• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1095-1102
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• 1991

In this paper, we proposed the differential demodulation technique of 2-h CPM and analyzed its error performances. We derived the sets of modulation indices of 2-h phase codes adequate to the differential detection. The power spectra of 2-h CPM signals with various sets of mudulation indices are illustrated and compared, Besides, the error performances for the differential detectors are calculated and detectors using Viterbi algorithm are compared and analyzed by computer simulations.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.313-318
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• 2005

We propose an active stabilization method for the receiver of NRZ-DPSK transmission. The 1-bit delayed Mach-Zehlder interferometer is thermally controlled to maintain the largest DC component power ratio between the constructive and destructive output ports, for the optimum transmission condition. This method is very cost effective since no additional components are required. Experimental results show that the proposed scheme guarantees error free performance even when there was ~ 1 GHz optical carrier frequency fluctuation in 10 Gbps transmission.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.3
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• pp.54-62
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• 1993

In this paper, performance comparisions of MTCM systems with 8DPSK over mobile communication channels are obtained by computer simulation. The multiple symbol differential detection scheme is introduced in order to improve the bit error rate performance in the detection of the trellis-coded 8DPSK system. Rician fading channels are used as test channels. The simula- tion results show that the trellis-coded 8DPSK system with multiple symbol detection gives better performance than that of the uncoded DQPSK system. And symbol by symbol interleaving method gives better performance than the symbol pair interleaving method.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.06a
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• pp.110-115
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• 1990

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.3
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• pp.223-229
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• 2004

Recently, OFDM and STC techniques have been considered to be candidate to support multimedia services in the next generation mobile radio communications and have been developed the many communications systems in order to achieve the high data rates. In this paper, we propose the Trellis-Coded Differential Space Time Modulation-OFDM system with multiple symbol detection. The Trellis-code performs the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbl decoder improves BER performance without sacrificing bandwidth and power efficiency.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.351-354
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• 2008

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.52-57
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• 1990

• Journal of IKEEE
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• v.22 no.3
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• pp.800-804
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• 2018

This paper presents a novel HF band differential quadrature phase-shift keying (DQPSK) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 3.6 kbps with a bandwidth of about 3 kHz. In a digital modem, OFDM with 32-point fast Fourier transform is used. In the system, each subcarrier uses DQPSK modulation. Hence, a demodulator does not require carrier phase recovery and symbol timing recovery. And, each subcarrier employs CRC error check code individually. By using CRC code for each subcarrier, bit error caused by multipath fading can be recovered simply.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.1 s.4
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• pp.117-125
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• 2004

Space-time coding and modulation exploit the presence of multiple transmit antennas to improve performance on multipath Rayleigh fading channels. In this paper, we propose the Trellis-Coded Differential Space Time Modulation-OFDM system with multiple symbol detection. The Trellis-code perform the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the Unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.807-815
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• 2003

MultiCode-CDMA (MC-CDMA) system of chip level MPSK incorporating with clipper (MP-CDMA)[l] shows constant envelope signal which can mitigate the performance degradation due to nonlinear transmit amplifier. In this paper, modulation is modified to carry out differential encoded MPSK rather than MPSK. The modified system is called DMP-CDMA. DMP-CDMA using differential detection has advantages on receiver complexity and pilot overhead. However, it is inferior to coherent detection by about 4.0dB due to inherent power inefficiency of noncoherent detection and the error propagation. Multiple symbol differential detection is employed in order to improve DMP-CDMA using differential detection. As the result, the performance of DMP-CDMA system is improved about 3.6dB compared to differential detection.