• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.442-444
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• 2002

본 논문은 인터넷 전화 (Internet Telephony)의 대표적 프로토콜인 SIP의 이동성과 효율적인 네트워크 대역 이용에 관한 연구이다. 이동성을 제공하기 위해 모바일 IP를 사용하기에는 삼각 라우팅, 캡슐화 오버헤드와 같은 단점이 있다고 알려진 것에 비해 이러한 모바일 IP 기반 SIP 애플리케이션의 가능성과 적합성을 보인 기존의 연구 〔1〕에서 더 나아가 무선통신에서 발생하는 핸드오프 동안에도 패킷 손실을 최소화 할 수 있는 패킷 당 오디오 프레임 수의 상관관계를 설계하고, 무선통신 종단 간 물리적 거리 변화에 따라 동적으로패킷 당 프레임 수를 조절하여 적용할 수 있는 적응적 애플리케이션 개발을 위한 표준을 제시한다.

• Proceedings of the Korean Society for Quality Management Conference
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• 2009.10a
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• pp.89-94
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• 2009

In the past few years with the popularization of the Internet using mobile devices such as the universal in the field of information technology has made rapid development and spread, the width and speed of change is also expected to grow much. As a result Internet telephony (VoIP) was to emerging, VoIP as a leader in next-generation converged services, the proliferation of IPTV services, including the successful introduction and subsequent convergence of the early to gauge whether the settlement is much distance in terms of importance. Therefore, this research using the Internet and telephone customer satisfaction survey, and Kano analysis is important from the perspective of the customer requirements by looking at what the Internet phone service in the development and improvement priorities are supposed to be able to stand.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.18-26
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• 1996

In this paper we propose a new dual structured tap selection algorithm for voice echo canceller in digital cellular communication system, investigating adaptive filtering algorithms for echo cancellation in long distance telephony or mobile communication system. The proposed algorithm has a two-stage processing structure that after a dispersive region in an impulse response of an echo path is found out, the tap coefficients of a short length filter are adjusted adaptively for the region, because the impuse response has a very little portion of the dispersion. Simulation results show that the proposed algorithm with 256 taps gives a performance of convergence speed superior to both full-tap normalized least mean with 256 taps gives a performance of convergence speed superior to both full-tap normalized least mean square (NLMS) and a scrub taps waiting in a queue (STWQ) algorithms by about eighty per cent, also to a tap selection algorithm by about twenty per cent. And the resutls diplay that if the more tap coefficients are used due to a long delayed dispersive zone, the proposed algorithm produces the better performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.375-376
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• 2009

모바일 환경 상에서 영상통화는 제한된 대역폭 및 손떨림 현상 등의 문제로 인하여 저품질의 서비스가 제공되고 있다. 기존의 영상통화 환경에서 향상된 품질의 영상통화 서비스를 제공하기 위하여 중요 객체와 비중요 객체를 구분하여 분리하며, 중요 객체에 대해서는 고화질을 갖도록 하는 비디오 압축 방법을 제안한다. 매 프레임 마다 중요 객체와 비중요 객체를 분리하며, 분리된 객체는 다른 비트율과 화질을 갖도록 각 객체에 적합한 변환 커널을 적용하여 부호화 절차를 달리한다. 중요 객체는 저압축, 고화질을 가지도록 부호화하며, 비중요 객체에 대해서는 고압축, 저화질을 가지도록 부호화함으로써 제한된 대역폭 내에서 비트율을 유지하도록 한다.

• Journal of IKEEE
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• v.13 no.4
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• pp.116-124
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• 2009

Recently the CPU performance of modem chipsets or multimedia processors of mobile phone is as high as notebook PC. That is why mobile phone has been emerged as a leading ICON on the convergence of consumer electronics. The various applications of mobile phone such as DMB, digital camera, video telephony and internet full browsing are servicing to consumers. To meet all the demands the image quality has been increasingly important. Mobile phone is a portable device which is widely using in both the indoor and outside environments, so it is needed to be overcome to deteriorate image quality depending on environmental light source. Furthermore touch window is popular on the mobile display panel and it makes contrast loss because of low transmittance of ITO film. This paper presents the image enhancement algorithm to be embedded on image enhancement SoC. In contrast enhancement, we propose Clipped histogram stretching method to make it adaptive with the input images, while S-shape curve and gain/offset method for the static application And CIELCh color space is used to sunlight readability enhancement by controlling the lightness and chroma components which is depended on the sensing value of light sensor. Finally the performance of proposed algorithm is evaluated by using histogram, RGB pixel distribution, entropy and dynamic range of resultant images. We expect that the proposed algorithm is suitable for image enhancement of embedded SoC system which is applicable for the small-sized mobile display.

• Proceedings of the Korea Information Processing Society Conference
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• 2013.05a
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• pp.486-489
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• 2013

현재 IT 인프라 기술이 상당한 발전을 이루고 있으며 고급 인프라를 활용한 IT 기술들이 나날이 발전하고 있다. 지금의 정보화 사회에 지대한 영향을 미치고 있는 인터넷을 포함한 수 많은 IT 정보기술들은 각 사회분야에 걸쳐 해당 분야의 정보의 질을 높이고 있다. CTI (Computer Telephony Integration) 기반 콜센터 시스템 또한 IT 인프라의 발전에 발 맞추어 효율적인 정보 제공을 위한 정보 기술이 상당히 많이 발전해왔다. 기존의 콜센터 시스템은 PSTN 망 기반의 전화 중심의 정보제공만 가능한 반면에, 현재 콜센터 시스템은 PSTN 기반이 아닌 IP 기반 인프라를 활용하여 IP 기반으로 제공할 수 있는 여러 기술을 접목시킨 하나의 통합 솔루션 시스템으로 발전하고 있다. 콜과 관련된 서비스만 제공하는 것이 아니라 Fax, E-mail, Instance Messaging 등 여러종류의 서비스를 제공하기 위해 시스템 구성이 변화하고 있는 추세이다. 하지만 현재 콜센터 시스템은 청각장애인을 위해 제공할 수 있는 서비스가 존재하지 않으며 이에 대한 연구 또한 미비한 상태이다. 이에 본 논문에서는 청각장애인을 위한 서비스 제공을 위해 스마트폰 인프라에서 서비스를 제공 받을 수 있는 CTI 시스템을 설계 하였다.

• Science of Emotion and Sensibility
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• v.13 no.1
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• pp.91-102
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• 2010

This study investigates the dominant degree of product design factors through the process of change of design factors. The previous research suggested a concrete measurement method of dominant designs, but it did not investigate empirically the degree of dominance due to the limited data for changes of designs. In this research, thus, after collecting design data of mobile phones and we measured the dominance and structure change of the designs by year. The analyses showed the following two things. First, in design factors of mobile phone the dominance on the body form and the edge grows more and both of them as dominant design factors tend to converge into the rectangular body form and the round edge, respectively. Second, the dominance on other design factors(e.g. the button type, the open type, whether or not to have digital multimedia broadcasting(DMB) and video telephony functions, the combination of colors and the body color) increases and decreases; and hence, design levels tend to diverge. In conclusion, the measurement of dominance on product design factors contributes to marketing managers and designers who are required to establish a strategy for products under the rapidly changing circumstances of market. This research aims to provide those managers and designers with a guide line for a successful development of new product to prepare for the dominant design from this empirical study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1360-1364
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• 2013

Internet phone, communication cost and easy-to-use low-cost compared to the PSTN is a mobile phone of a conventional, and use of the Internet phone is spreading. Construction as part of the broadband convergence network(BCN), Internet service provider(KT, SKT, LGU+) has converted to Internet phone telephone network to all government agencies. In addition, members of the public also have an Internet phone service that you are using. In this paper, we analyze the hacking attack on IP-PBX in the IETF SIP-based that are used in Internet telephony, to the study. The test bed is constructed in the same way as the Internet telephone system to perform studies carried hacking attacks on IP-PBX, analyze the results and to extract evidence forensics. When used in crime by hacking the Internet telephone, we propose a method which can be used as evidence in forensic having legal effect.

• The Journal of Information Systems
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• v.20 no.3
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• pp.257-277
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• 2011

The current study categorizes factors of smartphone into three, using KANO model: attractive factors which cause only product satisfaction, must-be factors for dissatisfaction, and one-dimensional factors for both. Based on it, it presents a new model for the effects that smartphone factors have on satisfaction or dissatisfaction. The purpose is to theoretically explain that smartphone factors on which companies and users place a high value can actually affect satisfaction or dissatisfaction. After choosing 15 factors out of 25 which had been selected through literature study, these were divided into attractive, must-be, and one-dimensional ones. 93 out of 109 questionnaires returned were used for analysis. After frequency analysis using SPSS were conducted on the surveys, the factors were grouped, based on KANO table. The grouping results are as follows. Attractive factors include 'expansion slots for external memory, battery desorption, brand awareness, mobile banking and internet telephony'. Must-be ones include 'multi-touch, information security, entertainment, information retrieval, location based service and SNS. Finally, 'screen visibility, size of internal memory, the amount of internal memory, battery life, and response to after-sales service' are classified as one-dimensional factors. A critical finding of this paper is that since the results are different depending on the operating system of smartphones, it must be taken into consideration in studies on smartphones. The wide and rapid spread of smartphones has changed people's lifestyle as well as business environment, which forces companies to compete with each other to adapt to the changed circumstances. In this competitive system, studies on smartphone factors of satisfaction and dissatisfaction are essential for firms to establish a new strategy. From this point of view, the present paper is expected to be a basic material for enterprises not only to develop goods and services that maximize customer satisfaction and minimize dissatisfaction, but also to establish the future business strategy.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.37-44
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• 2000

In this paper, we described the real-time implementation effort of MPEG-4 audio HVXC (Harmonic Vector eXcitation Coding) algorithm for very low bitrates, which has target applications from mobile communications to Internet telephony, on current high performance floating point TMS320C6701 DSP. We adopted a hardware structure for real-time operation. In order for software optimization, we used C- and assembly-language level optimizations for time-critical functional codes. Utilizing the internal program memory of the DSP as the program cache, the internal data memory overlap technique and DMA functionality, we could get a goal of realtime operation of HVXC codec both at 2 kbit/s and at 4 kbit/s. For an encoder at 2 kbit/s, the optimization ratio to original code is about 96 %. Finally, we got the subjective quality of MOS 2.45 at 2 kbit/s from an informal quality test.