• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2177-2182
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• 2016

Using the existing exact but quite complicated symbol error rate (SER) expressions for M-ary phase shift keying (M-PSK) and M-ary differential phase shift keying (M-DPSK), we derive effective and concise closed-form asymptotic SER formulas especially in Rician-Nakagami fading channels. The derived formulas can be utilized to efficiently verify the achievable error rate performances of M-PSK and M-DPSK systems for the Rician-Nakagami fading environments. In addition, by exploiting the modulation gains directly obtained from the asymptotic SER formulas, we also theoretically demonstrate that M-DPSK suffers an asymptotic SER performance loss of 3.01dB with respect to M-PSK for a given M in Rician-Nakagami fading channels at high signal-to-noise ratio (SNR).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.5 no.1 s.9
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• pp.45-54
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• 2006

The UWB signal distortion in frequency selective channel has made it difficult to implement the channel estimator and the synchronizer of the UWB receiver. In this paper, we examine the performances of TR(Transmitted Reference) and DTR(Differential TR) UWB which use either reference pulse or differential method to estimate the channels. we also propose a FSK-based PRM(Pulse Repetition Modulation) UWB system as an another form of UWB system which is advantageous in frequency selective channel. Finally, resorting to statistical analysis, we examine the noise effect due to noisy reference at an auto-correlation(AcR) receiver. moreover, SNR dependance of the integration length in the AcR receiver is also investigated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.611-614
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• 2012

Space-Time Block Code (STBC) is a simple transmit diversity scheme mitigating detrimental effects of fading channel. However, STBC receivers require channel knowledge and suffer from inaccurate channel estimation. Differential Space-Time Modulation (DSTM) renders the receiver a choice of coherent detection or non-coherent detection, depending on the availability of the channel information. Based on the simulated BER performances of these two schemes over various normalized Doppler frequency scenarios using LTE-like parameters, a benefit of adaptively switching the receiver type is investigated.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.2
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• pp.37-44
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• 2002

In this paper, the Viterbi decoder containing new branch metrics of the squared Euclidean distance with multiple order phase differences is introduced in order to improve the bit error rate (BER) in the differential detection of the trellis-coded MDPSK-DFDM. The proposed Viterbi decoder is conceptually same as the sliding multiple phase differential detection method that uses the branch metric with multiple phase differences. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER peformance without sacrificing bandwidth and power efficiency. Also, the proposed algorithm can be used in the single carrier modulation.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.6
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• pp.1131-1136
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• 2020

Cooperative networks enhance the performance of communication systems by combining received signals from the several relay nodes where the source node transmits signals to relay nodes. In this paper, we analyze the effect of resource allocation in cooperative networks. We assume that the cooperative networks use the conventional modulation scheme between the source and relay nodes, and adopt space-time code between the relays and destination node. Both the synchronous and differential modulations are applied for the conventional scheme and differential modulation is used for the space-time code. We consider relay location and energy allocation for resource allocation, and the performance of cooperative networks depending on the number of relay is also investigated.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.3
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• pp.1-6
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• 1978

This paper deals with speech digitization and bandwidth compression techniques, particularly two predictive coding methods-namely, adaptive diferentia1 pulse code modulation(ADPCM) and adaptive delta modulation (ADM). The principle of a typical adoptive quantizer that is used in ADPCM is explained, and two analysis methods for the adaptive predictor coefficents, block and sequential analyses, are discussed. Also, three companding methods (instantaneous, syllabic, and hybrid companding) that are used in ADM are explained in detail, and their performances are compared. In addition, the performances of ADPCM and ADM as speech coders are compared, and the merits of each coder are discussed.

• The Magazine of the IEIE
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• v.12 no.5
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• pp.23-35
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• 1985

본 논문은 디지털 음성통신에서 사용되는 예측부호화(predictive coding) 방식에 관하여 기술하고 있다. 특히 전송속도가 16∼48kbit/s 대역에서 많이 사용하고 있는 adaptive differential pulse code modulation(ADPCM)과 adaptive delta modulation(ADM)에 관하여 중점적으로 토의한다. 또한 variable-rate ADPCM과 ADM에 관해서 기술하고, 이들 시스템의 noisy channel에서의 효과 및 성능개선방법, 그리고 PCM과의 transcoding에서의 문제점 등을 통의한다. ADPCM은 최근 CCITT에서의 표준화 결과로 앞으로 PCM과 함께 많이 쓰여질 전망이며, ADM은 시스템이 간단하고 또한 channel error에 강한 이유로 특수통신에 많이 쓰여질 것이다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.668-676
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• 2018

In satellite communications, a modulation technique with a low peak-to-average power ratio, high transmission efficiency, and low bit error rate(BER) is required, and differential amplitude and phase shift keying(DAPSK) modulation technique has been appraised as a technology that meets these requirements. However, because conventional DAPSK modulation uses a regular constellation diagram, the Euclidean distance between the symbols in the inner concentric circles of the constellation are quite short. Such a characteristic degrades the BER. In this paper, we propose a DAPSK system that uses an efficient constellation assignment to improve the performance of existing DAPSK systems and evaluate the performance of the proposed scheme. From the simulation results, we confirm that the proposed 16-DAPSK system achieves an signal-to-noise ratio gain of 0.8 dB over the conventional approach at a BER condition of $10^{-4}$ when the number of symbols used in the symbol detector of the receiver is 2.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.1-7
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• 2012

The conventional Zhu's differential space-time modulation(DSTM) based on quasi-orthogonal design adopted a complex precoder in order to allow an independent joint detection of two complex symbols without any channel informations at a receiver. In this paper, by simply replacing the complex precoder used in Zhu's DSTM with a real precoder, a new DSTM is presented for four transmit antennas. The real precoder enables the receiver to decode two real symbols pair separately, and thus the new DSTM has greatly reduced decoding complexity compared to the Zhu's DSTM. By computer simulation results, the proposed scheme is shown to exhibit almost identical or improved error performance compared to the existing DSTMs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.151-155
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• 2016

In this paper, we present the LED dimming control system by using ADPCM (Adaptive Differential Pulse Code Modulation). This ADPCM apparatus accurately controls the LED current with high resolution reducing the RFI (radio frequency interference) due to the spreading out of the harmonics of current of pulses. Additionally, this makes it easier to increase the accuracy of control operation. This study introduces to make a digitally controlled circuit for controlling LED with high-energy efficient by adopting pulse current to LED. The LED current drive system we designed are two systems, the digitally-controlled unit and analog switching mode power supply unit, can be developed separately. The simulation shows the sigma delta modulation of digital to analog converter's output when the input level is 0.7. From this simulation, the output is approached to accurately 0.15% to target value with 510 pulses.