• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.11
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• pp.14-18
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• 2010

We propose a performance analysis of code division multiple access systems based on the combination of M-ary and pseudo-noise spreading. In spite of the total bandwidth expansion being equal, there is a difference in the system performance by the combination of M-ary and pseudo-noise spreading. The proposed analysis uses each bandwidth expansion, caused by M-ary and pseudo-noise spreading, rather than the total bandwidth expansion. If the signal to interference plus noise ratio becomes high, it is more effective to reduce biterror rate by bandwidth expansion of M-ary modulation rather than that of pseudo-noise spreading. Since the proposed analysis reflects the effect of the M-ary modulation, the bit error rate from the proposed analysis is closer to the results of the simulation than from the conventional analysis.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.190-196
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• 2011

Bandwidth extension is a technique to improve speech quality and intelligibility, extending from 300-3400 Hz narrowband speech to 50-7000 Hz wideband speech. This paper designs an artificial bandwidth extension (ABE) module embedded in the AMR (adaptive multi-rate) decoder, reducing LPC/LSP analysis and algorithm delay of the ABE module. We also introduce a fast search codebook mapping method for ABE, and design a low power BWE technique based on the AMR decoder. The proposed ABE method reduces the computational complexity and the algorithm delay, respectively, by 28 % and 20 msec, compared to the traditional DTE (decode then extend) method. We also introduce a weighted classified codebook mapping method for constructing the spectral envelope of the wideband speech signal.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2021.06a
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• pp.63-64
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• 2021

본 논문은 wavenet을 이용하여 음성 신호의 대역폭을 확장하는 새로운 모델을 제안한다. 기존의 대역폭 확장은 주로 주파수 영역에서 진행되며, 확장 대역의 주파수 크기는 높은 성능으로 복원하지만 위상 정보를 정확히 복원할 수 없다는 문제점을 가진다. 이를 해결하기 위해 wavenet 모델을 기반으로 시간 영역에서 저대역과 고대역의 상관관계를 이용하여 고대역 성분을 생성하도록 한다. 제안하는 방법은 모든 동작을 시간 영역에서 수행하며, 제안 방법으로 생성한 고대역 성분이 원음의 고대역 성분과 유사한 것을 확인하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.265-267
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• 2001

본 논문에서는 QoS 멀티캐스트를 지원하기 위한 대역폭 브로커에 대하여 논한다. 현재 인터넷에서 QoS를 확장성있게 지원하기 위한 기술로 DiffServ가 대표적으로 적용되고 있으며, 해당 기술에서 특정 DiffServ 도메인내의 대역폭관리와 DiffServ 도메인간의 동적인 대역폭 관리는 대역폭 브로커라는 모듈에 의해서 수행된다. 본 논문에서는 멀티캐스트 라우터와의 연동기능을 기반으로하여, 다수의 사용자에게 QoS를 만족시킬수 있는 멀티캐스트 트래픽 전송을 지원하는 대역폭 브로커에 대하여 논한다. 해당 대역폭 브로커는 멀티캐스트 그룹내의 사용자의 가입/탈퇴에 따라 효과적으로 대역폭을 관리할 수 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.511-518
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• 2006

In this paper, a small RFID tag antenna in UHF band which has bandwidth-enhanced characteristic is proposed. The shape of the proposed antenna is a meander antenna to have size-reduced characteristic, and it consists of two radiators which make dual resonance in adjacent frequency to enhance bandwidth. By adjusting length and location of each radiator, the proposed antenna can make dual resonance at arbitrary location on the Smith chart, which is able to make impedance matching with RFID tag chip in wide frequency range. And it is apparent that the proposed antenna can have bandwidth-enhanced characteristic according to the simulated and measured results.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.470-472
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• 2000

본 논문은 Layered Transmission(LT)기법의 단점인 세밀하지 못한(coarse-grained) QoS 확장성을 보완하기 위해서 계층 단위로 세션을 떠나기 이전에 각 계층 내에서 프레임을 생략하는 기법을 제안한다. 이 기법은 기존의 LT 기법보다 네트워크 상태 변화에 따라서 좀 더 세밀한 QoS 확장성을 제공해 준다. 따라서 네트워크 대역폭의 활용도를 최대화하고 패킷 손실을 최소화할 수 있다. 또 사용 가능한 네트워크 대역폭을 최대한 활용함으로써 사용자들에게 최적의 서비스를 제공해 준다.

• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.70-77
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• 2017

Bandwidth extension is a technique to improve speech quality, intelligibility and naturalness, extending from the 300 ~ 3,400 Hz narrowband speech to the 50 ~ 7,000 Hz wideband speech. In this paper, an Artificial Bandwidth Extension (ABE) module embedded in the Opus audio decoder is designed using the information of narrowband speech to reduce the computational complexity of LPC (Linear Prediction Coding) and LSF (Line Spectral Frequencies) analysis and the algorithm delay of the ABE module. We proposed a spectral envelope extension method using DBN (Deep Belief Network), one of deep learning techniques, and the proposed scheme produces better extended spectrum than the traditional codebook mapping method.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.2
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• pp.177-187
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• 2000

In the past several years, many systems which adopted ring topology with high-speed unidirectional point-to-point links have emerged to overcome the limit of bus for interconnection network of clustered multiprocessor system. However, rapid increase of processor speed and performance improvement of local bus and memory system limit scalability of system with point-to-point link of standard bandwidth. Therefore, necessity to extend bandwidth is emphasized. In this paper, we adopt PANDA system as base model, which is clustering-based multiprocessor system. By simulating a model adopting commercial processor and local bus specification, we show that point-to-point link is bottleneck of system performance, and bandwidth expansion by more than 200% is needed. To expand bandwidth of interconnection network, it needs excessive design cost and time to develop new point-to-point link with doubled bandwidth. As an alternative to double bandwidth, we propose several ways to implement dual ring -simple dual ring, transaction-separated dual ring, direction-separated dual ring- by using off-the-shelf point-to-point links with IEEE standard bandwidth. We analyze pros. and cons. of each model compared with doubled-bandwidth single ring by simulation.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.112-114
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• 2004

최근에 널리 사용되고 있는 IEEE 802.l1b의 QoS보장은 중요한 기술적 이슈가 되고 있다. IEEE 802.l1b의 QoS를 보장하기 위한 정책을 효율적으로 수립하기 위해서는 현재 채널에서의 사용 가능한 대역폭을 예측할 수 있어야 한다. 본 논문은 기존에 제시 되었던 IEEE 802.l1b의 채 널 saturation 대역폭 모델을 확장하여 채널 상태의 모니터링을 기반으로 한 현재 의 채널에서 사용 가능한 대역폭의 예측 모델을 제안한다. 또한 실제 무선 환경을 구현하여 실험한 결과와 제안한 모델에서의 결과 비교를 통해 제안한 모델이 채널의 가용 대역폭을 효과적으로 예측할 수 있음을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.556-561
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• 2006

In this paper, a frequency reconfigurable slot antenna which has a bandwidth-enhanced characteristic is proposed. The proposed antenna consists of two parts; the wide slot and the narrow slot, to increase the bandwidth of the antenna and have the frequency reconfigurable characteristic. The wide slot has triangular shape and makes the bandwidth increased, and the narrow slot can mount PIN diodes. By changing on/off state of PIN diodes, the total length of the slot is changed. From this characteristic, the proposed antenna can finally control the center frequency and minimize variation of the impedance matching.