• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1549-1558
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• 2012

Location-aware system is utilized in various fields such as Logistics, Home Network, Healthcare, Military and Transportation systems. In this paper, we designed and implemented a Location-aware system based on IEEE 802.15.4a CSS (Chirp Spread Spectrum) technology in variable environment. The CSS is possible to precision location awareness using RF signal. According to experimental result, the implemented system has recognition error less than 0.5m within 20m radius in space.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.494-505
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• 1990

This paper reports on the development of a DPSK demodulator of DS spread spectrum communications that use one SAW convolver. The spreading code chip pattern is changed from bit to bit in data portion of packet. And code chip is PSK modulated. Compared with simulation, experiment shows that the DPSK signal spreaded can be demodulated by using only one SAW convolver. And the theoretical performance of this DPSK demudulator is equal to CSK demodulator wich uses two SAW convolvers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.475-484
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• 1990

This paper proposes a method for the implementation of a power line communication equipment using power line synchronization in a direct-sequence spread spectrum communication system. In order to implement a network using a power line as a transmission channel we have investigated the utilization of direct-sequence speread spctrum which gives such advantages as robustness against narrow-band interference and noise, and realization of multiple access. In a power line, however, complexity of synchronization makes it difficult to realize a multiple access and cost down and system simplification. The proposed technique of power line synchronization makes it possible to get cost down and system size small, and the realization of multiple communication can be achieved by the addition of address setting circuit.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.907-910
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• 2001

본 논문에서는 저작권자의 개인 ID 를 직접 행렬 대역확산(Direct Matrix-Spread Spectrum) 방식을 이용하여 워터마크 영상을 부호화한 후, 주파수 영역에서 원 영상에 삽입하고 검출하는 워터마킹 기법을 제안한다. 워터마크 영상은 시각적으로 인식 가능한 패턴(마크, 로고, 심볼, 인장 또는 서명)을 사용한다. 워터마크가 삽입된 영상의 화질저하를 추정하기 위해 PSNR 을 계산하고, 검출된 워터마크의 복원률을 구하여 외부공격에 대한 워터마크의 강인성을 확인한다. 여러 표준영상에 적용해 본 결과 워터마크가 삽입된 영상의 PSNR 은 93.2 dB 로 우수한 화질을 얻을 수 있었으며, JPEG 손실 압축에서는 83.6 % 이상의 워터마크 복원률을 얻을 수 있었고 영상변형 및 잡음하에서도 효과적인 워터마크 검출 능력을 보였다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.2
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• pp.116-123
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• 2005

Chirp spread spectrum method using both time and frequency component is fit to time varying channel such as powerline channel. The used chirp symbol based on the CEBus standard is the unit symbol which sweeps from 100kHz to 380kHz over a 25㎲. To evaluate the performance of between Chirp-SS and DSSS, we measured the bit error rate under Gaussian channel. Simulation result is shown that Chirp-SS has a about 3[dB] gain of SNR than DSSS. To verify the performance of implemented modem, it is made up the powerline channel environment. After adding several noises to it, we examined the receiving status of modem. The implemented modem is able to receive the signal over the powerline channel with having several noises and capacitive loads.

• Electronics and Telecommunications Trends
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• v.16 no.5 s.71
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• pp.101-112
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• 2001

여러 가지 확산방식 가운데 2.4GHz 대역에서 블루투스, 무선 LAN 등에 적용되고 있는 FHSS(Frequency Hopping Spread Spectrum) 방식을 사용하는 무선기기들에 대하여 미국과 유럽 그리고 일본에서 정하고 있는 기술기준 또는 표준에 관하여 개괄적으로 살펴보았다. 지역별로 정하고 있는 기술기준과 연계하여 각각의 기술기준 또는 표준의 항목들이 의미하는 바를 측정의 관점에서 기술하였으며, 다양한 측정 방법들이 갖는 기술적인 내용에 대하여도 포괄적으로 분석하였다. 마지막으로 최근 국내에서도 FHSS 방식을 사용하는 무선기기들에 대한 기술기준이 개정 고시됨에 따라 국내의 기술기준의 개정 배경과 의미를 외국 기술기준의 내용과 비교하여 설명하였으며, 그 측정 방법에 내포된 의미와 차이점들을 분석하였다.

• Management & Information Systems Review
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• v.3
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• pp.201-214
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• 1999

Adaptive correlator receiver with neural network based on complex multilayer perceptron is persented for suppressing interference of narrow-band of direct spread spectrum communication systems. Recursive least square algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise and transmission power, computer simulation results show that bit error ratio of adaptive correlator using neural network improved that of adative transversal filter of direct sequence spread spectrum considering of jamming and narrow-band interference. Bit error ratio of adaptive correlator with neural network is reduced about 10-1 than that of adaptive transversal filter where interference versus signal ratio is 5dB.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.3
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• pp.10-17
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• 1996

The performance of tau-dither loop (TDL) is evaluated for a direct-sequence spread-spectrum system in a multipath fading channel. The multipath fading channel is modeled as a two-ray rayleight fading channel. The code tracking perfomrance of TDL is analyzed in terms of tracking jitter and mean-tiem-to-lose-lick (MTLL). The tracking jitter performance is degraded while MTLL perfomrance is improved with increasing discriminator offset and decreasing power ratio of main to second paths. It is shown that for a large bit SNR, the effect of multipath fading becomes more significant. And it is also shown that tracking jitter and MTLL performance is less sensitive to delay spacing and discriminator offset for a small bit SNR than for a large bit SNR.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.465-467
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• 1999

The data transmission system in MAGLEV is required a high quality and high speed for a train safety and reliability driving. In the transmission channel between a vehicle and a ground-site, Gaussian noise is negligible, but impulse noise from the chopper controlled propulsoin unit and the Power supplying device is very severe. The transmission channel must be protected from these noise. In this paper, we propose a DSSS (direct-sequence spread spectrum) modulation as a new data transmission technique in the railway and analyze this data transmission characteristics.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.162-164
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• 2018

스위칭 주파수의 대역 확산 (Spread Spectrum) 기법은 전력 변환 장치의 전자 방해 잡음 (Electromagnetic Interference; EMI)를 줄일 수 있다. 하지만 공진형 컨버터는 스위칭 주파수 가변을 통해 출력 전압을 제어하기 때문에 스위칭 주파수의 대역 확산 기법을 적용하게 되면 출력 전압이 크게 흔들리게 된다. 본 논문은 LLC 공진형 컨버터에 대역 확산 기법을 사용함과 동시에 확산된 스위칭 주파수 대역의 위상 제어를 통해 출력 전압을 제어하는 방법을 제시하고자 한다. 제안하는 출력 전압 제어 성능 향상 및 전자방해잡음 감소 성능은 500 W 프로토타입 컨버터를 사용하여 검증하고자 한다.