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.
Conference
134th Convention, Audio Engineering Society
Detection of tonal components from magnitude spectrum is an important initial step in several speech and audio processing applications. In this paper we present an approach for detecting sinusoidal components from the magnitude spectrum using “goodness-of-fit” test. The key idea is to test the null-hypothesis that the region of spectrum under observation is drawn from the magnitude spectrum of an ideal windowedsinusoid. This hypothesis is tested with a chi-square “goodness-of-fit” test. The outcome of this hypothesis test is a decision about the presence of sinusoid in the observed region of magnitude spectrum. We have evaluated the performance of proposed approach using synthetically generated samples containing steady and modulated harmonics in clean and noisy conditions.
Article
Data Mining and Knowledge Discovery
<p>We study the extent to which social ties between people can be<br /> inferred in large social network, in particular via active user interactions. In<br /> most online social networks, relationships are lack of meaning labels (e.g.,<br /> “colleague” and “intimate friends”) due to various reasons. Understanding<br /> the formation of different types of social relationships can provide us insights<br /> into the micro-level dynamics of the social network. In this work, we precisely<br /> define the problem of inferring social ties and propose a Partially-Labeled<br /> Pairwise Factor Graph Model (PLP-FGM) for learning to infer the type of<br /> social relationships. The model formalizes the problem of inferring social ties<br /> into a flexible semi-supervised framework. We test the model on three different<br /> genres of data sets and demonstrate that it is possible to accurately infer<br /> 85% of social relationships. We further study how to maximally leverage user<br /> interactions to help improve the learning accuracy. Two active learning based<br /> algorithms are proposed to actively select relationships to query users for their<br /> labels. Experimental results show that with only a few user corrections, the<br /> accuracy of inferring social ties can be significantly improved. Finally, to scale<br /> the model to handle real large networks, a distributed learning algorithm has<br /> been developed.</p>
Article
Nano Letters
<p>We report the first successful application of an ordered bicontinuous double-gyroid vanadium pentoxide network in an electrochromic supercapacitor. The freestanding vanadia network was fabricated by electrodeposition into a voided block copolymer template that had self-assembled into the double-gyroid morphology. The highly ordered structure with 11.0-nm-wide struts and a high specific surface to bulk volume ratio of 161.4 /µm is ideal for fast and efficient lithium ion intercalation/extraction and faradaic surface reactions, which are essential for high energy and high power density electrochemical energy storage devices. Supercapacitors made from such gyroid-structured vanadia electrodes exhibit a high specific capacitance of 155 F/g&nbsp; and show a strong electrochromic color change from green/gray to yellow, indicating the capacitor's charge condition. The nanostructuring approach, and utilizing an electrode material which has intrinsic electrochemical color-change properties, are concepts that can be readily extended to other electrochromic intercalation compounds.</p>
Article
Chinese Computer Federation journal
<p>Online social networks (online social network) provide people with a sharing of content, instant communication, expanding the social platform. With the popularity of smart mobile devices such as smart phones, and mobile data transmission technology, social networking is rapidly advancing to the mobile terminal from the PC side, there has been a large number of new applications for mobile terminals and services. The mobile social network (mobile social networking) has been widespread concern in industry and academia. So, in the end what is a mobile social network? Is it an extension of online social networking but on the mobile? How to provide a better experience to users through mobile social networking? In this paper, we propose the concept of instantaneous social networking (Ephemeral Social Networking), describing how to use the instantaneous social networks to provide users with a truly mobile social networking experience, and discuss some research issues and challenges.</p> <p>&nbsp;</p> <p>&nbsp;</p>
In Proceedings
Proceedings of the ACM SIGCHI Conference on Human Factors in Computing Systems
ACM
Article
IEEE Transactions on Parallel and Distributed Systems
In Proceedings
ACM SIGCHI Conference on Human Factors in Computing Systems
ACM
Conference
IEEE International conference on Audio, Speech and Signal Processing (ICASSP)
IEEE

2014

Conference
2014 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
2014 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
A standard-throughput-approaching LDPC decoder has been implemented on a mid-range GPU in this paper. Turbo-Decoding Message-Passing algorithm is applied to achieve high throughput. Different from traditional host managed multi-streams to hide host-device transfer delay, we use kernel maintained data transfer scheme to achieve implicit data transfer between host memory and device shared memory, which eliminates an intermediate stage of global memory. Data type optimization, memory accessing optimization, and low complexity Soft-In Soft-Out algorithm are also used to improve efficiency. Through these optimization methods, the 802.11n LDPC decoder on NVIDIA GTX480 GPU, which is released in 2010 with Fermi architecture, has achieved a high throughput of 295Mb/s when decoding 512 codewords simultaneously, which is close to highest bit rate 300Mb/s with 20MHz bandwidth in 802.11n standard. Decoding 1024 and 4096 codewords achieve 330 and 365Mb/s. A 802.16e LDPC decoder is also implemented, 374Mb/s (512 codewords), 435Mb/s (1024 codewords) and 507Mb/s (4096 codewords) throughputs have been achieved.

2013

Article
Neurocomputing
With the proliferation of mobile devices and multimedia, videos have become an indispensable part of life-logs for personal experiences. In this paper, we present a real-time and interactive mobile application for home video summarization on mobile devices. The main challenge of this method is lack of information about the video content in the following frames, which we term “partial-context” in this paper. First of all, real-time segmentation algorithm based on partial-context is applied to decompose the captured video into segments in line with the change in dominant camera motion. Secondly, an original key frame update strategy is presented to optimize selected key frames in such partial-context. In addition, the main challenge to conventional video summarization is the semantic understanding of the video content. Thus, we leverage the fact that it is easy to get user input on a mobile device and attack this problem through the user interaction. The user preference is learned and modeled by a Gaussian Mixture Model (GMM) whose parameters are updated each time when users manually select a key frame. Our system utilizes the user preferences to optimize the key frame update process. Evaluation results demonstrate that our system significantly improves users experience and provides an efficient automatic/semi-automatic video summarization solution for mobile users.
Conference
MobileHCI'13
ACM
We present a study that investigates the potential of combining, within the same interaction cycle, deformation and touch input in a handheld device. Using a flexible, input-only device connected to an external display, we compared a multitouch input technique and two hybrid deformation-plus-touch input techniques (bending and twisting the device, plus either front- or back-touch), in an image-docking task. We compared and analyzed the performance (completion time) and user experience (UX) obtained in each case, using multiple assessment metrics. We found that combining device deformation with front-touch produced the best UX. All the interaction techniques showed the same efficiency in task completion. This was a surprising finding, since multitouch (an integral input technique) was expected to be the most efficient technique in an image docking task (an interaction in an integral perceptual space). We discuss these findings in relation to self-reported qualitative data and observed interaction-procedure metrics. We found that the interaction procedures with the hybrid techniques were more sequential but also more paced. These findings suggest that the benefits of deformation input can still be observed when deformation and touch are combined in an input device.
Conference
Proceedings of the SIGCHI Conference on Human Factors in Computing Systems - CHI '13
ACM Press
We present a comparative evaluation of two touch-based group-binding methods, a leader-driven method and a peer-based method, against a more conventional group-binding method based on scanning and passwords. The results indicate that the participants strongly preferred the touch-based methods in both pragmatic and hedonic qualities as well as in the overall attractiveness. While the leader-driven method allowed better control over the group and required only one participant to be able to form a group, the peer-based method helped to create a greater sense of community and scaled better for larger group sizes and distances. As the optimal group-binding method depends on the social situation and physical environment, the binding methods should be flexible, allowing the users to adapt them to different contexts of use. For determining the order of the devices, manual arrangement was preferred over defining the order by touching.
Conference
IEEE ICC'13 - Workshop on Small Wireless Networks (SmallNets)
We calculate the optimal muting ratio for time domain Enhanced Inter-Cell Interference Coordination (TDM eICIC) in a downlink HetNet scenario, consisting of macrocell and femtocell users. First we derive analytically the optimal muting ratio in a simplified scenario, and identify a particular case where all macro users are either strongly or not at all affected by the presence of femtocells. In this case, the optimal muting ratio can be calculated from parameters that can be simply estimated by the network. Furthermore, we solve by numerical optimization the optimal muting ratio in a simulated HetNet scenario, and find that most of the network instances are described by this particular case. We conclude that in a typical femto-macro heterogeneous network, an optimal muting ratio can be approximated by a simple calculation based on parameters that can be estimated by the network.
Conference
Proceedings of the 6th International Conference on Designing Pleasurable Products and Interfaces - DPPI '13
ACM Press
User experience (UX) has been recognized as an important quality factor of interactive products and services. Current design practices aim at ensuring a generally pleasurable or satisfying UX. However, approaches and methods for designing for specific experiences are still scarce. This paper addresses experience-driven design (EDD) by reflecting upon a study where playful experiences (PLEX) were utilized as design targets in a practical design assignment of a post-graduate seminar. The outcomes and learning experiences imply that utilizing PLEX as target experiences in the EDD approach is a sound way to provide design inspiration and guidance, and help refining early design ideas. The pre-defined playful experiences were considered as fruitful starting points for brainstorming as well as constant reminders of the rationale of the design. The paper concludes with reflections on applying EDD and four roles in which it was found beneficial: guiding & framing, inspiring, evaluating and communicating.
Article
Journal of Acoustic Society of America
Transient signals such as plosives in speech or castanets in audio do not have a specific modulation or periodic structure in time domain. However, in the spectral domain they exhibit a prominent modulation structure, which is a direct consequence of their narrow time localization. Based on this observation, a spectral-domain AM-FM model for transients is proposed. The spectral AM-FM model is built starting from real spectral zero-crossings. The AM and FM correspond to the spectral envelope (SE) and group delay (GD), respectively. Taking into account the modulation structure and spectral continuity, a local polynomial regression technique is proposed to estimate the GD function from the real spectral-zeros. The SE is estimated based on the phase function computed from the estimated GD. Since the GD estimation is parametric, the degree of smoothness can be controlled directly. Simulation results based on synthetic transient signals generated using a beta density function are presented to analyze the noise-robustness of the SE-GD model. Three specific applications are considered: (i) SE-GD based modeling of castanet sounds; (ii) appropriateness of the model for transient compression; and (iii) determining glottal closure instants in speech using a short-time SE-GD model of the linear prediction residue
Conference
The 2013 IEEE International Conference on Multimedia and Expo (ICME 2013)
To date, human hand detection in images remains a challenging task due to the variable lighting conditions, hand appearances and background noise. In this paper, we present an effective strategy based on feature fusion for detecting hands with cluttered surroundings. To form the fusions, we propose three novel noise invariant features, namely: 1) NCHOG (Noise Compensated Histogram of Oriented Gradients), 2) NCLBP (Noise Compensated Local Binary Patterns), and 3) HPCP (Histograms of Pairs of Circumference Pixels). We show the superior performance of the NCHOG and the NCLBP descriptors over their existing traditional counterparts, i.e., HOG and LBP. Merging our novel features with existing features in different permutations, and applying Partial Least Squares (PLS) based feature weighting, yields excellent detection results on our own dataset of hand images with variegated and complex backgrounds.
Article
Pervasive and Mobile Computing Journal
This Special Issue is a follow-up of the the Mobile Data Challenge (MDC), a community-based research initiative on smartphone data analysis that started in 2011 and was finalized as a workshop event in Newcastle, U.K. in June 2012. The MDC, co-organized by Nokia Research Center Lausanne and Idiap Research Institute, was created around the Lausanne Data Collection Campaign (LDCC) resources. This smartphone data was collected from close to 200 users for over a year of time in the Lake Geneva region in Switzerland. After releasing the data to over 500 individual researchers worldwide and receiving over 100 challenge submissions, the MDC Workshop featured 40 smartphone data based papers on a variety of topics related to descriptive analysis, mining, classification, and visualization of mobility, connectivity, and communication. The momentum created by the challenge and related workshop motivated us to contribute a Special Issue that would feature some of the best ideas originating from the MDC. In July 2012 authors of a total of 11 papers (including the six winners of the various awards given at the MDC Workshop) were invited to substantially extend their work and submit a journal version of their initial contributions. Additionally, an overview paper about the Mobile Data Challenge was co-authored by the core research team at Nokia and Idiap and submitted for review. The papers were subject to peer review following the regular PMC process, in which reviewers were appointed by the Guest Editors. The review of the overview paper was handled by Dr. George Roussos as an Area Editor. The evaluation process (involving in most cases two review rounds) resulted in acceptance of 11 papers for publication.
Conference
17th International Conference: Information Visualisation
This paper studies a MoodPic concept and a prototype implementation enabling collaborative creation of mood picture based musical playlists, evaluated qualitatively with 30 Finnish participants. In general, MoodPic was found to be a successful concept and stated to add novel experiences to music listening. Accessing music through mood pictures was highly appreciated and seen as a good way to discover new music over the genre boundaries and receive music recommendations from real users based on their mood picture interpretation. Sorting music based on mood pictures instead of genres was seen as an interesting and easy way to interact with music. Based on the interview results, this paper introduces several ideas for further improving the music listening experience using mood pictures as a basis for playlists. This paper summarizes the main findings and proposes an extensive set of generalized design implications to take into account when designing solutions for social music discovery.
Conference
IEEE WCNC
IEEE
This paper presents the system performance analysis of 3GPP Long-Term Evolution (LTE) and IEEE 802.11 Wireless Local Area Networks (WLAN) in a situation where LTE downlink (DL) has been expanded over to unlicensed frequency band usually used by WLAN. Simple fractional bandwidth sharing mechanism is used to allow both technologies to transmit. The system performance is evaluated by means of fully dynamic network simulations.
Conference
ICASSP 2013 - 2013 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)2013 IEEE International Conference on Acoustics, Speech and Signal Processing
IEEE
This paper presents the design of multiple-input multiple-output (MIMO) coordinated beamforming (CBF) techniques that greatly decrease packet decoding failure due to collisions at co-channel 802.11 WLAN access points (APs). Specifically, we advocate a new WLAN paradigm that promotes the sharing of channel state information (CSI) and uplink precoders between co-channel APs that are capable of multipacket reception (MPR). PHY-layer MIMO CBF design algorithms based on joint and sequential computation that satisfy network-wide MPR conditions are presented. Numerical examples illustrate that the proposed CBF schemes greatly outperform uncoordinated methods in terms of successful packet detection.
Article
Pervasive and Mobile Computing
This paper presents an overview of the Mobile Data Challenge (MDC), a large-scale research initiative aimed at generating innovations around smartphone-based research, as well as community-based evaluation of mobile data analysis methodologies. First, we review the Lausanne Data Collection Campaign (LDCC) { an initiative to collect unique, longitudinal smartphone data set for the MDC. Then, we introduce the Open and Dedicated Tracks of the MDC; describe the speci c data sets used in each of them; discuss the key design and implementation aspects introduced in order to generate privacy- preserving and scienti cally relevant mobile data resources for wider use by the research community; and summarize the main research trends found among the 100+ challenge submissions. We nalize by discussing the main lessons learned from the participation of several hundred researchers worldwide in the MDC Tracks.
Miscellaneous
This document describes a method for detecting the presence of DNS64 and for learning the IPv6 prefix used for protocol translation on an access network. The method depends on the existence of a well-known IPv4-only fully qualified domain name "ipv4only.arpa.". The information learned enables nodes to perform local IPv6 address synthesis and to potentially avoid NAT64 on dual-stack and multi-interface deployments.
Article
Journal of New Music Research
This article describes the evaluation and comparison of five prototypes designed for the discovery of new music. The prototypes were compared against each other using various qualitative and quantitative metrics, and the results were then used to formulate a set of design criteria for future music discovery applications. Based on the results of a user study with 40 participants, visually interesting user interfaces and new interaction paradigms can inspire users to explore music collections and provide playful and fun ways to find new music. Without textual search functionality, such applications should rather complement than replace traditional music-listening applications.
In Proceedings
ICASSP 2013
IEEE
The use of cepstral coefficients derived from a filter bank with logarithmically spaced band center frequencies and Gaussian mixture models (GMMs) with quantized parameters (qGMMs) are proposed for accelerometer-based activity recognition of mobile phone users. The use of a filter bank with logarithmically spaced band center frequencies is shown to yield better results than the use of a filter bank with linear spacing between band center frequencies. GMMs and qGMMs are shown to achieve similar recognition accuracies. However, the computation time using qGMMs is shown to be either at the same level or faster when compared to GMMs, depending on model complexity. Using the proposed approach, we achieve an accuracy of 72.6% and 91.3% on two recognition tasks with seven and five activities, respectively.
Article
IEEE Communications Magazine
The reforms in spectrum management aim toward more efficient, flexible, and shared use of spectrum, while fostering innovation and competition in mobile communications. The goal is to have affordable wireless broadband and make Internet access a human right. To achieve this goal, the regulators need to identify, evaluate, and decide between the different spectrum access models. This article presents a taxonomy of the models, which is based on priorities between the different users of spectrum. For example, the low priority systems may be allowed to use the spectrum only if the high priority systems are not occupying the frequency. The hierarchy of the systems can be implemented using different technologies such as centralized databases or distributed sensing devices. The taxonomy clarifies the regulatory alternatives and emphasizes the differences in ownership and usage rights. The new models can be incorporated in the auction design in order to estimate their value to the companies, and this reflects the recent trend of supporting spectrum management with market- based methods.
Conference
Asilomar Conference on Signals, Systems, and Computers, 2013
The recent digital transition of TV broadcasting has created new opportunities for wireless usage for voice, video and data services in these newly released bands (known as TV white spaces). Some possible wireless technologies that can be deployed in this new spectrum are LTE and Wi-Fi. In this paper, we conduct an in-depth analysis of the physical layer performance of LTE and Wi-Fi in the presence of cross-technology interference. We propose a physical layer simulation framework in order to co-simulate the link level performance of LTE and Wi-Fi and show the impact of different interference patterns on the error rate. Our results show that the Wi-Fi performance is slightly exacerbated in the presence of LTE interference (compared to similar Wi-Fi interference). We also show that LTE pilot boosting has negligible impact onWi-Fi performance. Finally, we also show the impact of Wi-Fi interference on the LTE performance.
Conference
ICC 2013 - 2013 IEEE International Conference on Communications (ICC)
IEEE
The recent development of regulatory policies that permit the use of TV bands spectrum on a secondary basis has motivated discussion about coexistence of primary (e.g. TV broadcasts) and secondary users (e.g. WiFi users in TV spectrum). However, much less attention has been given to coexistence of different secondary wireless technologies in the TV white spaces. Lack of coordination between secondary networks may create severe interference situations, resulting in less efficient usage of the spectrum. In this paper, we consider two of the most prominent wireless technologies available today, namely Long Term Evolution (LTE), and WiFi, and address some problems that arise from their coexistence in the same band. We perform exhaustive system simulations and observe that WiFi is hampered much more significantly than LTE in coexistence scenarios. A simple coexistence scheme that reuses the concept of almost blank subframes in LTE is proposed, and it is observed that it can improve the WiFi throughput per user up to 50 times in the studied scenarios.
Conference
Proceedings of the 6th International Conference on Designing Pleasurable Products and Interfaces - DPPI '13
ACM Press
The Playful Experiences (PLEX) framework is a categorization of playful experiences based on previous theoretical work on pleasurable experiences, game experiences, emotions, elements of play, and reasons why people play. While the framework has been successfully employed in design-related activities, its potential as an evaluation tool has not yet been studied. In this paper, we apply the PLEX framework in the evaluation of two game prototypes that explored novel physical interactions between mobile devices using Near-Field Communication, by means of three separate studies. Our results suggest that the PLEX framework provides anchor points for evaluators to reflect during heuristic evaluations. More broadly, the framework categories can be used as a checklist to assess different attributes of playfulness of a product or service.
Article
ACM SIGCOMM Computer Communication Review
The participation of the network research community in the Internet Standards Development Organizations (SDOs) has been relatively low over the recent years, and this has drawn attention from both academics and industry due to its possible negative impact. The reasons for this gap are complex and extend beyond the purely technical. In this editorial we share our views on this challenge, based on the experience we have obtained from joint projects with universities and companies. We highlight the lessons learned, covering both successful and under-performing cases, and suggest viable approaches to bridge the gap between networking research and Internet standardization, aiming to promote and maximize the outcome of such collaborative endeavours.
Conference
Future Network & Mobile Summit 2013
The overall goal of the METIS project is to lay the foundation for the beyond 2020 5G wireless communication systems by providing the technical enablers needed to address the very challenging requirements foreseen for this time frame. The major challenges in this context are three-fold: 1) The mobile and wireless traffic volume is expected to increase a thousand-fold over 2010 figures. 2) The number of wirelessly-connected devices will count in tens of billions. 3) The variety of applications and data traffic types will be significantly larger than today, which will result in more diverse requirements on services, devices etc. This paper describes the five METIS scenarios that are based on the fundamental challenges that have been identified for 5G systems, and which will drive the research in the METIS project.
Conference
IEEE Vehicular Technology, Spring 2013
The deployment of modern mobile systems has faced severe challenges due to the current spectrum scarcity. The situation has been further worsened by the development of different wireless technologies and standards that can be used in the same frequency band. Furthermore, the usage of smaller cells (e.g. pico, femto and wireless LAN), coexistence among heterogeneous networks (including amongst different wireless technologies such as LTE and Wi-Fi deployed in the same frequency band) has been a big field of research in the academy and industry. In this paper, we provide a performance evaluation of coexistence between LTE and Wi-Fi systems and show some of the challenges faced by the different technologies. We focus on a simulator-based system-level analysis in order to assess the network performance in an office scenario. Simulation results show that LTE system performance is slightly affected by coexistence whereas Wi-Fi is significantly impacted by LTE transmissions. In coexistence, the Wi-Fi channel is most often blocked by LTE interference, making the Wi-Fi nodes to stay on the LISTEN mode more than 85% of the time. This reflects directly on the Wi-Fi user throughput, that decreases from 50% to ~100% depending on the scenario. Finally, some of the main issues that limit the LTE/Wi-Fi coexistence and some pointers on the mutual interference management of both the systems are provided.
Conference
IEEE VTC WMCR Fall 2013
IEEE VTC
Spectrum sensing scheduling policies are proposed to find spectrum opportunities for wide-band cognitive radios by taking into account realistic reconfiguration energy consumptions and time delays. The first policy relies on the RF environment Markov properties. Thus, it may become computationally demanding. The second sub-band selection policy based on Qlearning is proposed to circumvent this. Performance of the two policies are compared and discussed against a performance upper-bound of the optimal solution to the corresponding partially observable Markov decision process formulation. The suitability of the Q-learning technique is validated by showing that it achieves good performance in simulation.
Conference
Military Communications Conference (MILCOM)
IEEE MILCOM
Spectrum congestion is a problem to both commercial and military systems. A recent Presidential Council of Advisors on Science and Technology (PCAST) study suggests that this problem is further amplified for military systems because not only demand for more bandwidth is increasing but portion of the military licensed bands is recommended for commercial use. PCAST report also suggests that spectrum congestion is mainly due to inefficient use of spectrum rather than the spectrum scarcity. This paper deals with challenges evolving due to coexistence of various commercial and military communications systems in wideband non-contiguous spectrum. A non-contiguous spectrum environment is characterized by spectrum holes fragmented across frequency range of interest. This paper, in particular, focuses on different types of interference which will affect the quality of a spectrum hole and its utility for spectrum sharing application. Furthermore, we also discuss the impact of spectrum sharing from the system perspective including hardware design, physical (PHY) layer intricacies, and medium access control (MAC) layer spectrum management. Since the number of spectrum holes required is application dependent, noncontiguous waveform design and pertinent design modifications and MAC layer improvements are also an intrinsic part of this paper.
Article
International Journal of Arts and Technology
Playfulness can be observed in all areas of human activity. It is an attitude of making activities more enjoyable. Designing for playfulness involves creating objects that elicit a playful approach and provide enjoyable experiences. In this paper, we introduce the design and evaluation of the PLEX Cards and its two related idea generation techniques. The cards were created to communicate the 22 categories of a playful experiences framework to designers and other stakeholders who wish to design for playfulness. We have evaluated the helpfulness of both the cards and their associated techniques in two studies. The results show that the PLEX Cards and its associated techniques are valuable sources of inspiration when designing for playfulness.
Article
IEEE Communications Magazine
Operator controlled IP traffic offloading in cellular networks has been a lively topic in both product and standard development during recent years. Specifically, 3GPP has developed multiple IP traffic offloading solutions for their system architecture, typically requiring 3GPP-specific modifications for user equipment. We argue that an adequate lightweight access technology agnostic IP traffic offloading system is achievable with a generic internet layer solution. Such a solution can still utilize 3GPP system properties for operators to push offloading policies securely into mobile devices. We discuss existing 3GPP-specified offloading solutions and present three variations of our internet layer traffic offloading implementations, and compare them against 3GPP-specified solutions. Our hands-on experience in operator networks shows that such a direction is feasible and promising.
Article
Neurcomputing Special Issue
Nowadays, hand gesture interaction is an emerging way for mobile applications. Robust hand detection is a crucial step in this task. Due to limited computing capability on mobile devices, it’s not practical to deploy heavy algorithms. Traditional frame difference based methods are efficient but may fail in some situations and lead to the frame delay, loss of target or false detection. To deal with these problems, an effective and efficient algorithm is proposed which computes the frame differences in a one-against-all way. The intersection of the differences is obtained as candidate target area. A coarse-to-fine refinement process is designed in the next step to extract the exact target area of hand. In differential operation, the utilization of Hamming distance between LBP features and local adaptive threshold mechanism improves the robustness of detection to illumination variation. Experiments show that the proposed method obtains much higher accuracy compared to traditional methods.
Conference
Battery Manufacturing 2013
Mobile devices become ever more capable and make increasing demands on their onboard energy storage. Allied to the primary demand for storage capacity are requirements for slimness, durability, safety and increasingly, the design freedom afforded by flexibility. We will discuss forthcoming trends in mobile devices and the expected needs for energy storage.
In Proceedings
CHI'13
ACM
MARSUI is a hardware deformable prototype exhibiting plastic (shape-retaining) behavior. It can track the shape that the user creates when deforming it. We envision that a set of predefined shapes could be mapped onto particular applications and functions. In its current implementation, we present three shapes that MARSUI can be deformed into: circular band, flat surface and sharp bent. These shapes map respectively onto the following applications: wristwatch, mobile phone and media player. Since the malleable interface can also take other forms, feedback plays an important role in guiding the user towards the predefined shapes. In this paper, we focus on investigating the possibilities that auditory feedback could offer in guiding the user towards reaching the intended shapes.
Conference
CHI '13 Extended Abstracts on Human Factors in Computing Systems - CHI EA '13
ACM Press
In this paper, we explore the interaction design space for interactive glasses. We discuss general issues with interactive glasses (i.e., optics, technology, social, form factors), and then concentrate on the topic of the nature of interaction with glasses and its implications to provide a delightful user experience with the NotifEye.
Article
IEEE Communications Magazine, Special Issue on Heterogeneous and Small Cell Networks (HetSNets)
In this paper, energy efficient methods for inter-frequency small cell discovery in heterogeneous networks is discussed under the framework of LTE-Advanced.
Conference
IEEE Radio and Wireless Week
In radio frequency (RF) power amplifiers (PA), power efficiency, linearity and cost are contradictory requirements. In the Long Term Evolution (LTE) and LTE-Advanced (LTE-A) standards by the Third Generation Partnership Project, maximum power reduction (MPR) is used to relax RF PA requirements in user equipment. In this paper, we analyze the gating factors that determine the MPR in multicluster transmission, a new feature in LTE-A that significantly changes the way unwanted emissions are distributed in the spectrum. The analysis can help in devising more advanced MPR formulas and in development of RF PA linearizers.
Conference
Audio Engineering Society Convention 134
Audio Engineering Society
In a continuous mobile communication scenario, e.g., between co-workers, participants may occasionally be located in the same space and thus hear each other naturally. To avoid hearing echoes, the audio transmission between these participants should be cut off. In this paper an acoustic co-location detection algorithm is proposed for the task, grouping participants together based solely on their microphone signals and mel-frequency cepstral coefficients thereof. The algorithm is tested both on recordings of different communication situations and in real time integrated into a voice-over-IP communication system. Tests on the recordings show that the algorithm works as intended, and the evaluation using the voice-over-IP conferencing system concludes that the algorithm improves the overall clarity of communication compared with not using the algorithm. The acoustic co-location detection algorithm thus proves a useful aid in continuous mobile communication systems.