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Quality-based VoIP charging mechanism design from listening and identification test
정윤찬,J. William Atwood,남종호 한국인지및생물심리학회 2010 한국심리학회지 인지 및 생물 Vol.22 No.3
Providing quality-of service (QoS) guarantees in VoIP applications becomes more challenging in wireless and mobile networks. Then, one of the important issues is to find a mechanism that can probe to what degree the users are satisfied with their experiences and give them service quality guarantees with varying prices depending on the network performance they may experience. In the traditional telephone services, the issue of the quality-based accounting has been relegated to the margins of quality communications. Also existing studies to date rarely deal with quality-based VoIP accounting because it is very difficult to find a suitable VoIP accounting metric. In this paper, we use a methodology of listening and identifying word by word and derive a VoIP accounting metric. Using the accounting metric, we design a quality-based VoIP charging mechanism with a “no charging” window.
Securing RTP Packets Using Per-Packet Key Exchange for Real-Time Multimedia
정윤찬,Enrique Festijo,J. William Atwood 한국전자통신연구원 2013 ETRI Journal Vol.35 No.4
For secure multimedia communications, existing encryption techniques use an online session key for the key exchange, for which key size is limited to less than 10 digits to accommodate the latency condition caused by user devices only being able to handle low computational loads. This condition results in poor security of recorded encrypted data. In this letter, we propose a packet key scheme that encrypts real-time packets using a different key per packet for multimedia applications. Therefore, a key of a relatively small size can provide after-transmission confidentiality to data of a real-time session.
Multi-kilowatt Single-mode Ytterbium-doped Large-core Fiber Laser
정윤찬,Johan Nilsson,David N. Payne,Alexander J. Boyland,Jayanta K. Sahu,정승환 한국광학회 2009 Current Optics and Photonics Vol.13 No.4
We have demonstrated a highly efficient cladding-pumped ytterbium-doped fiber laser, generating >2.1 kW of continuous-wave output power at 1.1 μm with 74% slope efficiency with respect to launched pump power. The beam quality factor (M2) was better than 1.2. The maximum output power was only limited by available pump power, showing no evidence of roll-over even at the highest output power. We present data on how the beam quality depends on the fiber parameter, based on our current and past fiber laser developments. We also discuss the ultimate power-capability of our fiber in terms of thermal management, Raman nonlinear scattering, and material damage, and estimate it to 10 kW.
Impact of the Adaptive Packet Coding on Speech Quality in Wireless VoIP
정윤찬,Hans-Ju¨rgen Zepernick,J. William Atwood,Al Ann Ibanez 에스케이텔레콤 (주) 2010 Telecommunications Review Vol.20 No.3
The specific packet loss recovery coding used in a Voice over IP (VoIP) system can have a significant impact on the quality delivered to the receiver. We explore three types of basic packet coding used in managing Quality of Service (QoS). Taking into account the study results of them, we propose the quality packet coding methods which perform robust over wireless and mobile networks having much higher average packet loss rates than wired networks. Then we explore the issue of how to reduce network bandwidth necessary for support of the quality packet coding. In this paper,we propose the adaptive quality coding, which can not only improve the perceptual quality for VoIP services over wireless environments but also utilize a small amount of additional bandwidth. We claim that the adaptive operation of the quality packet encoding at the network layer in the sending host does not significantly increase the network throughput comparing with the nonadaptive operation of that. This idea is considered to be important because the efficient use of network bandwidth is essential for support of ever-growing demand in VoIP applications.
개에서 단극 심장 앞 흉부유도를 이용한 Holter monitoring의 임상적 적용 방법
정윤찬,방동하,김유석,황철용,윤화영 한국임상수의학회 2011 한국임상수의학회지 Vol.28 No.1
Holter monitoring has been recognized as an useful noninvasive instrument for monitoring the cardiac electrical activity over 24 to 48 hours. Because the surface electrocardiogram (ECG) is recorded only for several seconds to minutes, it often misses or underestimates the underlying arrhythmia. The surface ECG is also easily influenced by depolarization potentials from skeletal muscle by the movement of patient (especially muscle tremor). However,holter monitoring is less affected by such factors. There has been no precedential report in veterinary medicine applying digital holter monitor with unipolar precordial chest lead using 4 electrodes. This article describes its clinical indications,equipment and technical application method in dogs.
Quality-based Charging Mechanism Design for VoIP Test
정윤찬,Al Ann Ibanez 에스케이텔레콤 (주) 2011 Telecommunications Review Vol.21 No.5
Providing Quality-of Service (QoS) guarantees in VoIP applications becomes more challenging in wireless and mobile networks. One of the important issues is to find a mechanism that can probe to what degree the users are satisfied with their experiences and give them service quality guarantees with varying prices depending on the network performance they may experience. In this paper, we use a methodology of listening and identifying word-by-word in order to obtain the criterion metric, which enables users to identify whether they are satisfied with their experiences or not. Investigating the relationship between the gap ratio and PESQ MOS, we derive the charging ratio, which can be used as the proportion of quality-based prices to ''delivered packet amount''-based prices. Finally, we design the charging ratio model which can be a key component of quality-based VoIP charging mechanism.