Publications
In Press
Article
Multimedia Systems
This paper presents a RESTful Web service platform for building mixed reality applications for both Web browsers and mobile clients. Having a common service backend makes creating applications fast, simple, and open to 3rd parties. The paper presents two mixed reality applications that have been built on the platform. It summarizes requirements for a mixed reality platform and defines a mixed reality domain model that the platform and applications share. In addition, it describes how the clients can use the REST interface to perform operations on user-generated content, as well as access real life commercial geo-content such as street view panoramas and building models.
Article
Pervasive Computing
Nokia Research Center’s Multimedia Technologies Laboratory in Santa Monica, CA is exploring how to design engaging, entertaining, and exciting novel experiences using interactive pervasive technologies. This exploration is exemplified by their creation of a socially-activated gaming experience built upon a custom platform of a multitude of interactive pervasive technologies. The results of a series of user tests of the game are discussed and techniques for overcoming challenges associated with the design of interactive applications for pervasive platforms are highlighted as potentially generalizable design insights
Article
Personal and Ubiquitous Computing
In this paper, we investigate the relation-
ship between automatically extracted behavioral char-
acteristics derived from rich smartphone data and self-
reported Big-Five personality traits (Extraversion, Agree-
ableness, Conscientiousness, Emotional Stability and
Openness to Experience). Our data stems from smart-
phones of 117 Nokia N95 smartphone users, collected
over a continuous period of 17 months in Switzerland.
From the analysis, we show that several aggregated fea-
tures obtained from smartphone usage data can be in-
dicators of the Big-Five traits. Next, we describe a ma-
chine learning method to detect the personality trait of
a user based on smartphone usage. Finally, we study the
bene ts of using gender-speci c models for this task.
Apart from a psychological viewpoint, this study facil-
itates further research on the automated classi cation
and usage of personality traits for personalizing services
on smartphones.
In Proceedings
ACM Conference of Computer Supported Cooperative Work
ACM
Proceedings
NDSS
2012
Article
ACM Transactions on Intelligent Systems and Technology (ACM-TIST)
With the prevalence of smart mobile devices with multiple sensors, the commercial application of intelligent
context-aware services becomes more and more attractive. However, limited by the battery capacity, the
energy efficiency of context-sensing is the bottleneck for the success of context-aware applications. Though
several previous studies for energy efficient context-sensing have been reported, none of them can be applied
to multiple types of high energy consuming sensors. Moreover, applying machine learning technologies to
energy efficient context-sensing is under-explored too. In this paper, we propose to leverage machine learn-
ing technologies for improving the energy efficiency of multiple high energy consuming context sensors by
trading-off the sensing accuracy. To be specific, we try to infer the status of high energy consuming sen-
sors according to the outputs of software based sensors and the physical sensors that are necessary to work
all the time for supporting the basic functions of mobile devices. If the inference indicates the high energy
consuming sensor is in a stable status, we avoid the unnecessary invocation and instead use the latest in-
voked value as the estimation. The experimental results on real data sets show that the energy efficiency of
GPS sensing and audio level sensing are significantly improved by the proposed approach while the sensing
accuracy is over 90%.
In Book
Handbook of Visual Display Technology
The transmissive and transflective LCDs are essentially stacks of optical films. Aside from the electro-optic function of the LC material itself, the viewing characteristics of the display are determined by the optical properties of these films. This chapter concentrates on the light management in mobile LCDs starting with light sources and light guide plates, and subsequently the role of individual film layers in light management is described.
Article
Special Issue of the Elsevier’s Journal of Systems and Software on “Mobile Applications: Status and Trends”
Mobile devices are increasingly being used to store and manage users' personal information, as well as to access popular third-party context-based services. Very often, these applications need to determine common availabilities among a set of user schedules, in order to allow colleagues, business partners and people to meet. The privacy of the scheduling operation is paramount to the success of such applications, as often users do not want to share their personal schedule details with other users or third-parties. In this paper, we propose practical and privacy-preserving solutions for mobile devices to the server-based scheduling problem. Our three novel algorithms take advantage of the homomorphic properties of well-known cryptosystems in order to privately and efficiently compute common user availabilities. We also formally outline the privacy requirements in such scheduling applications and we implement our solutions on real mobile devices. The experimental measurements and analytical results show that the proposed solutions not only satisfy the privacy properties but also fare better, in regard to computation and communication efficiency, compared to other well-known solutions. Finally, we assess the utility and expectations, in terms of privacy and usability, of the proposed solutions by means of a targeted survey and user-study of mobile-phone users.
Article
Distributed and Parallel Databases
Many applications of wireless sensor networks monitor the physical world and report events of interest. To facilitate event detection in these applications, in this paper we propose a pattern-based event detection approach and integrate the approach into an in-network sensor query processing framework. Different from existing threshold-based event detection, we abstract events into patterns in sensory data and convert the problem of event detection into a pattern matching problem.We focus
on applying single-node temporal patterns, and define the general patterns as well as five types of basic patterns for event specification. Considering the limited storage on sensor nodes, we design an on-node cache manager to maintain the historical data required for pattern matching and develop event-driven processing techniques for queries in our framework. We have conducted experiments using patterns for events that are extracted from real-world datasets. The results demonstrate the effectiveness and efficiency of our approach.
Conference
CSCW
ACM Press
In Northern rural China, many people own a mobile phone without ever having purchased it: they received it as a gift from better off relatives, usually their migrant children. Drawing from ethnographic field work in three Chinese villages, we describe practices of mobile phone gifting and the social relations that underlie them, as well as the consequences of the circulation of mobile phones, from the change of use that happens when they move from an urban environment to the countryside, to the possibilities that they open up or close out for rural users. We conclude with implications for technology design that emphasize the situated nature of these experiences and thoughtful approaches to the design of ‘traveling’ mobiles.
Conference
CSCW2012
Group buying is a business model where people with the same merchandize interests form a group and conduct the purchase together to achieve a discount. Third-party proxy websites negotiate with merchants for appealing deals and then provide them to end customers. We call it online group buying. Besides, there exists local group buying where the joiners, the initiator, and sometimes even the merchants are in the same local community. Such locality induces some interesting characteristics in group buying, which remain largely unexplored in the research community. This study attempts to reveal users’ behaviors in group buying within the local context. We developed a mobile service called “HappyGo” that supports local group buying. We conducted a trial involving more than 300 users from a company office. From our findings, we believe that local group buying complements online group buying by creating a “local” economic circle while also providing users with social benefits.
In Book
Handbook of Visual Display Technology
Springer-SBM
Energy savings and device efficiency aspects have become increasingly important in mobile device design. Displays are responsible for a large portion of modern mobile multimedia device power consumption, and thus, traditional power management methods often rely on shutting off the display for inactive periods. Since the multimedia consumption is becoming the prominent use case for a mobile device, this logic does not apply for power savings any more. The focus needs to shift to making the device itself more power-efficient. This Chapter describes some of the power management principles for modern mobile multimedia displays.
In Book
Handbook of Visual Display Technology
Springer-SBM
Displays can be found in many handheld electronic products, especially those that rely on visual communication and multimedia. These are features that ever more often also appear among the variety that today’s mobile phones offer. The mobile phone market can be thought of as the model market of display-centric handheld electronic devices. This Chapter describes shortly the history of the display in a mobile phone, discusses the mobile display requirements, and summarizes the technology alternatives for mobile device displays. Finally, a short outline of the Section is given.
In Book
Handbook of Visual Display Technology
Springer-SBM
Besides transmissive and transflective displays, especially organic light-emitting devices (OLEDs) are present on the mobile display market. Of these, mobile display aspects of OLEDs are introduced in this Chapter. In addition to these main display technologies, there are many others that attempt to gain a presence on the mobile device application area. Some of these, such as Field Sequential Color (FSC) displays, Electrowetting Displays (EWDs), Micro-ElectroMechanical (MEMS) displays, and Autostereoscopic Displays are discussed. Finally, as a special case, Electrophoretic Displays (EPIDs) are described, as applied to Electronic Book Reader (EBR) displays.
In Book
Handbook of Visual Display Technology
Springer-SBM
An introduction to transflective displays for mobile devices is given, and the transflective display structure is discussed, with regard to optimization of the display to mobile devices. Ways to improve the viewing angle of transflective displays are described. Finally, some aspects of integrating touch capability to transflective displays are given.
Article
Electronics Letters
In Proceedings
CHI
ACM Press
Proceedings
PAKDD 2012: The 16th Pacific-Asia Conference on Knowledge Discovery and Data Mining
2011
Article
IEEE Transactions on Information Forensics and Security
“Pairing” is the establishment of authenticated key agreement between two devices over a wireless channel. Such devices are ad hoc in nature as they lack any common preshared secrets or trusted authority. Fortunately, these devices can be connected via auxiliary physical (audio, visual, tactile) channels which can be authenticated by human users. They can, therefore, be used to form the basis of a pairing operation. Recently proposed pairing protocols and methods are based upon bidirectional physical channels. However, various pairing scenarios are asymmetric in nature, i.e., only a unidirectional physical channel exists between two devices (such as between a cell phone and an access point). In this paper, we show how strong mutual authentication can be achieved even with a unidirectional visual channel, where prior methods could provide only a weaker property termed as presence. This could help reduce the execution time and improve usability of prior pairing methods. In addition, by adopting recently proposed improved pairing protocols, we propose how visual channel authentication can be used even on devices that have very limited displaying capabilities, all the way down to a device whose display consists of a cheap single light-source, such as a light-emitting diode. We present the results of a preliminary usability study evaluating our proposed method.
Conference
Printed electronics Europe 2011
IDtechEX
· Overview of stretchable electronics.
· Applications in mobile devices.
· Current research at Nokia.
Conference
MobileHCI
Workshop website: http://familyinteraction.wordpress.com
Recent studies have demonstrated that children’s use of mobile devices has rapidly increased, especially with smartphones, i.e. devices that are capable to connect to the Internet. This has lead to increase interest from regulators and policy makers in the field to understand the nature of opportunities and potential threats of these new mobile forms of communication. However, what has been indicated in many reports is that the research conducted regarding these matters is parse, needing attention from several fields.
This workshop focuses on the use of mobile communication by and among children (6-12 years), and within families. We invite empirical studies of the usage, threats and opportunities of mobile computing with children. We also invite theoretical works and more practice-orientated case studies about improving media literacy skills, child-child mediation as a method for cooping with the risks and other related topics. The focus should be on how the parent-child mediation is affected by ongoing technological changes in our society, and moreover how the mobile interaction can be used to improve family life.
Conference
the 13th international conferenceProceedings of the 13th international conference on Ubiquitous computing - UbiComp '11
ACM Press
With the rising popularity of social networks, people’s
locations are being used for providing rich mobile social
services. We present a mobile social service in our office
environment called Find & Connect. We use WiFi to record a
user’s position and allow users to efficiently find, reserve and
manage office resources, like meeting rooms and desks, and
easily connect to other colleagues through scheduled
interactions like having a meeting and/or unscheduled yet
implicit interactions like ephemeral encounters. We then
describe how we manage office resources and connect with
people, followed by a user study that we conducted in our
office.
Conference
ACM SIG CHI 2011 (Video interaction)
ACM
With the rapid adoption of smart phones and the improvement of multimedia techniques in recent years, video-taking has become an important method of logging personal life. However, state of the art mobile video summarization techniques are generally unable to record and analyze videos simultaneously. We propose MoViShooter (Mobile Video Shooter), a novel application that can automatically extract key frames and create bookmarks accordingly during the mobile video recording. It also provides users the ability to create customized bookmarks on the fly. MoViShooter
greatly improves user experience by two means, 1) it provides instant feedback to users during the video recording; 2) it provides much fast and easier navigation for later video playback.Evaluation results demonstrate that our approach improves both efficiency and usability significantly.
Conference
the 13th International Conference on Advanced Communication Technology (ICACT2011)
With the fast development of mobile devices and wireless technology, more and more mobile devices are equipped with multiple network interfaces. Particularly, due to its high throughput and low cost, Wi-Fi is becoming one of the most popular interfaces. However, the high power consumption hinders its daily use in mobile devices to some extent. To tackle this problem, we present a Zigbee based Collaborative AP Discovery scheme (ZCAD) in this paper. ZCAD empowers mobile devices to share the ambient AP (Access Point) information (e.g., SSID, signal strength) via Zigbee interfaces,
which enables mobile devices to directly associate with the available APs without first scanning them. Extensive experimental results demonstrate that ZCAD can significantly decrease the number of scanning for AP discovery and therefore effectively reduce the power consumption of Wi-Fi communications.
Proceedings
8th International Conference on Mobile Web Information Systems
Elsevier Science
With more and more personal data being collected and stored by service providers, there is an increasing need to
ensure that their usage is compliant with privacy regulations and user preferences. We consider the specific scenario where promised usage is specified as metric temporal logic policies, and these policies can be verified against the database usage logs. Given the vast amount of data being collected, scalability is very important. In this work, we show how such usage monitoring can be performed in a distributed fashion for an expressive set of policies. Experimental results are given for a real-life use case to show the genericness and scalability of the results.
Proceedings
13th IEEE International High Assurance Systems Engineering Symposium
IEEE CS
With more and more personal data being collected and stored by service providers, there is an increasing
need to ensure that their usage is compliant with privacy regulations. We consider the specific scenario where
policies are defined in metric temporal logic and audited against the database usage logs. Previous works have
shown that this can indeed be achieved in an efficient manner for a very expressive set of policies. One of the
main ingredients of such an auditing process is clearly the availability of sufficient database logs. Currently, it is a manual process to first determine the logs needed, and then come up with the necessary auditing specifications to generate them. This is not only a time consuming process, but can be erroneous as well leading to either insufficient or redundant logging. Logging in general is costly as it is an overhead on the real-time database performance, and hence redundant logging is not an option either.
Our main contribution in this work is to streamline the log generation process by deriving the auditing specifications directly from the given privacy policies. We also show how the required logging can be minimized based on the temporal constraints in the policies. Given privacy policies as input, the output of the proposed tool is the corresponding auditing specifications that can be installed directly in the databases; to produce logs that are both minimal and sufficient to audit the given policies. The tool has been implemented and tested in a real-life scenario.
Proceedings
The 4th International Conference on Human-Centric Computing
Springer
With mobile devices and wireless technology becoming pervasive at conferences, conference attendees can use location-based mobile social networking applications such as Foursquare and Gowalla to share their location and content with others. How to use the mobile devices and the indoor positioning technology to help the conference participants enhance the real-world interactions of people and improve efficiency during the conference? In this paper, we report our work in Nokia Find & Connect (NF&C) to solve this problem where we use location and encounters, together with the conference basic services, all through a mobile UI. To demonstrate the usefulness of the NF&C system, we conducted a field trial at the 7th International Conference on Ubiquitous Intelligence and Computing and Autonomic and Trusted Computing (UIC/ATC 2010). Results show that NF&C can help the conference participants enhance the real-world interactions of people and improve efficiency at a conference effectively.
In Proceedings
The Third International Conference on Communication Systems and Networks (COMSNETS)
Wireless Multi-Hop CSMA/CA Networks are chal- lenging to analyze. On the one hand, their dynamics are complex and rather subtle effects may severely affect their performance. Yet, understanding these effects is critical to operate upper layer protocols, such as TCP/IP. On the other hand, their models tend to be very complex in order to reproduce all the features of the protocol. As a result, they do not convey much insight into the essential features.
We review two models of 802.11 protocols, which are simple enough to first explain why a trade-off needs to be found between fairness and spatial reuse (throughput) in saturated wireless networks (where all nodes have packets to transmit to their neighbors); and then to explain why non-saturated networks (where only some nodes, the sources, have packets to transmit to their destinations in a multi-hop fashion) that are more than 3 hops longs suffer from instability. We confront both models either to realistic simulations in ns-2 or to experiments with a testbed deployed at EPFL. We find that the predictions of both models help us understand the performance of the 802.11 protocol, and provide hints about the changes that need to be brought to the protocol.
Conference
IEEE International Conference on Communications (ICC 2011)
IEEE
Wireless ad hoc networks can experience significant performance degradation under fading channels. In this work, we present a robust forwarding extension (RFE) for reactive routing protocols in wireless ad hoc networks. RFE is designed to enhance existing reactive routing protocols to provide reliable and energy efficient packet delivery against the unreliable wireless links. Specifically, we introduce a biased backoff scheme during the route discovery phase to find a robust virtual path, which can provide more cooperative forwarding opportunities. Along this virtual path, data packets are greedily progressed toward the destination through nodes cooperation. We extend the widely used AODV routing protocol with RFE to study its performance. Through extensive simulations, we demonstrate that AODV-RFE effectively improves the reliability, end-to-end energy efficiency
and latency.
Conference
the 2011 annual conferenceProceedings of the 2011 annual conference on Human factors in computing systems - CHI '11
ACM Press
Whereas communication technology to connect people has long been an integral part of our everyday lives, it has only recently expanded to offer applications for dogs and dog-owners. In this paper, we present two explorative studies to understand the experiences and expectations of dog owners for communication technology to support their interaction with dogs. These studies look at two different user groups, hunters and pet owners, charting the lessons learnt from the current technology and exploring the aspects that should be taken into account when designing future applications and services. Our findings reveal that usability problems are still the dominant issue with current applications. We also suggest key design implications which can be utilized in the development of future human-dog interaction systems.
Conference
International Conference on Innovation and Information Management (ICIIM 2011)
When searching on semantic desktop, current keyword search approaches provide a comfortable way for end users to express their information needs based on keywords, while ontology-based semantic search promises to produce more accurate answers to user queries by taking advantage of the availability of explicit semantics of information. Therefore, how to combine these two search approaches to enable end users find their real information needs efficiently is a problem. In this paper, we present an approach for translating end users’ keyword queries to semantic SPARQL formal queries on semantic desktop effectively, which mainly takes three steps: keywords mapping, formal query construction and query ranking. The experiment shows that our approach achieved encouraging searching results.
Conference
Proc. IEEE International Conference on Image Processing
We tackle the challenge of web image classification using additional tags information. Unlike traditional methods that only use the combination of several low-level features, we try to use semantic concepts to represent images and corresponding tags. At first, we extract the latent topic
information by probabilistic latent semantic analysis (pLSA) algorithm, and then use multi-label multiple kernel learning to combine visual and textual features to make a better image classification. In our experiments on PASCAL VOC’07 set and MIR Flickr set, we demonstrate the benefit of using multimodal feature to improve image classification. Specifically, we discover that on the issue of image classification, utilizing latent semantic feature to represent images and associated tags can obtain better classification results than other ways that integrating several low-level features.
Proceedings
Second annual ACM conference on Multimedia systems (MMSys '11)
ACM, New York, NY, USA
We survey popular data sets used in computer vision literature and point out their limitations for mobile visual search applications. To overcome many of the limitations, we propose the Stanford Mobile Visual Search data set. The data set contains camera-phone images of products, CDs, books, outdoor landmarks, business cards, text documents, museum paintings and video clips. The data set has several key characteristics lacking in existing data sets: rigid objects, widely varying lighting conditions, perspective distortion, foreground and background clutter, realistic ground-truth reference data, and query data collected from heterogeneous low and high-end camera phones. We hope that the data set will help push research forward in the field of mobile visual search.
Article
IEEE Transactions on Mobile Computing
We study the integrated WiFi/WiMAX networks, where users are equipped with dual-radio interfaces that can connect to either a WiFi or a WiMAX network. Previous research on integrated heterogeneous networks (e.g., WiFi/cellular) usually considers one network as the main and the other as the auxiliary. The performance of the integrated network is compared with the "main” network. The gain is apparently due to the additional resources from the auxiliary network. In this study, we are interested in integration gain that comes from the better utilization of the resource rather than the increase of the resource. The heterogeneity of the two networks is the fundamental reason for the integration gain. To quantify it, we design a generic framework that supports different performance objectives. We focus on the max-min throughput fairness in this work and also briefly cover the proportional fairness metric. We first prove that it is NP-hard to achieve integral max-min throughput fairness, then propose a heuristic algorithm, which provides two-approximation to the optimal fractional solution. Simulation results demonstrate significant integration gain from three sources, namely, spatial multiplexing, multinetwork diversity, and multiuser diversity. For the proportional fairness metric, we derive the formulation and propose a heuristic algorithm, which shows satisfactory performance when compared with the optimal solution.
Article
Nanotechnology
We study the high pressure response, up to 8 GPa, of silicon nanowires (SiNWs) with ~15 nm diameter, by Raman spectroscopy. The first order Raman peak shows a superlinear trend, more pronounced compared to bulk Si. Combining transmission electron microscopy and Raman measurements we estimate the SiNWs’ bulk modulus and the Gruneisen parameters. We detect an increase of Raman linewidth at 4 GPa, and assign it to pressure induced activation of a decay process into LO and TA phonons. This pressure is smaller compared to the 7 GPa reported for bulk Si. We do not observe evidence of phase transitions, such as discontinuities or change in the pressure slopes, in the investigated pressure range.
Article
Nano Research
We present temperature and power dependent photoluminescence measurements on CdSe nanowires synthesized via vapor-phase with and without the use of a metal catalyst. Nanowires produced without a catalyst can be optimized to yield higher quantum efficiency, and narrower and spatially uniform emission, when compared to the catalyst-assisted ones. Emission at energies lower than the band-edge is also found in both cases. By combining spatially-resolved photoluminescence and electron microscopy on the same nanowires, we show that catalyst-free nanowires exhibit a low-energy peak with sharp phonon replica, whereas for catalyst-assisted nanowires low-energy emission is linked to the presence of nanostructures with extended morphological defects.
In Proceedings
ACM symposium on User Interface Software and Technology (UIST)
We present RhythmLink, a system that improves the wireless pairing user experience. Users can link devices such as phones and headsets together by tapping a known rhythm on each device. In contrast to current solutions, RhythmLink does not require user interaction with the host device during the pairing process; and it only requires binary input on the peripheral, making it appropriate for small devices with minimal physical affordances. We describe the challenges in enabling this user experience and our solution, an algorithm that allows two devices to compare imprecisely-entered tap sequences while maintaining the secrecy of those sequences. We also discuss our prototype implementation of RhythmLink and review the results of initial user tests.
Article
Wireless Communications and Mobile Computing
We present a system for real-time traffic support in infrastructure and ad hoc IEEE 802.11 networks. The proposed elastic MAC (E-MAC) protocol provides a distributed transmission schedule for stations with real-time traffic requirements, while allowing a seamless coexistence with standard IEEE 802.11 clients, protecting best-effort 802.11 traffic from starvation by means of admission control policies. Our scheduling decisions are based on an ‘elastic’ transmission opportunity (TXOP) assignment which allows for efficient wireless resource usage: whenever a real-time station does not use the assigned TXOP, the other real-time stations can take over the unused access opportunity, thus preventing the well-known inefficiencies of static time division multiple access (TDMA) schemes. Unlike other TDMA-based solutions for 802.11, E-MAC does not require a tight synchronization among the participating clients, thus allowing its implementation on commodity WLAN hardware via minor software changes at the client side, and no changes at the access points (APs). We studied the performance of our mechanism via ns-2 simulations and a mathematical model, showing that it outperforms IEEE 802.11e in terms of throughput, delay, and jitter. We finally provide a proof of concept through the results obtained in a real testbed where we implemented the E-MAC protocol.
Conference
MRS Spring Meeting 2011
We present a robust, thin and optically transparent interface structure that can be overlaid unobtrusively on top of a display screen. This structure acts as an electrotactile system that directly delivers localized and visually correlated tactile information to the user’s skin, enabling graphic tactile feedback. The device structure operates at very low current level (< 10µA) and with potentials in the range of tens of volts, which is a significant improvement on current electrotactile paradigms. The proposed structure doubles as an input and output device in assisting the user interaction with a touch screen display.
The technology is based on electrovibration, in which touch receptors in the skin can be deceived into perceiving texture when a fingertip is swiped across an insulating layer above a metal surface carrying an alternating potential. This effect is due to the varying electrostatic attraction between the conductor and the deeper, liquid-rich conducting layers of the skin – an effect which changes the perceived dynamic friction. Complex stimulation patterns, involving the mixing of multiple AC frequency components (10Hz – 500Hz) and the actuation of several electrodes simultaneously, may allow for the generation of an unprecedented range of “haptic illusions”. These may range from the emulation of real touch sensations, to completely new patterns of tactile feedback, and new ways of interacting with electronic devices. This solution also overcomes the need for the physical displacement of mechanical parts and is therefore several orders-of-magnitude more energetically efficient in providing real time feedback to the user.
Our work tackles the expected evolution of mobile devices and displays towards flexible and compliant form factors. Our concept implementation is based on the use of novel nanomaterials and structures that are compatible with the requirements for these new technologies. Conductors that are simultaneously flexible, conductive and transparent have been investigated, ranging from wide-bandgap oxide materials to carbon nanostructures, e.g., carbon nanotube networks and graphene, and also include silver nanowire networks and thin metal grids. These conductors can all be deposited on flexible substrates, and uniformly coated with appropriate dielectric materials. Much focus has been on high-k amorphous oxide materials such as hafnia, but, barium titanate and parylene have also been used. The exploration of an extensive materials library necessitates use of a number different fabrication techniques including sputtering, vacuum deposition, and various solution methods and printing techniques. In addition, the inclusion of scratch resistant, hydrophobic and oleophobic materials on the top surface to combine electrical insulation, scratch resistance and stain/water/fingerprint repellence in a single finishing layer helps maintain and protect a pristine display surface.
Conference
ICASSP
IEEE
We present a novel approach to represent transients using amplitude-modulated/frequency-modulated (AM-FM) signals. The model is applied to the real and imaginary parts of the Fourier transform (FT) of the transient. The suitability of the model lies in the observation that since transients are well-localized in time, the real and imaginary parts of the Fourier spectrum have a modulation structure. The spectral AM is the envelope and the spectral FM is the group delay function. The group delay is estimated using spectral zero-crossings and the spectral envelope is estimated using a coherent demodulator. We show that the proposed technique is robust in the presence of additive noise. We present applications of the proposed technique to castanets and stop-consonants in speech
Conference
Indoor Positioning and Indoor Navigation
We describe the design, implementation, and evaluation of Mole, a mobile organic localization engine. Unlike previous work on crowd-sourced WiFi positioning, Mole uses a hierarchical name space. By not relying on a map and by being more strict than uninterpreted names for places, Mole aims for a more flexible and scalable point in the design space of localization systems. Mole employs several new techniques, including a new statistical positioning algorithm to differentiate between neighboring places, a motion detector to reduce update lag, and a scalable cloud-based fingerprint distribution system. Mole's localization algorithm, called Maximum Overlap (MAO), accounts for temporal variations in a place's fingerprint in a principled manner. It also allows for aggregation of fingerprints from many users and is compact enough for on-device storage. We show through end-to-end experiments in two deployments that MAO is significantly more accurate than state-of-the-art Bayesian-based localizers. We also show that non-experts can use Mole to quickly survey a building, enabling room-grained location-based services for themselves and others.
Conference
Proceedings of the 10th ACM SIGPLAN workshop on Erlang - Erlang '11
ACM Press
We describe the design and implementation of Disco, a distributed computing platform for MapReduce style computations on large-scale data. Disco is designed for operation in clusters of commodity server machines, and provides both a fault-tolerant scheduling and execution layer as well as a distributed and replicated storage layer. Disco is implemented in Erlang and Python; Erlang is used for the implementation of the core aspects of cluster monitoring, job management, task scheduling and distributed filesystem, while Python is used to implement the standard Disco library.
Disco has been used in production for several years at Nokia, to analyze tens of terabytes of data daily on a cluster of over 100 nodes. With a small but very functional codebase, it provides a free, proven, and effective component of a full-fledged data analytics stack.
Proceedings
2nd ACM International Conference on Performance Engineering
ACM Press
We consider large scale Publish/Subscribe systems deployed across multiple organizations. However, such cross organizational deployment is often hindered by firewalls and Network Address Translators (NATs). Several workarounds have been proposed to allow firewall and NAT traversal, e.g. VPN, connection reversal, relay routers. However, each traversal mechanism in turn leads to trade-offs with respect to implementation complexity, infrastructure overhead, latency, etc. We focus on the latency aspect in this work. We propose a cost-performance model that allows quantitative evaluation of the performance latency induced by the different firewall traversal mechanisms. The utility of the model is that for a given network configuration, it is able to provide a (close) approximation of the performance latencies based on simulation results, without actually having to deploy them in practice. This also allows selecting the best traversal mechanism for a given configuration. Finally, experimental results are given to show the validity of the proposed model.
In Proceedings
IEEE International Symposium on Information Theory
We conduct an experiment where ten attendees of an open-air music festival are acting as Bluetooth probes. We then construct a parametric statistical model to estimate the total number of visible Bluetooth devices in the festival area. By comparing our estimate with ground truth information provided by probes at the entrances of the festival, we show that the total population can be estimated with a surprisingly low error (1.26% in our experiment), given the small number of agents compared to the area of the festival and the fact that they are regular attendees who move randomly. Also, our statistical model can easily be adapted to obtain more detailed estimates, such as the evolution of the population size over time.
In Proceedings
Trust and Trustworthy Computing (TRUST 2011)
Springer
We address property-based attestation in the context of an in-vehicle communication system called Terminal Mode that allows mobile devices to “stream” services, such as navigation or music, to car head-units. In Terminal Mode, attestation of the mobile device is needed to enforce driver distraction regulations and traditional binary attestation is not applicable due to frequently needed measurement updates and limited connectivity of car head-units. We present a novel attestation scheme that bootstraps from existing application certification infrastructures available on mobile device platforms, and thus avoids the need to setup and maintain a new service that provides translation from software measurements to properties, and consequently makes realization of property-based attestation economically feasible.
Article
Journal of the SID
Virtual-image (near-to-eye) and two-view autostereoscopic (3-D) displays share similar optical properties in the comfortable user position for viewing. In this paper, the definitions and criteria
of qualified viewing space (QVS) and qualified stereoscopic viewing space (QSVS) are discussed. Due to the complex nature of these viewing spaces, the related presumptions and the required optical characteristics and their measurements are specified. The effects of different display and observer parameters, such as interpupillary distance, to the resulting viewing spaces are discussed. Finally, real measurement data of two autostereoscopic display devices are presented.
Conference
ACM International Conference on Ubiquitous Computing (UbiComp)
ACM
Users often engage in tasks that span multiple personal devices. Although many current solutions exist to provide ubiquitous access to one’s data, users continue to struggle with cross-device tasks. These solutions often require them to plan ahead for their information needs. In this paper, we present Myngle, a device-agnostic system that lets users quickly find the information they are looking for from previously visited web pages without having to plan ahead. Myngle provides a unified web history from multiple personal devices, and allows users to filter their history based on high-level categories influenced by common mobile information need categories (e.g., address, phone number). We evaluated Myngle with 32 users and found that our category-based method of filtering eases the burden of continuing cross-device tasks.
Conference
3DTV Conference 2011
IEEE
Under many viewing circumstances, asymmetric stereoscopic video coding provides similar perceived quality with significant decrease in bitrate, computational complexity, and memory usage compared to conventional stereoscopic video coding. However, in other circumstances, users may prefer conventional symmetric stereoscopic video to asymmetric stereoscopic video. This paper presents a stereoscopic video coding scheme including asymmetric spatial scalability to provide the bitstream adaptation capability to meet heterogeneous network conditions, receiver devices, and user preferences. The spatial scalability property is enabled for the non-base view, and hence the coded bitstream can be decoded as conventional or mixed-resolution stereoscopic video. Simulation results show that the proposed method outperforms the tested other coding schemes providing the same scalability property by at least 8.2% in terms of average bitrate saving.
