• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.249-252
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• 2001

TCM(Trellis Coded Modulation) has soft decision scheme so that BM(Branch Metric) calculates the ED(Euclidean Distance) between the received signal and each code words in signal space. For computing the ED, square and square root computations increase the hardware complexity. Some simplified method is known for convolutional codes with QPSK(Quadrature Phase Shift Keying), PSK(Phase Shift Keying) modulation. But it is not acceptable for QAM (Quadrature Amplitude Modulation)-TCM scheme. In this paper, we suggest that two modified BM computation methods, which is applicable for QAM-TCM. By comparative study, we also assessed two proposed method in the case of hardware complexity and BER (Bit Error Rate) performance.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.50-54
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• 2007

현재 국내에서 ITS(Intelligent Transport Systems) 통신방식으로 이 용되고 있는 DSRC 방식은 TTA(한국정보통신기술협회)의 기술표준으로서 대전시,전주시에 적용되어 BIS(Bus Information Service)에 이용되고 있고,최근 고속도로 ETCS(Electronic Toll Collection System)가 DSRC방식으로 전국고속도로 Tollgate 에서 2007년 연말에 개통될 예정이다. DSRC 방식은 2000년에 TTA(한국정보통신기술협회)에서 기술표준이 제정되어 현재 1Mbps 의 Data 용량을 가진다. DSRC 방식의 물리링크 변조방식은 ASK(Amplitude Shift Keying)로 ITS 확장 서비스 적용을 위해 변조방식을 QPSK(Quadrature Phase Shift Keying )로 개선하게 되면 이론적으로 4배의 Data Rate 향상이 이루어진다. 물리적인 RF 변조방식을 ASK에서 QPSK로 바꿔 간단히 Data Rate을 개선하게 되면 회로구현의 경제성이 향상되어 DSRC 응용 서비스가 활성화 될 것이다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.52-60
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• 2001

In this paper proposes a multi-carrier MFSK-DPSK/DS-CDMA combined modulation techniques in Nakagami fading environment. Also, multi-carrier DS-CDMA combined system is a promising technique for mobile communications systems, since it has a strong immunity to multipath fading and increasing bandwidth efficiency. The modulations under consideration are noncoherent M-ary frequency shift keying (MFSK)and an MFSK based joint frequency phase modulation utilizing differential phase shift keying (DPSK). With the result, performance improvement of power efficiency and bandwidth efficiency combined system in multi-carrier MFSK-DPSK/DS-CDMA are better then conventional communication system.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.205-211
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• 2006

This paper considers the maximum likelihood (ML) detection of 16-ary differential amplitude and phase shift keying (DAPSK) in Rayleigh fading channels. Based on the conditional likelihood function, two new receiver structures, namely ML symbol-by-symbol receiver and ML sequence receiver, are proposed. For the symbol-by-symbol detection, the conventional DAPSK detector is shown to be sub-optimum due to the complete separation in the phase and amplitude detection, but it results in very close performance to the ML detector provided that its circular amplitude decision thresholds are optimized. For the sequence detection, a simple Viterbi algorithm with only two states are adopted to provide an SNR gain around 1 dB on the amplitude bit detection compared with the conventional detector.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2009-2010
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• 2006

This paper presents an adaptive line coupler to match input impedance of the Power line Communication(PLC) modem between access impedance of the power line. This line coupler provides maximum signal power transmiting capability, high reliability. The structure of this coupler is simple and designed to make a easy and low cost. The proposed line coupler is suitable for Amplitude Shift Keying(ASK) or Phase Shift Keying(PSK) modem. To figure out our models, the analysis of the transmitting features of power line channel is performed in the time domain at the carrier frequency. As a result of this study, we present the values of capacitors in the capacitor bank and adaptive line coupler circuit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1998.11a
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• pp.389-393
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• 1998

SSB, VHF 등의 장비에 의한 무선통신은 아직도 중요한 정보전달의 수단으로 사용되고 있으며, 무선국으로부터 원거리에 설치되는 장비에 대해서는 전용회선을 사용하여 원격제어로 송ㆍ수신을 행하고 있다. 그러나 무선국에서 다수의 사용자가 다수의 장비에 임으로 접속하고 운용을 해야하는 환경에서는 ICS(Intergrated Communication System:통합통신시스템)의 회선접속 제어기가 요구된다. 본 논문에서는 ICS의 개발을 위하여 ASK(Amplitude Shift Keying) 변조방식에 의한 PTT(Press To Talk) 제어와 신호의 전송회로를 구성하여 실험하였고, 멀티-프로쎄싱에 의한 회선접속 제어기를 설계하여 통합 통신운용에 대한 알고리즘을 연구하였다. Keying에 의하여 m 신호를 단속하였고 지속되는 PTT 신호에 음성신호를 합성시켜 전송시키는 형태의 ASK 변조방식을 취하여 전송되도록 하였고, 회선접속 제어기는 master와 다수의 slave 프로쎄서를 멀티-프로쎄싱의 직렬데이터 전송방식으로 프로쎄서 상호간에 데이타가 전달되도록 구성하였다. 이에 따른 S/W 는 멀티-프로쎄싱의 인터럽트기법을 최대한 활용하여 원하는 회선에 정확히 접속되어 통신이 이루어지도록 설계하였다. 따라서 이 연구는 주파수 자원의 고갈과 통신량의 증가에 대한 대책의 일환으로 저비용의 시설로 재래식 장비의 운용 효율을 증대시키는 기술의 개발에 목적이 있다.

• Journal of information and communication convergence engineering
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• v.7 no.2
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• pp.152-156
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• 2009

This paper examines the BER performance of the recently proposed half-symbol-rate-carrier (HSRC) offset quadrature phase-shift-keying (OQPSK) receiver for high-speed data communication. A modified demodulation technique using a bit-time period signal integration, the bit-error-rate (BER) performance of the HSRC-OQPSK signal improves more than 4dB compared to that of a demodulation technique using a symbol-time period integration. This paper also examines the BER performance of modified demodulation with various band-limited channels modeled using low-pass filters, and the three different data-rate systems are simulated and compared with the performance of the system using the conventional demodulation technique.

• ETRI Journal
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• v.28 no.6
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• pp.793-795
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• 2006

When quadrature error exists, the shape of the M-ary phase shift keying (MPSK) signal constellation becomes skewed-elliptic. Each MPSK symbol takes on a different symbol error probability (SEP) value. The analytical results presented thus far have been derived from studies which examined the SEP problem assuming that the SEP of each MPSK symbol is equally likely; therefore, those results should not be treated as offering a complete solution. In this letter, we present a new and more complete solution to the SEP problem of MPSK by relaxing the above assumption and finding the expressions for the average as well as individual SEP in the presence of quadrature error.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06c
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• pp.277-279
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• 2006

본 논문에서는 Wireless Sensor Networks(WSNs)에서 에너지 소모를 줄이기 위해 사용되는 In-network processing에 대하여 보안이 강화된 레벨 키 기반의 Infrastructure를 설계하여 노드의 전복 공격에 대해 안전한 패킷 포워딩을 보장하는 프로토콜을 제시한다. 이러한 계층적 구조를 가지는 보안 Framework는 노드의 추가 혹은 퇴거가 발생했을 때 Re-keying 비용을 획기적으로 줄일 수 있다. 시뮬레이션 결과, 전체 네트워크 중 전복된 노드가 40%를 차지할 때, 제안된 프로토콜을 사용하게 되면 약 3%의 추가적인 라우팅 오버헤드 비용으로 15%의 향상된 종단간 패킷 전송률을 보여준다. 또한 Re-keying을 할 때 OFT와 비교하여 통신비용을 현저하게 줄일 뿐만 아니라 서버의 도움 없이 키를 업데이트 하기 때문에 분산환경에 적합한 특징을 갖는다.