could be collected by Implicit Crowdsourcing, that is, collecting unlabeled data in an unobtrusive manner during normal courses of the smartphone users, e.g., strolling around shopping malls. The challenges is then reformulated as how to perform Radio Map calibration via Implicit Crowdsourcing. This project formulates the targeted problem with a novel Hyper-Graph Matching framework, which lends various merits to the system in terms of scalability, extendability and robustness. The elegant problem formulation allows the system to exploit the accomplishments of Graph Matching researches in the past decades, especially in Computer vision. We designed, implemented the system, HyperLoc, and validated it with extensive experiments with both simulated and real-world data. Experimental results indicates that HyperLoc is able to construct zero-cost WPSs in real-world settings. The overall positioning performance of HyperLoc, a zero-cost system, is comparable to high-cost manually-calibrated WPSs . To our knowledge, HyperLoc is the first work to apply Graph Matching techniques to Radio Map calibrations and the first work that develops a practical and scalable zero-cost WPS implementation in real-world settings. The second challenge is how to maintain WPSs performance over time with zero cost. The Radio Map describes the signal environment in relation to the physical environment of a venue. However, the relation often changes substantially upon changes of radio propagation patterns, caused by many factors, e.g., change of the layout of the venue. To maintain consistent and reliable performance, Radio Maps must be versionized and re-calibrated. Here we arrive at the second challenge, that is, how to effectively manage Radio Map versioning with zero cost. This project proposed a novel Radio Map versioning control system, RAEDS, by detecting system anomalous events that degrade indoor positioning performance substantially. The system generalizes arbitrary Radio Map degrading factors as Radio Map anomalous events, which could be modeled and hence detected using state-of-the-art event detection techniques. We designed, implemented and evaluated RAEDS with both synthetic and real-world experiments. The results showed that RAEDS is able to detect anomalous events accurately with a low false alarm rate. To our knowledge, RAEDS is the first work to apply advanced event detection techniques in WPS health monitoring for system versioning control. The combination of HyperLoc and RAEDS is anticipated to enable a practical zero-cost WPS in real-world settings. However, many challenges still present. The OGIPS architecture shall be carefully designed to accommodate the domain-specific requirements of OGIPS in addition to the general requirements of highly-available and scalable systems. Hence the third challenge is how to architect OGIPS to meet the desired requirements. Practical design goals are discussed comprehensively and a proposed design of the architecture and implementations is described in details. Guidelines and recommendations in system implementations were made. More importantly, the proposed OGIPS design is orthogonal to HyperLoc and RAEDS. That means OGIPS is able to flexibly integrate other zero-cost WPSs implementations at high-level. This merit allows other researchers to reuse the proposed architecture with their proprietary zero-cost WPS implementations. The proposed solutions in this work are expected to pave the path towards building OGIPS in real-world settings. Future research efforts will be devoted to improving the adaptiveness and robustness of the proposed systems in terms of device heterogeneity, adaptiveness to user patterns and insufficient data. Finally, the findings of this thesis are expected to contribute to the research communities sharing the same conviction, that is, to make the indoor positioning service accessible to virtually anyone, anytime and anywhere.

This study examines the activity of an online community in developing design creativity. This involved undergraduate Malaysian university students and their tutor from the School of Education, and professional designers in a private online community using the social network site - Facebook - to improve interface design (websites or interactive courseware). Two research processes adapted from different communities - the creative industries and the higher education communities - were applied in the collaboration. Each community embraces distinctive methods, objectives, instruments, rules and roles in producing design. Contradictions and tensions resulting from incorporating these two communities were analysed. In addition, the effect of social interactions on students’ performance, awareness, and perspectives were also investigated. A qualitative approach was utilized and data consisted of online semi-structured questionnaires, face-to-face interviews, field documentation on Facebook, and Facebook chat. The process of analysis is divided into two parts: initial analysis and substantive analysis of four case studies. Thematic (Braun and Clarke, 2006) and comprehensive data treatment (Silverman, 2010) approaches were used to analyse the initial data. Activity systems analysis (Engeström, 1999) was employed in the substantive analysis to explore the contradictions within the collaboration. The results indicate that contradictions occurred due to the new practice introduced by the community of practitioners (the designers). The collision of new practice positioned students in a disequilibrium stage but managed to also improve students’ design outcomes and promote awareness of the importance of producing purposeful design. However it also revealed the importance of both cognitive and emotional support during the process as the harsh nature of the feedback from designers could potentially hinder creativity. The findings of this study contribute to our understanding that the social-cultural process of creativity can be nurtured within higher education through the use of social network sites such as Facebook. It concludes that more research exploring online social interactions between a learning community and a community of practitioners is required in order to better understand the benefits it has to offer for creativity development.