• The Journal of the Korea Contents Association
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• v.8 no.8
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• pp.111-118
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• 2008

Nowadays, people get images from various media like TV, magazines, newspaper, internet. Such images directly influence people's thoughts and lives, either consciously or unconsciously. In the past, reproduction devices have been mainly used in reproducing an original scene accurately. Lately, the cognitive preference became a key value in the scene reproduction, and it was affected by the surrounding media. Recently, the most commonly used device in reproducing an original scene is the camera. The core of an image is the light, in other words, the exposure. Most digital cameras are set to adjust exposure automatically in order to reproduce a scene physically as identical as possible. However, physically right exposure does not always give images that people prefers. Numbers of tests were done to find the exposure value that makes an image cognitively more preferred. Skin tones which are highly sensitive to color and changes in density has been used in the tests. A male and a female model have been used to classify changes in cognitive preference due to gender differences.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.353-359
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• 2014

Recently, the use of mobile devices has increased, and mobile traffic is growing rapidly. In order to deal with such massive traffic, cognitive radio (CR) is applied to efficiently use limited-spectrum resources. However, there can be multiple communication systems trying to access the white space (unused spectrum), and inevitable interference may occur to cause mutual performance degradation. Therefore, understanding the effects of interference in CR-based systems is crucial to meaningful operations of these systems. In this paper, we consider a long-term evolution (LTE) system using additional spectra by accessing the TV white space, where low-power devices (LPDs) are licensed primary users, in addition to TV broadcasting service providers. We model such a heterogeneous system to analyze the co-existence problem and evaluate the interference effects of LPDs on LTE user equipment (UE) throughput. We then present methods to mitigate the interference effects of LPDs by 'de-selecting' some of the UEs to effectively increase the overall sector throughput of the CR-based LTE system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.6
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• pp.37-42
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• 2009

Cognitive radio (CR), which is proposed as a technology that utilizes the frequency resources effectively, has studied to relive scarcity of the frequency resources. Also, FCC revises the regulation to reuse the TV white spaces for applying CR system and allows to use the TV white spaces by CR devices and use of CR device may be regularized after conversion by DTV in 2009. If CR system's signal appeared in pilot's position, pilot sensing performs false alarm detection because pilot sensing scheme confuse DTV signal and CR system. In order to improve false alarm detection, we propose distinction scheme between DTV and CR system using PN511 sequence in this paper.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.132-138
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• 2008

Recently, many frequency sharing technology including CR (Cognitive Radio) technology have been studied actively because of frequency scarcity. For implementing CR systems, spectrum sensing technology plays key role. In IEEE 802.22 WRAN, the first standard aimed at Internet service in a TV channel with CR technology. This paper explained the various spectrum sensing schemes detecting narrowband ATSC signal in the IEEE 802.22 such as Energy detector, Spectral Correlation Sensing scheme, Covariance based Sensing algorithm and analyzed in terms of the probability of misdetection when the probability of false alarm is 10%. Based on simulation results, this paper proposed a duplex sensing scheme based on Energy detector and analyzed the capability of the proposed sensing scheme comparing with each sensing scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.666-675
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• 2008

The IEEE 802.22 standard is being developed with the target of improving the efficiency of spectrum utilization and importing the new wireless communication service. The WRAN standard based on Cognitive Radio is being processed for sharing TV bands. In this paper, the efficient spectrum allocation scheme and the optimal power allocation scheme, Partial Constant Power Water Filling (PCPWF), are proposed to maximize the channel capacity and spectrum efficiency and minimize the interference between adjacent cells. And we maximize the system throughput and fairness by using proposed dynamic cell plan that efficiently allocates channel. The results of the simulations are presented to verify the utilization of our proposed scheme.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.19-23
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• 2016

This paper presents a novel design for dual-band bandpass filters. The proposed filters are applicable to the carrier aggregation of the TV white space (TVWS) band and long-term evolution (LTE) band for cognitive radio applications. The lower passband is the TVWS band (470-698 MHz) whose fractional bandwidth is 40 %, while the higher passband is the LTE band (824-894 MHz) with 8 % fractional bandwidth. Since the two passbands are located very close to each other, a transmission zero is inserted to enhance the rejection level between the two passbands. The TVWS band filter is designed using magnetic coupling to obtain a wide bandwidth, and the LTE band filter is designed using dielectric resonators to achieve good insertion loss characteristics. In addition, in the proposed design, a transmission zero is placed with cross-coupling. The proposed dual-band bandpass filter is designed as a two-port filter (one input/one output) as well as a three-port filter (one common input/two outputs). The measured performances show good agreement with the simulated performances.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7C
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• pp.672-679
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• 2006

Cognitive radio, which is designed to dynamically adapt its transmission to the environments, is believed to be one of the fundamental techniques for future spectrum utilization. As the first step of cognitive radio, spectrum sensing is treated as the most important technique, through which cognition is well explained. In this paper, we propose a spectral correlation based detection method for spectrum sensing. An unlicensed secondary user system operating in TV broadcast bands is taken as an example. Based on the cyclostationarity of communication signals, spectral correlation function is used to minimize the effect of random noise and interference. Energy measurement and peak detection based criteria are proposed. Simulation results show that the proposed detection method outperforms the energy detection and is more suitable for spectrum sensing in cognitive radios.

• Journal of Communications and Networks
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• v.16 no.6
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• pp.600-612
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• 2014

In this paper, we consider the problem of spectrum sensing for advanced television systems committee (ATSC) digital television (DTV) signal detection. To exploit the cyclostationarity of the ATSC DTV signals, we employ spectral correlation density (SCD) as the decision statistic and propose an optimal detection algorithm. The major difficulty is in obtaining the probability distribution functions of the SCD. To overcome the difficulty, we probabilistically model the pilot frequency location and employ Gaussian approximation for the SCD distribution. Then, we obtain a practically implementable detection algorithm that outperforms the industry leading systems by 2-3 dB. We also propose various techniques that greatly reduce the system complexity with performance degradation by only a few tenths of decibels. Finally, we show how robust the system is to the estimation errors of the noise power spectral density level and the probability distribution of the pilot frequency location.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.3
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• pp.51-58
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• 2010

According to dramatic increase of wireless communication demand, more spectrum resources are needed to support considerable and various wireless services, so cognitive radio(CR) was proposed to reuse unused frequency efficiently. Also, FCC revises its policies regarding the usage of the TV white spaces by unlicensed users. CR is an intelligent wireless communication system that is aware of the radio environment and is capable of adapting its operation to the statistical variations. Spectrum sensing is the key task of the CR systems. However, since spectrum sensing performance changes according to the received signal that is received various geography environment, regional characteristics are considered to estimate the path-loss. Therefore, for more accurate analysis and simulation, we demonstrate the spectrum sensing performance of CR system by various method applying Okumura-hata propagation model.

• Korean journal of communication and information
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• v.48
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• pp.231-256
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• 2009

The purpose of this study is that we regard the notion of reality that television viewers feel as presence, point out problem of measurement tool that appropriate for TV, clarify the subordinate concept of presence, and develop measurement tool that have reliability and validity. To achieve this, we paid attention to reality of television as a determinant of presence and tried to elicit proper subcategories. That is, we progressed two steps research that distinguished external characteristic and content of the media into sensible reality and cognitive reality, and develop measure item and verified statistical validity. We analyzed the second research result about measurement category of presence selected by first research and then we did Exploratory factor analysis and Confirmatory factor analysis. As a result, the first characteristic that make people experience presence is sensible reality, that is, it is the factor of sensible faithfullness, image faithfullness, and image reality as the form factor of the media. The second characteristic is cognitive reality. That is the factor of social reality, relational reality, and practical reality as the factor of media content. Synthesizing these subordinate factor, we can conceptualize presence experience as a reality of media form and content in HDTV viewing environment.