• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.2
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• pp.192-201
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• 1993

According to technical advances of telecommunication, communication network has changed to digital transmission from analog transmission network. In the long run, current network will be altered into ISDN which makes end-to-end digital communication. This transition of communication network brings about an important questions for networking plan, administration, and speech quality in order to achieve the effective and advanced telecommunication. Speech quality criterions and degradation factors of digital communication system differ from those of existing analog system because of other characteristics like single echo. It is, therefore, necessary to design new criterions and specifications for digital communication network. This Paper describes the relation between speech communication and speech transmission quality and describes the implementation of model system for quality evaluation of digital speech communication network. In addition, some applications of model system implemented are proposed.

• Informatization Policy
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• v.18 no.2
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• pp.85-98
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• 2011

This paper attempts to develop an index of mobile telecommunications service quality through econometric analysis using data of the leading telco in each OECD country. CapEx of the operator was selected as a proxy variable to represent the quality of the service. To eliminate the part which is dependent on the population and size from CapEx, however, CapEx was regressed on population, area, 3G coverage, Herfindahl-Hirschman Index (HHI) of mobile market, EBITDA margin, and market share of the leading operator. Then, the part of CapEx, which was explained by size and population, was subtracted from CapEx, and the remaining part was regarded as the quality index of mobile telecommunications service. Comparisons among quality indexes of each country revealed that the service quality in Korea and Japan is better than that of France, UK and Germany.

• Electronics and Telecommunications Trends
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• v.7 no.1
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• pp.38-46
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• 1992

음성통신에 있어 전화기의 주파수 특성은 음량과 함께 통화품질에 많은 영향을 미친다. 각 국에서는 자국의 통신실정에 맞는 주파수 특성을 규정하고 있지만, 다른 나라의 규정을 그대로 도입하는 것은 도리어 전화기의 품질 열화를 초래할 수 있다. 본 고에서는 전화통화에 있어 만족한 통화품질을 얻을 수 있는 바람직한 주파수 특성을 구하고자, 주파수 특성에 대하여 오피니언 평가 및 선호도 평가를 실시하고, 그 결과를 기본으로 최적 주파수 특성에 대해 검토하였다.

• The Journal of the Korea Contents Association
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• v.6 no.8
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• pp.20-29
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• 2006

This paper proposes a quality measurement model for video phone service over IP environment. Proposed model enhances conventional E-Model by using quality analysis and this model is suitable for ubiquitous environment. This research measures video phone quality by applying bust packet loss and recency effect. It uses delay and recency effect for compensating actual quality and recognized quality of user using NR and UR factor. Simulation results show that this model can provide more precise results than conventional model by considering recency effect of video phone service quality measurement model.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.221-224
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• 2002

VoIP 음성 통신 시스템에서 통화를 할 때, 네트워크 상황이 나빠짐에 따라 시간 지연, 패킷 손실, 지터 등의 QoS 파라미터에 의한 영향이 발생하므로 통화 품질이 떨어지게 된다 통화 품질을 개선하기 위해서는 통화 품질과 QoS 파라미터와의 관계를 명확히 파악하고 그에 대한 개선 방법을 연구해야 한다. 따라서 본 논문에서는 통화 품질과 QoS 파라미터와의 상관관계를 회귀 분석을 통해 도출해 내었다. 제시된 음질 평가 기준은 QoS 파라미터만을 가지고 음질을 예측하기 때문에 계산량이 매우 적으며, 음질 평가 수행 중에 음성 통신 시스템에 거의 영향을 미치지 않는다는 장점을 가지고 있다.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.69-70
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• 2001

음성 통신계를 통해서 전달되는 음성신호 품질의 좋고 나쁨을 수화자의 청각을 거친 반응(주관평가)에 의해 객관적으로 표현한 것을 통화품질이라 한다. 잠수기 어업 등과 같은 수중 활동에 사용할 무선수중전화기 시작품 설계와 최적의 통화품질 평가 방법 선점의 기초 자료로써 레저스포츠등에 인부 사용되고 있는 기존의 무전수중전화기로 수중 음성통신에서의 명료도와 단어 요해도를 측정하였다. (중략)

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1398-1400
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• 2011

2000년 초에 PC간 인터넷을 통한 음성통화를 시작으로 최근에는 스마트폰의 전용 애플리케이션까지 VoIP 기반의 음성통화 서비스가 발전해왔다. 이에 따라, VoIP를 통한 외부 공격 및 침입에 대한 사례가 발생되고 이를 해결하기 위한 보안 소프트웨어들이 나오기 시작하였다. 일반적으로 VoIP기반의 소프트웨어에 대한 품질 기준은 사용자의 통화품질이 최우선 이었다. 하지만, GS시험.인증 과정을 통해 VoIP 보안 소프트웨어가 통화품질에는 직접적인 영향을 미치지는 않지만 전체 운영 시스템에 미치는 영향을 확인하고, 시험 중 발생한 문제에 대한 해결 방안 제시를 통해 VoIP의 품질을 향상시킬 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1327-1332
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• 2015

In this paper, we studied several aspects that affect the quality of VoIP using WiFi network. It's clear that the background data traffic within an AP, the end-to-end delay and the traffic loss of TCP/IP network gives serious effects on the voice quality. A kind of access control for the VoIP connection within an AP should be done for the acceptable voice quality.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.3
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• pp.48-54
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• 2012

The quality of real-time voice communication over Internet Protocol networks based on telematics is affected by network impairments such as delays, jitters, and packet loss. To resolve this issue, this paper proposes a receiver-based enhancing method of VoIP speech quality. The proposed method enables users to deliver high-quality voice using playout control and signal reconstruction, which consists of concealment of lost packets, adaptive playout-buffer scheduling using active jitter estimation, and smooth interpolation between two signals in a transition region. The proposed algorithm achieves higher Perceptual Evaluation of Speech Quality (PESQ) values and low buffering delay than the reference algorithm.

• The Journal of the Acoustical Society of Korea
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• v.29 no.5
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• pp.347-353
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• 2010

In VoIP system, the speech quality is seriously degraded due to packet loss, and the degree of degradation by each packet loss depends on the characteristics of the corresponding packet. Therefore, it is possible to improve the speech quality of VoIP by selectively controlling the packet to be lost during transmission based on the expected degradation by the loss of each packet. In this paper, a new scheme to improve speech quality of DiffServ-based VoIP by assigning priority to each packet is proposed, and a method to determine the priority of each packet is developed. The performance of proposed method was measured in packet loss environment based on Gilbert model, and it was verified both objectively and subjectively that the speech quality is improved by the proposed method.