• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.9-12
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• 1999

전력선은 백색 가우시안 배경 잡음뿐 아니라 임펄스 잡음, 고조파 잡음 등의 비 가우시안 잡음들로 인해 통신 채널로서 열악한 전송 특성을 나타낸다. 또한 좁은 가용 대역폭으로 인해, 광대역 특성이 요구되는 DS-CDMA 방식과 같은 대역 확산 시스템의 적용에 한계가 있다. 본 연구에서는 차세대 고속이동통신을 위한 다원접속/변조방식인 멀티코드 (multi-code) CDMA 방식과 이에 길쌈 부호와 인터리빙 등의 부호화 기능을 더한 시스템을 전력선 통신 시스템에 적용하고, 모의실험을 통해 전력선 채널의 비 가우시안 잡음의 영향을 매우 효과적으로 보상할 수 있음을 확인하였다.

• Proceedings of the KIEE Conference
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• summer
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• pp.325-326
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• 2004

전력선통신(PLC: Power Line Communication)은 기존의 전기선을 이용하여 별도의 전용선 설치 없이 통신이 가능한 기술로서 효율적인 PLC 통신을 위해서는 가장 기본적인 기저대역의 송, 수신부상 의 원활한 데이터 전송이 이루어져야 한다. 본 논문에서는 확산대역방식의 PLC통신시스템의 수신부의 핵심모듈인 정합필터를 HDL(hardware description language)을 이용한 디지털 하드웨어인 에 위한 디지털 하드웨어인 FPGA(Field Programmable Gate Array)클 이용하여 구현하였다. 즉, 본 논문에서는 BPSK(Binary Phase Shift Keying) 변조 및 256칩 확산코드를 이용한 확산변조파형에 대한 디지털 정합필터를 FPGA로 구현하고 상관특성을 확인함으로서 모의실험상의 파형과 구현된 하드웨어상의 상관파형이 일치함을 확인하였다.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.137-140
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• 2004

RFID는 각종 서비스 산업은 물론 물류, 산업 현장, 제조 공장과 물품의 흐름이 있는 곳이면 어디에서나 적용이 가능하여 사회 여러 분야로부터 큰 관심을 받고 있다. 하지만 현재 900Mhz 대역의 RFID에서 사용하는 ISO18000-6의 프로토콜에서는 에러검출을 위한 CRC16만을 사용하여, 에러정정능력을 갖추지 못해 그 신뢰성이 떨어질 것으로 여겨진다. 본 논문에서는 이러한 RFID 시스템의 신뢰성 향상을 위해 Reader에서 Tag로의 Command data 전송 시에 대역확산방식과 콘벌루션부호를 적용하여 시스템의 신뢰성 향상을 목적으로 하며, 이러한 방식을 적용했을 때와 적용하지 않았을 때의 에러 율을 측정 비교하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.729-739
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• 1994

In a centralized spread-spectrum packet radio network, a random assignment -transmitter-based spreading code protocol(RA-T) is proposed which permits the contention mode only in the trasmission of a preamble while avoiding collision during the data packet transmission by assigning near-orthogonal spreading codes to each user. Compared to the conventional transmitter-based code scheme, this scheme allows reduction in receiver complexity when only a small number of distinct spreading codes are employed for the preamble transmission. Throughout theoretical and simulation results, it is shown that the use of the RA-T scheme with just two or three distinct codes for the preamble packet achieves most of the performance gain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.737-748
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• 2005

Two flexible admission control schemes for integrated voice and stream-type data services are proposed in DS-CDMA systems. Most Previous studies on admission control have focused on integration of short, bursty Packet-type data services and conventional voice services. However, stream-type data services with a relatively long service holding time are expected to be a considerable portion of data traffic in future generation cellular systems. Scheme I is a basic scheme that accommodates both voice and data services with full bandwidth. However, voice services are given priority over data services using the duration difference between the holding times for these services. Scheme ll uses a different method to efficiently give priority to voice services over stream-type data services. An additional interference margin for voice services is provided by suppressing interference from stream-type data services according to voice access requests and a varying interference status. Performance of the two schemes is evaluated by developing Markovian models. Numerical results show that the voice capacity is highly sensitive to the service holding time of data services while the performance measures of data services are not highly sensitive. Scheme H is a significant improvement over Scheme I for accommodating voice and stream-type data services

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.440-447
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• 2007

The switched diversity, although its performance is a little inferior to the selection diversity, is widely used due to its advantage that only one RF circuit is required for its operation without respect to the number of antennas in use. In this paper, we propose an application of the antenna switched diversity to a spread spectrum system with adaptive modulation and derived the optimal antenna switching threshold to maximize the average transmission bit rate. We also compared the performances of the proposed system with those of the two cases using a single antenna and the selection diversity with two antennas in terms of the average number of bits per symbol(BPS), the probability of no transmission, and the average BER. The performance analysis shows that, if the number of paths in a multipath channel environment increases, the performance of the proposed scheme becomes closer to that of the selection diversity based system in terms of the average BPS. Furthermore, the proposed scheme produces as almost high the probability of no transmission as the selection diversity based system for the case of low average SNR, although the former yields a little higher probability of no transmission than the latter fer the case of high average SNR.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.182-188
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• 2018

In order to increase the robustness of the uplink for UAS(Unmanned Aerial System), we propose a jamming signal rejection algorithm. In the UAS datalink system, DSSS (direct sequence spread spectrum) is used to reduce the radio noise or jamming signal. In general, jamming signals below the spreading gain are recoverable but the signals beyond the spreading gain can not be recovered. In this paper, these jamming signals beyond spreading gain are detected using the threshold detector in the spectrum area then, generate the estimated signals from the sine wave generator. Finally, we obtain the desired signal to remove jamming signals from the received signals. The proposed scheme can eliminate jamming signals while minimizing the hardware complexity and the original signal loss.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.437-439
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• 2003

본 논문에서는 대역확산방식을 응용한 새로운 워터마킹 방법에 대해서 설명하고, 이를 이용하여 semi-fingerprinting을 구현할 수 있는 데이터 구조에 대해서 기술하였다. 본 논문은 저작권 보호에 주초점이 맞추어져 있는 워터마크 기술을 실질적으로 필요한 fingerprinting분야에 적용함으로써, 그 동안 학문연구에 그치고 있었던 워터마크 기술을 산업적 응용에까지 확대시키는데 큰 기여를 할 것으로 기대된다. 본 논문에서 제안한 워터마킹 방법은 난수이동(random number shift)방법을 이용하여 데이터 삽입량을 증가시켰다. 또한, semi-fingerprinting에 적용하기 위해 일본 내에서 진행중인 cIDf의 지침에 기반 하여 워터마크를 구성하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.128-133
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• 2010

We investigate the optimal chip rate of power or rate adapted direct-sequence code division multiple access (DS/CDMA) communication systems in Nakagami fading channels. We find that the optimal chip rate that maximizes the spectral efficiency depends upon both the channel parameters, such as multipath intensity profile (MIP) and line-of-sight (LOS) component, and the adaptation scheme itself. With the rate adaptation, the optimal chip rate is less than $1/T_m$, irrespective of the channel parameters, where $1/T_m$ is multipath delay spread. This indicates that with the rate adaptation, correlation receiver achieves higher spectral efficiency than RAKE receiver. With the power adaptation, however, the optimal chip rate and the corresponding number of tabs in RAKE receiver are sensitive to MIP and LOS component.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.39-44
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• 2010

In this paper, we derive the channel capacity in order to transmit an additional data by using digital watermarking method in generalized-K fading channel. Spread spectrum watermarking is one of the digital watermarking methods which is the most promising technique due to it's very robustness to the channel noise and easy achieving of the signal detection by correlators at the receiver. It is important to analyze the channel capacity to transmit an additional data through wireless channel because the transmitted data would be affected by the channel fading effects. From the results, we confirm that the channel capacity of the SSW system can be determined by the HWR, WNR, PN length and host sampling frequency. Also, we verified that the level of HWR and WNR can be determined by the derived capacity formula. The results of this paper can be applied to general spread spectrum watermarking system.