• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.4
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• pp.1006-1025
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• 2012

Improving the quality of service in IP networks is a major challenge for real-time voice communications. In particular, packet arrival-delay variation, so-called "jitter," is one of the main factors that degrade the quality of voice in mobile devices with the voice-over Internet protocol (VoIP). To resolve this issue, a receiver-based enhanced timing recovery algorithm combined with active jitter estimation is proposed. The proposed algorithm copes with the effect of transmission jitter by expanding or compressing each packet according to the predicted network delay and variations. Additionally, the active network jitter estimation incorporates rapid detection of delay spikes and reacts to changes in network conditions. Extensive simulations have shown that the proposed algorithm delivers high voice quality by pursuing an optimal trade-off between average buffering delay and packet loss rate.

• Journal of Communications and Networks
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• v.17 no.5
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• pp.534-540
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• 2015

In this paper we propose an analytical model for jitter, wherein we implement the interrupted Poisson process (IPP) for incoming traffic. First, we obtain an analytical model for the jitter on one node with respect to the phase probabilities, traffic load, and tagged traffic share in the aggregate traffic flow. Then, we analyze N-node cases, and propose a model for end-to-end jitter. Our analysis leads to some fast-to-compute approximations that can be used for future network design or admission control. Finally, we validate our analytical results by comparing them with previous results for limit cases, as well as with event-driven simulations. We propose the use of our results as guidelines for jitter evaluation of real IP traffic.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.457-462
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• 2014

This letter proposes a low-jitter DLL-based clock generator with two negative feedback loops. The main negative feedback loops suppress the jitter of DLL. The additional negative feedback loops suppress the delay-time variance of each delay stages. Both two negative feedback loops in a DLL results in suppressing the jitter of clock signal further. Measurement results of the DLL-based clock generator with two negative feedback loops fabricated in a one-poly six-metal $0.18{\mu}m$ CMOS process show 5.127-ps rms jitter and 47.6-ps peak-to-peak jitter at 1 GHz.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.48-48
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• 2010

현재 포항가속기연구소의 선형가속기에서 운전되고 있는 모듈레이터는 클라이스트론의 펄스 전원을 공급하는 펄스 전원공급 장치로서 출력은 최대 400 kV, 500 A, $7.5\;{\mu}s$의 펄스를 S band 클라이스트론에 공급한다. 모듈레이터의 고전압펄스 약 40 kV을 스위칭 하기위하여 진공스위치인 싸이라트론 스위치를 사용하고 있다. 모듈레이터 시스템에서 Jitter 발생 요인을 살펴보면, 대부분 싸이라트론 스위치회로에서 발생된다. 싸이라트론이 유발시키는 Jitter는 약 10 ns 이하이므로 매우 적다고 할 수 있다. 스위치의 Jitter가 적음에도 불구하고 모듈레이터 시스템에서 Jitter가 크게 발생한다면, 싸이라트론의 음극(cathode)에서 양극(anode)으로 흐르는 전자빔을 제어하는 Control Grid(G1 & G2)의 pulse 전압의 Jitter가 크기 때문이다. 싸이라트론 Grid 2에 공급되는 pulse 전압의 Jitter를 줄이는 것은 필수적이라 하겠다. 진공스위치인 싸이라트론 Grid에 pulse 전압을 공급하는 싸이라트론 드라이버 시스템의 안정화가 중요하므로 시제품 설계시 안정성을 충분히 고려하였다. 본 발표에서는 시제품으로 제작한 Thyratron Drive System의 기능 및 측정결과에 대해서 기술하고자 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5541-5554
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• 2018

A voice is one of the most significant non-verbal elements for communication. Disorders in vocal organs, or habitual muscular setting for articulatory cause vocal disorders. Therefore, by analyzing the vocal disorders, it is possible to predicate vocal diseases. In this paper, a method of predicting vocal disorders using the jitter, shimmer, and harmonics-to-noise ratio (HNR) extracted from vocal records is proposed. In order to extract jitter, shimmer, and HNR, one-second's voice signals are recorded in 44.1khz. In an experiment, 151 voice records are collected. The collected data set is clustered using cobweb clustering method. 21 classes with 12 leaves are resulted from the data set. According to the semantics of jitter, shimmer, and HNR, the class whose centroid has lowest jitter and shimmer, and highest HNR becomes the normal vocal group. The risk of vocal disorders can be predicted by measuring the distance and direction between the centroids.

• Proceedings of the Korea Society of Design Studies Conference
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• 2003.05a
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• pp.30-31
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• 2003

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12C
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• pp.199-207
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• 2001

We propose an adaptive shaping controller equipped with the technologies of shaping and buffering VoIP packets arriving at the receiving end by the CAM-type controller. In order to conceal interarrival packet delay variation, the conventional jitter buffers force them to be too large, thereby causing the audio quality to suffer excessive delay. However, by using our proposed method, the delay caused by shaping operation dynamically increases or decreases on the level of jitter that exists with in the IP network. This makes the delay accommodates adaptively the network jitter condition. The less jitter network has the fewer delay the shaping controller requires for jitter elimination. And the CAM-type method generally makes the shaping operation faster and leads to processing packets in as little time as can. We analyse the packet loss and delay performance dependency on the average talk ratio and the number of jitter buffer entries in shaping controller. Surprising, we show that the average delay using our shaping controller is about 70msec. This performance is much better than with the delay equalization method which forces the receiving end to delay about 60msec.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.80-87
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• 2004

Active control of on-orbit spacecraft jitter is a significant problem for future spacecraft mission requiring stringent pointing performance. Jitter is major disturbance source degrading payload pointing performance. Both passive and active jitter isolation techniques have been studied during the last decade. We present active jitter isolation for a model device in this work. The device provides active control capability by 3 degree-of-freedom control of payload in feedback control strategy. Mathematical modeling of the device is pursued which is naturally used for a baseline controller design. Simulation results are used to validate the designed control law.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.3
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• pp.213-220
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• 2020

This paper proposes a method on the performance analysis of pulse repetition frequency jitter compensation for generating Doppler profile. Exact phase compensation of each pulse is required to obtain Doppler profiles under pulse repetition frequency jitter. Three parameters such as velocity, pulse repetition frequency, and carrier frequency are examined to cause errors when conducting the pulse repetition frequency jitter compensation, then assuming well-focused Doppler profiles reflect well-conducted pulse repetition frequency jitter compensation, the proposed method in this paper utilizes the contrast to measure how well Doppler profile is generated. These are validated by electromagnetic computation data and computer simulation. Then, it is concluded which parameter is important on the performance analysis of pulse repetition frequency jitter compensation by using the contrast.

• Journal of Astronomy and Space Sciences
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• v.30 no.3
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• pp.141-143
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• 2013

We propose jitter radiation and jitter self-Compton process in this work. We apply our model to the study of GRB prompt emission and GeV-emission. Our results can explain the multi-wavelength spectrum of GRB 100728A very well.