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Son J.-Y.,Konyang University | Lee B.-R.,Electronics and Telecom Research Institute | Kim J.-W.,Korea Electronics Technology Institute | Park M.-C.,Korea Institute of Science and Technology
WIO 2013 - 12th Workshop on Information Optics, Proceedings | Year: 2013

The problems involved with the currently available display devices for electro-holography are induced by the regularity of pixel patterns in these devices. The diffraction patterns induced from the pixel patterns are decreasing the diffraction efficiency of the devices and limiting the image space of the reconstructed image. Added on this diffraction pattern, the regularity of fringe pattern also induces another diffraction pattern which works as an inherent noise in these devices and the display surface accompanied with the reconstructed image. Furthermore, lasers used in these devices can also introduce displayable spectral range reduction and a potential danger to the viewers as the brightness level increases. © 2013 IEEE. Source


Son J.-Y.,Konyang University | Park M.-C.,Korea Institute of Science and Technology | Lee B.-R.,Electronics and Telecom Research Institute
2014 13th Workshop on Information Optics, WIO 2014 | Year: 2014

The moirés appearing in the contact-type 3 dimensional displays are chirped by the thickness of the viewing zone forming optics (VZFO) in the displays. Due to the thickness, the patterns of the display panels for the displays are refracted on to the pattern plane of VZFO to superpose with the pattern on the plane. The moirés formed this way can have chirped fringe patterns, and change numbers and phases of their fringes according to the changes in viewer's viewing positions and viewing angles at a given viewing distance. © 2014 IEEE. Source


Kim J.-B.,Stanford University | Choi J.-W.,Daegu Gyeongbuk Institute of Science and Technology | Cioffi J.M.,Electronics and Telecom Research Institute | Cioffi J.M.,King Abdulaziz University
IEEE Transactions on Communications | Year: 2014

This paper investigates the effect of imperfect channel state information (CSI) on the outage performance of cooperative distributed beamforming (DBF). The acquisition of perfect CSI is disturbed by outdated CSI and channel estimation errors. Decode-and-forward relays are considered with individual power constraints at each relay. Considering a training-and-feedback strategy to acquire CSI, a closed-form approximate expression for outage probability and the achievable diversity gain are first provided under Rayleigh fading channels. Numerical observations verify that the approximation is very tight. It is shown that outdated CSI seriously degrades the performance, and therefore, the outage probability is bounded and no diversity is achieved. Conversely, channel estimation errors cause slight performance degradation, and full diversity order is still achievable. However, even when CSI is outdated, it is shown that the asymptotic outage decreases as the number of relays K increases, where the logarithm of the outage probability decreases at the rate of K\log K. This paper shows that, when the destination re-estimates the current CSI for decoding, the effect of outdated CSI is greatly mitigated and consequently achieves a diversity gain of one. To re-estimate the current CSI with small overhead, the beamformed training sequence (BFTS) strategy is proposed, in which a new closed-form formula for minimum-mean-square-error estimation is presented using Gaussian approximation. Numerical results verify that the outage performance with the proposed BFTS scheme is close to that of a perfect estimation. A closed-form outage expression of DBF with the proposed BFTS scheme is also presented under an assumption of high-signal-to-noise ratio (SNR), but the expression is very tight even in low-to-moderate SNR regimes. © 2014 IEEE. Source


Son J.-Y.,Konyang University | Chernyshov O.O.,Konyang University | Lee B.-R.,Electronics and Telecom Research Institute | Lee H.,Korea Institute of Science and Technology
14th Workshop on Information Optics, WIO 2015 | Year: 2015

The line thickness of lines consisting of the line pattern of VZFO in contact-type 3-D displays is a major clue of simulating the color moirés in the displays. The thicknesses of the lines and the period of the line pattern are virtually chirped due to refraction caused by the VZFO thickness. This chirping and the line thickness are the main source of the color moirés. This color moirés can be used to hide and enhance certain feature of images. © 2015 IEEE. Source


Colmenares J.A.,University of California at Berkeley | Kim K.H.,University of California at Irvine | Zhang Z.,University of California at Irvine | Lim C.,Electronics and Telecom Research Institute | Rim K.-W.,Sun Moon University
ISORC 2010 - 2010 13th IEEE International Symposium on Object/Component/Service-Oriented Real-Time Distributed Computing | Year: 2010

Highly desirable types of networked multimedia applications should adapt to changes in the environmental conditions in which they operate, such as communication bandwidth, available memory, and battery lifetime, while providing the best possible quality of service (QoS). In this paper we present a software architecture that facilitates the development of adaptive networked multimedia applications which meet this requirement. The proposed software architecture is based on the Time-triggered Message-triggered Object (TMO) programming scheme and it is implemented as a thin layer on top of the TMO Support Middleware (TMOSM). The new layer, called the QoS Adaptation Support Layer (QASL), includes monitoring and runtime reconfiguration facilities that allow us to easily incorporate QoS-adaptation capabilities into TMO-based multimedia applications. In addition, we introduce a novel, practical approach for establishing the QoS configurations that guide the adaptive behavior of a networked multimedia application. A QoS configuration contains a set of parameters that specify the quality-related characteristics of the media streams which a receiver expects from a sender. We also present a strategy used in QASL for selecting, from a given set of QoS configurations, an optimal configuration by reflecting currently observed environmental conditions. Finally, the effectiveness of the QoS-adaptation mechanisms implemented in QASL is evaluated with the use of a heterogeneous network based multi-party videoconference application. © 2010 IEEE. Source

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