• 산업기술연구
• /
• 제24권B호
• /
• pp.177-186
• /
• 2004

The main bottleneck for a VOD system is bandwidth of storage or network I/O due to the high bandwidth requirements and long-lived nature of digital video. Patching is one of the most efficient techniques to overcome the bottleneck of the VOD system through the use of multicast scheme. In this paper, we propose a new patching scheme, P2P proxy patching, for improving the typical patching technique by jointly using the proxy prefix caching scheme and the P2P proxy. In our proposed scheme, each client play a role in a proxy for multicasting a regular stream to other clients that request the same stream. Due the use of the P2P proxy and the prefix caching, the server bandwidth is required significantly less than that of the typical patching technique. In the performance study, we show that our patching scheme can reduce the server bandwidth requirements compared with the existing patching techniques.

• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2000년도 춘계종합학술대회
• /
• pp.489-492
• /
• 2000

This paper describes a new transient voltage suppressor(TVS) with a low insertion loss and a very wide frequency bandwidth to protect antenna circuit from transient voltages. Conventional protection devices have some problems such as low frequency bandwidth and high insertion loss. In order to improve these limitations, a coaxal type TVS, which consists of a gas tube is developed. The performance of the proposed transient voltage suppressor is tested by using a combination surge generator specified in IEC 61000-4-5 standard and by using a network analyzer of 40 MHz ∼ 5GHz bandwidth. From the experimental results, it is confirmed that the proposed TVS has an enough protection performance in low insertion loss and in wide frequency bandwidth

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.138-141
• /
• 2001

In this paper, a VBF(variable bandwidth filter) is suggested and analyzed in time-frequency domain. There are four kinds of VBF, which are low-pass VBF, high-pass VBF, band-pass VBF and band-stop VBF. The proposed VBF can extract the components of signals within variable instantaneous bandwidth at a specific time instant. Instantaneous bandwidth is estimated in time-frequency domain. The VBF is represented by rational form in extended Fourier frequency domain.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2013년도 춘계학술대회
• /
• pp.747-748
• /
• 2013

본 논문에서는 XGPON1 (10-Gbps-capable passive optical network stage 1) 시스템에 사용 가능한 새로운 동적 polling 방법을 제안한다. XGPON1 시스템은 상향 2.5 Gbps, 하향 10 Gbps 속도를 지원한다. XGPON1 시스템에서는 polling 빈도가 높으면 동적대역할당의 효율이 증가하지만 상향대역폭이 낭비되는 문제가 발생된다. 제안된 polling 방법은 polling에 사용되는 상향 대역폭 낭비를 줄이고 동시에 polling 횟수를 효율적으로 향상시킨다.

• 한국전기전자재료학회논문지
• /
• 제16권10호
• /
• pp.887-891
• /
• 2003

In this paper, two filters with center frequency of 19.58MHz were cascaded and its bandwidth characteristics were investigated with the variations of coupling capacitance for intermediate frequency (IF) bandpass filter application. The cascaded filter showed the higher stop region, reduction of spurious response and increase of selectivity. With the increase of coupling capacitance, insertion loss was increased but spurious response reduced. The cascaded filter with coupling capacitance of 15pF showed insertion loss of 5.643dB, 3dB bandwidth of 55.089kHz and 20dB bandwidth of 83.608kHz, respectively.

• Journal of the Optical Society of Korea
• /
• 제18권1호
• /
• pp.15-22
• /
• 2014

We present a novel bandwidth measurement scheme for multimode optical fibers. Amplified spontaneous emission (ASE) radiation was utilized for a source of intrinsically modulated light with a wide modulation bandwidth. In our measurement scheme, the continuous-wave (CW) ASE light that passed through a multimode fiber (MMF) under test was analyzed by the fourth-order power with a high-speed photodetector and an electric spectrum analyzer. The modulation transfer function of the multimode fiber could be directly measured with the photoelectric spectra in the modulation frequency domain. The measurement result of our method was experimentally compared to that of the conventional measurement scheme based on the impulse response measurement. It has been found that our scheme provides a stable measurement means of MMF characterization that is suitable for the field testing due to the simplicity of the system.

• 한국통신학회논문지
• /
• 제25권6A호
• /
• pp.910-917
• /
• 2000

Because the random early detection(RED) algorithm deals all flows with the same best-effort traffic characteristic, it can not correctly control the output link bandwidth for the flows with different traffic characteristics. To remedy this problem, several per-flow algorithms have been proposed. In this paper, we propose a new per-flow type Fair Droptail algorithm which can fairly allocate bandwidth among flows over a shared output link. By evenly allocating buffers per flow, the Fair Droptail can restrict a flow not to use more bandwidth than others. In addition, it can be simply implemented even if it employs the per-flow state mechanism, because the Fair Droptail only keeps each information of flow in active state.

• 한국정보과학회논문지:정보통신
• /
• 제37권6호
• /
• pp.415-419
• /
• 2010

본 논문에서는 이동 셀룰러 네트워크 환경에서 한정된 자원인 무선대역폭을 효율적으로 사용하기 위해 게임이론을 이용한 대역폭 예약 기법을 제안하였다. 제안된 기법에서는 게임 이론의 협상 해법 중 대표적인 NBS 기법을 이용하여 전체 시스템의 효용을 극대화하는 최적의 대역폭 대여량과 예약량을 계산한다. 성능평가 결과 제안된 기법이 다양한 네트워크의 상황에 탄력적으로 대응할 수 있었기에 기존에 제안된 기법에 비해 뛰어난 성능을 보임을 확인할 수 있었다.

• Current Optics and Photonics
• /
• 제3권5호
• /
• pp.438-444
• /
• 2019

In this theoretical study, a line-defect photonic-crystal waveguide hosted in an annular photonic crystal was demonstrated to provide high-performance slow light with a wide band, low group-velocity dispersion, and a large normalized delay-bandwidth product. Combined with structural-parameter optimization and selective optofluid injection, the normalized delay-bandwidth product could be enhanced to a large value of 0.502 with a wide bandwidth of 58.4 nm in the optical-communication window, for a silicon-on-insulator structure. In addition, the group-velocity dispersion is on the order of $10^5$ ($ps^2/km$) in the slow-light region, which could be neglected while keeping the signal transmission unchanged.

• Journal of Communications and Networks
• /
• 제13권6호
• /
• pp.664-677
• /
• 2011

In order to control interference and improve spectrum efficiency in the femtocell and macrocell overlaid system (FMOS), we propose a joint frequency bandwidth dynamic division, clustering and power control algorithm (JFCPA) for orthogonal-frequency-division-multiple access-based downlink FMOS. The overall system bandwidth is divided into three bands, and the macro-cellular coverage is divided into two areas according to the intensity of the interference from the macro base station to the femtocells, which are dynamically determined by using the JFCPA. A cluster is taken as the unit for frequency reuse among femtocells. We map the problem of clustering to the MAX k-CUT problem with the aim of eliminating the inter-femtocell collision interference, which is solved by a graph-based heuristic algorithm. Frequency bandwidth sharing or splitting between the femtocell tier and the macrocell tier is determined by a step-migration-algorithm-based power control. Simulations conducted to demonstrate the effectiveness of our proposed algorithm showed the frequency-reuse probability of the FMOS reuse band above 97.6% and at least 70% of the frequency bandwidth available for the macrocell tier, which means that the co-tier and the cross-tier interference were effectively controlled. Thus, high spectrum efficiency was achieved. The simulation results also clarified that the planning of frequency resource allocation in FMOS should take into account both the spatial density of femtocells and the interference suffered by them. Statistical results from our simulations also provide guidelines for actual FMOS planning.