• 한국통신학회논문지
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• 제21권7호
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• pp.1803-1813
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• 1996

This paper describes an automatic threshold decision using a maximum mismatched correlation value in the direct sequence spread spectrum (DS-SS) system. For received PN codes with different single-to-noise ratio (SNR), this scheme is able to detect a desired threshold value in the search mode, i.e. a maximum mismstched correlation value, so that value is utilized as a threshold for the verification mode. Performance of the proposed scheme in both the additive white gaussian noise (AWGN) and frequency-selective Rayleigh fading channels is analyzed through the Monte Carlo simulation. And hardware implementation of this scheme using a DSP processor is demonstrated. The proposed acquisition shceme is compared to the conventional constant threshold (CT) scheme, and significant improvement of performance is shown. Analysis of system performance in the verification mode is presented, and key quantities such as the false alarm probability and the detection probability are derived in a AWGN channel.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 G
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• pp.2427-2429
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• 1998

Digital watermarking is the techinque which embeds the invisible signal into multimedia data such as audio, video, images, for copyright protection, including owner identification and copy control information. This paper proposes a new watermark embedding and extraction technique by extending the direct sequence spread spectrum technique. The proposed technique approximates the frequency component of pixels in spatial domain by using Laplacian mask and adaptively embeds the watermark considering the HVS to reduce the degradation of Image. In watermark extraction process, the proposed technique strengthens the high frequency components of image and extracts the watermark by demodulation. All this processes are performed in spatial domain to reduce the processing time.

• 전자통신동향분석
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• 제16권6호통권72호
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• pp.117-125
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• 2001

본 고에서는 최근 무선데이터 통신시스템용으로 2.4GHz 대역에서 블루투스 등 새로운 통신기기가 출현함에 따라서 이러한 기기에서 사용되는 여러 확산방식 중 직접열확산방식을 중심으로 하여 국내의 기술기준에 근거한 일본, 미국, 유럽의 측정방법에 대하여 검토하였다. 이러한 검토를 통하여 다양한 측정 방법들이 갖는 특징과 차이점들을 분석하여 국내에 적용할 수 있는지를 검토하고자 한다. 그리고 점유주파수대역폭, 주파수 허용편차, 공중선전력, 불요발사 등의 세부적인 항목을 함께 다루며, 각각의 측정 항목에 관한 구체적인 방법과 절차를 살펴볼 것이다.

• 산업경영시스템학회지
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• 제28권3호
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• pp.115-120
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• 2005

In this paper, we propose a personal-computer-based wireless data access system, which use DS/SS(Direct Sequence Spread Spectrum) method and the ISM band of 2.44GHz radio frequency. By applying hi-directional transmission between wireless handy terminals and PCs or servers, it can be easily connected with any kinds of database systems such as Oracle, MS-SQL and MS-ACCESS. Therefore, it could be economically adopted as peripheral equipments for ERP or SCM systems.

• Journal of Communications and Networks
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• 제7권1호
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• pp.36-44
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• 2005

In this paper, we present a retransmission power adjustment (RPA) scheme for DS/SSMA ALOHA packet radio systems with packet combining. In the proposed RPA scheme, retransmission power is adjusted in such a way that the erroneously-received packet can be recovered with a minimized interference to other user packets. We analyze the performance of the system with the RPA by employing the equilibrium point analysis (EPA), and confirm that the results obtained from the EPA are very close to the simulation results in low power cases. Simulation results demonstrate that the RPA scheme brings forth performance gain in the throughput and the average delay while saving a significant amount of transmission power. We also investigate the stability of the system from the EPA results, and conclude that the system becomes stable as the offered load increases or the level of retransmission power decreases.

• 한국전자파학회논문지
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• 제9권1호
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• pp.98-107
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• 1998

FM-DS /SS 시스댐 구현을 위하여, 주입되는 신호에 동기하는 주입형 SO (Synchronous Oscillator)에 대하 여 해석하였다. 송신부에서는 FM의 RF 출력 신호와 DS /SS(Direct Sequence /Spread Spectrum)을 이용하 여 FM-DS /SS 변조 방식을 채택하였으며, 수신부에서는,SO를 수신부의 PN(Pusudo Noise) 클럭 동기를 위한 슬라이딩 상관기로 사용하여 FM-DS/SS의 복조를 위한 동기부로 이용하였다. 그 결과 수신주파수가 도플러와 같은 현상에서도 안정된 동기성능을 유지하였으며, FM-DS /SS의 시스템에 적용하여 PN 동기 및 동기 특성 을 입증하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.539-542
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• 2005

본 논문에서는 900MHz의 ISM대역에서 사용가능한 통신방식 중 직접확산방식의 무선데이터 송수신 시스템을 제안${\cdot}$구현하였다. 특히 송수신기 간에 양방향 통신이 가능하도록 설계함으로써 900MHz 대역의 RF-ID 시스템과 같은 능동형 시스템으로의 확장이 가능하도록 하였다.

• 한국통신학회논문지
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• 제16권9호
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• pp.838-849
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• 1991

본 논문에서는 가우스 잡음과 임펄스 잡음이 혼합된 잡음 환경하에. 비선택적 페이닝 채널에서 PSK 변조한 DS/SSMA 시스템의 성능을 분석하기 위하여, 특정함수 방법을 이용하여 시스템의 평균 효율에 대한 식을 유도한 후 계산된 결과를 통해 시스템의 성능을 분석하였다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제15권1호
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• pp.53-59
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• 2015

This paper proposes a novel method for acoustically and wirelessly transmitting data underwater with a high transmission rate. The method uses the most promising physical layer and multiple access technique (i.e., the code division multiple channel access technique) to divide the channel into subchannels. Data is transmitted through these subchannels. The codes are pseudo-random noise (PN) sequences. In the spread-spectrum technique, a signal such as electrical, electromagnetic, acoustic signal generated in a particular bandwidth is deliberately spread in the frequency domain, which results in a signal with a wider bandwidth. This paper reviews the possibility of application of the direct-sequence code division multiple access (DS-CDMA) technique in an underwater system using MATLAB. As the result of our review, we recognize that the DS-CDMA technique can be applied to underwater environments.

• 한국군사과학기술학회지
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• 제19권6호
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• pp.762-768
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• 2016

In this paper, a method for generating ranging signal to reduce the effects of interference and overcome intentional jamming is proposed in slow frequency hopping(SFH) communication system. A terminal uses ranging signal for initial Up-link synchronization in the frequency hopping communication systems using multi-terminal. However, ranging signal generated by unsynchronized terminal acts as an interference signal to another terminal. Therefore, we propose the design of the ranging signal with PN sequence in order to minimize the affection to the other terminal and simulated its performance. From the simulated result, we confirm synchronization performance.