• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.1
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• pp.37-45
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• 1982

We have analyzed the effect of multipath cochannel interference and Gaussian noise on binary DPSK systems used in land mobile radio communications. Considering multipath channel as non-selective Rayleigh channel, we have found a gnenral equation for bit error rates (BER) deriving the probability density function (p.d.f) of output of phase detector. The numerical results are shown in graphs and discussed as functions of carrier to noise power ratio (CNR), carrier to interferer power ratio (CIR) and correlation of signal component over the pulse length.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.899-906
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• 1997

It is known that the Differential Phase Shift Keying (DPSK) modulation scheme in the coherent optical communication system is suitable for design of long-distance transmission system because its receiver performance is 3-5dB better than ASK and FSK. In this paper, we descrive a fundamental understanding of the effects of laser phase noise on the performance of coherent lighwave communication systems. Formulas are derived for the bit error rate in homodyne and heterodyne DPSK. Based on detailed mathematical analysis and estimates, we explain the following finding. DPSK can operates at rates only 300 times greater than the laser linewidth.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.94-98
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• 2013

A report of security problems and simultaneous operation limits of Standard tone currently used for FTS introduces the development of a next generation FTS. In this paper, BER performance by modulations and channel coding methods for EFTS are compared. Simulation results show that coherent modulations have better BER performance than noncoherent modulations. However the environments of a lunching vehicle may cause serious problems in achieving and maintaining synchronization and the increasing complexity of coherent systems also increases reliability problems. Therefore noncoherent systems are suitable for FTS even though BER performace of noncoherent systems is lower than coherent systems. Noncoherent DPSK has better BER performance than noncoherent CPFSK. However the PEP of noncoherent DPSK is 0.8dB higher than noncoherent CPFSK. Therefore a transmitter of noncoherent DPSK has more output power than noncoherent CPFSK. Convoltional code has better BER performance than RS code. However RS code has a tendency of steeply decreasing BER near the wanted $E_b/N_0$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.34-42
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• 2000

In this paper, the closed form expression for the average bit error probability(BER) is derived for diversity reception using an L-branch maximal ratio combining(MRC) system which has same fading index and different fading index. Also, the BER to have same average power and Nakagami m-distribution for a generalized selection combining(SC) is derived, whereby the signal with the largest amplitude is selected from the original diversity branches in the channel, the order statistics is applied. Especially, when L is 1 in a selective diversity, the derived expression leads to that of DPSK in which SC is not applied in Nakagami fading. Changing the diversity branch L and fading index m, we compare the performance of MRC and SC.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.461-464
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• 2000

본 논문에서는 위성통신 환경에서 DS/CDMA DPSK 시스템의 성능을 분석한다. 성능분석의 척도로 비트오류확률을 사용한다. 위성전송로는 쉐도잉이 있는 라이시안 페이딩 전송로로 모델링한다. 수치계산의 결과, 위상잡음이 존재할 때 비트오율 성능이 저하되므로 시스템 용랑이 감소될 것이 예상된다. 또한 위성전송로에서는 쉐도잉이 시스템 전체 성능에 커다란 영향을 미침을 알 수 있다. 본 논문에서의 분석은 DS/CDMA 기반의 위성통신 시스템 설계에 적용할 수 있다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.7
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• pp.1-11
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• 1993

The bit error rates of DS/SSMA DPSK system with diversity and FEC channel coding in Rayleigh fading and log-normal shadowing channel are evaluated. Microscopic postdetection diversity and macroscopic selection diversiity are used to mitigate the effects of Rayleigh fading and log-normal shadowing, respectively. The numerical results show that the composite use of diversity and channel coding is very efficient for improving system performance compared to their respective uses.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.223-224
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• 2013

본 논문은 차등 위상 편이 변조(DPSK) 시스템에서 파일럿 없이 주파수 추정하는 기법을 제안한다. 제안하는 주파수 동기오차 추정 방식은 파일럿을 사용하지 않고 DPSK 변조 방식에서 연속되는 신호의 차등 위상신호를 전송하는 특성을 사용하는 블라인드 기법이다. DPSK 신호의 위상 차분은 주파수 오차 추정을 실행 할 때 페이즈를 증가시켜 왜곡으로 작용하게 되는데, 본 논문에서는 간단한 상관기와 제곱기로 이러한 특성을 제거하여 주파수 추정 성능을 증가 시킨다. 알고리즘의 검증은 수식과 컴퓨터 시뮬레이션으로 수행한다.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.107-112
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• 1986

This paper presents one method to resolve the end-to-end digital connectivity through 2-wire subscriber loop. This system which consists of the subscriber`s device and the line termination device makes use of the advantages of time compressed multiplexing and modified DPSK. Experimental results show that the transmission range of the lab test covers 2km and that of the field test covers 1.5km.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.3
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• pp.112-119
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• 1982

An experimental 2400bps modem emlpoying 4-phase DPSK in compliance with the CCITT recommendation V.26 is developed. Integrated circuits are used throughtout the circuit implementation, including active filters and a semiconductor delay line. A new timing recovery scheme is proposed and adopted successfully. The error rate perfromance is found to be in fair agreement with the theoretical prediction.