• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.64-65
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• 2001

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.128-129
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• 2002

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.4
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• pp.30-38
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• 1994

In this paper, we propose the parallel scrambling technique which is applicable in the multibit-interleaved multiplexing environment. For this, we introduce the concept of SSRG (simple shift register generator) and MSRG(modular shift register generator), and investigate their properties. We also introduce the concept of PSRG(parallel shift register generator) - parallel form of shift register generator, and consider realizations of PSRGs based on SSRGs and MSRGs. Finally, we show how to apply PSRGs to the parallel scrambling for the SDH system.

• Journal of the Optical Society of Korea
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• v.2 no.1
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• pp.38-41
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• 1998

The method of using fiber speckle patterns can be applied to the multiplexing of volume holograms. Fiber speckle patterns enable various multiplexing techniques such as shift, angular, and mode-scrambling methods Hybrid methods involving more than one multiplexing technique are also possible. Some images are stored and retrieved with one or two of multiplexing methods, and the experimental results are discussed.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.219-227
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• 2021

This paper proposed an Orthogonal Frequency Division Multiplexing (OFDM) based biomimetic communication method using a dolphin whistle which covertly transmits communication signals to allies. The proposed method divides the dolphin whistle into several time slots corresponding to a number of OFDM symbols, and modulates the communication signal by mapping differential phase shift keying (DPSK) symbols into subcarriers that have the frequency bands of the dolphin whistle in each slot. The advantages of the proposed method are as follows: In the conventional Chirp Spread Spectrum (CSS) and Frequency Shift Keying (FSK) based biomimetic communication methods, the discontinuity of the frequency contour is large, but the proposed method can reduce the discontinuity. Even if the modulation order is increased, the degradation of the mimicking performance is small. The computer simulations demonstrate that the Bit Error Rate (BER) and mimicking performance of the proposed method are better performance than those of the conventional CSS and FSK.

• ETRI Journal
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• v.44 no.3
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• pp.379-388
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• 2022

This study proposes a novel low-complexity algorithm for computing inverse fast Fourier transform (IFFT)/fast Fourier transform (FFT) operations in binary phase shift keying-modulated orthogonal frequency division multiplexing (OFDM) communication systems without requiring any twiddle factor multiplications. The peak-to-average power ratio (PAPR) reduction capacity of an efficient PAPR reduction technique, that is, H-SLM method, is evaluated using the proposed IFFT algorithm without any complex multiplications, and the impact of oversampling factor for the accurate calculation of PAPR is analyzed. The power spectral density of an OFDM signal generated using the proposed multiplierless IFFT algorithm is also examined. Moreover, the bit-error-rate performance of the H-SLM technique with the proposed IFFT/FFT algorithm is compared with the classical methods. Simulation results show that the proposed IFFT/FFT algorithm used in the H-SLM method requires no complex multiplications, thereby minimizing power consumption as well as the area of IFFT/FFT processors used in OFDM communication systems.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.126-127
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• 2002

• Journal of Positioning, Navigation, and Timing
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• v.11 no.3
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• pp.147-156
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• 2022

In this paper, we propose Time-Division-Multiplexing Tertiary Offset Carrier (TDMTOC), a novel GNSS modulation based on Tertiary Offset Carrier (TOC) modulation. The TDMTOC modulation multiplexes two three-level signals (i.e., -1, 0, and 1) while crossing over time, and is a type of TOC modulation designed specifically for signal multiplexing. The proposed modulation generates TDMTOC subcarriers of two different phases by simply combining two Binary Offset Carrier (BOC) subcarriers by addition or subtraction. TDMTOC has better correlation and spectral properties than conventional BPSK, BOC, and MBOC modulation techniques, and has good power and spectral efficiency since it can multiplex signals without power loss similar to time division multiplexing. To prove this, we introduce the multiplexing process of TDMTOC, and compare TDMTOC with Binary Phase Shift Keying (BPSK), BOC, Composite BOC (CBOC), and Time Multiplexed BOC (TMBOC) that are currently serviced in GNSS by simulations of various aspects. Through the simulation results, we prove that TDMTOC has better correlation property than modulations currently used in GNSS, less intersystem interference due to its wide spectrum property, and robustness in multipath and noise channel environments.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.233-236
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• 2001

Orthogonal freqency division multiplexing (OFDM) is an attractive technique for achieving high-bit-rate wireless data transmission. However, the potentially large peak-to-average power ratio (PAPR) has limited its application; An OFDM signal with the large PAPR can cause power degradation (In-band distortion) and spectral spreading (Out-of-band distortion) by being clipped passing through a power amplifier. Thus, we propose the combining algorithm of Hadamard transform and phase shift, which is ascribed to the relation between the correlation of the IFFT input sequence function and PAPR. Extensive computer simulations show that the combining algorithm is an effective technique to reduce PAPR.

• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.677-680
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• 2008

In this paper, a new orthogonal frequency division multiplexing (OFDM) with 3-dimensional (3-D) signal mapper is proposed. Here, the signal mapper consists of signals on the surface of Poincare sphere. If the signal points are uniformly distributed and normalized to have the same average power, the minimum Euclidean distance of a 3-D constellation is much larger than that of a 2-D constellation. Computer simulation shows that the proposed OFDM has much improved error performance as compared with the conventional system.