• Journal of Convergence for Information Technology
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• v.10 no.5
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• pp.1-7
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• 2020

This paper proposes a link adaptation method for Underwater Internet of Things (IoT), which reduces power consumption of sensor nodes and improves the throughput of network in underwater IoT network. Adaptive Modulation and Coding (AMC) technique is one of link adaptation methods. AMC uses the strong correlation between Signal Noise Rate (SNR) and Bit Error Rate (BER), but it is difficult to apply in underwater IoT as it is. Therefore, we propose the machine learning based AMC technique for underwater environments. The proposed Modulation Coding and Scheme (MCS) prediction model predicts transmission method to achieve target BER value in underwater channel environment. It is realistically difficult to apply the predicted transmission method in real underwater communication in reality. Thus, this paper uses the high accuracy BER prediction model to measure the performance of MCS prediction model. Consequently, the proposed AMC technique confirmed the applicability of machine learning by increase the probability of communication success.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.669-676
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• 2008

The adaptive resource optimization problem in multi-input multi-output orthogonal frequency division multiple access (MIMO-OFDMA) systems is addressed. This paper, adaptive modulation and coding(AMC) and power control algorithms is proposed with SFC(Space-Frequency Coding), which aims to maximize the system capacity based on the CQI(Channel Quality Information). Firstly, power level is decided to each sub-channels with received feedback signal to noise ratio(SNR). In the second step, sub-carriers are allocated according to modulation type. Simulation results show that the proposed algorithm achieves a better performance than conventional algorithm in terms of capacity.

• 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.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.11-14
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• 2004

Digital Video Broadcasting - Satellite (DVB-S) [1] (EN 300 421(bibliography)) was introduced as a standard in 1994. However, by combing with higher order modulation, promise more powerful alternatives to the DVB-S / DVB-DSNG coding and modulation schemes. Variable rate coding and modulation (VCM) may employed to provide different levels of error protection to different service components. Adaptive coding and modulation (ACM) provides more exact channel protection and dynamic link adaptation to propagation conditions, targeting each individual receiving terminal. By these reasons, DVB-S2 introduced. This paper derives exact symbol error rate(SER) of 16-Amplitude Phase Shift Keying(APSK) modulation by using Craig's formula. 16-APSK modulation is used in DVB-S2. The difference between Union Bound and Craig's formula is 1.26dB in low SNR and 0.1dB in high SNR.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.6
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• pp.1-7
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• 1978

This paper deals with speech digitization and bandwidth compression techniques, particularly two predictive coding methods-namely, adaptive differential pulse code modulation(ADPCM) and adaptive delta modulation(ADM). The principle of a typical adaptive quantizer that is used in ADPCM is explained, and discussed. Also, three companding methods(instantaueous, 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 inerits of each coder are discussed.

• Journal of Communications and Networks
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• v.1 no.2
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• pp.99-110
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• 1999

The adaptive coded modulation (ACM) is a promissing way to provide a substantial improvement in spectral efficiency for slow fading channels. The basic idea is to adapt system functional-ity such as modulation, coding, information rate, and transmission power to varying channel conditions. In this work, the potential of adaptive coded modulation is investigated using cut-off rate anal-ysis in a unified way and using computer simulation. The anal-ysis includes various effects of fading channels such as feedback delay and channel prediction error. It was shown that the adaptive coded modulation can provide several folds of increase in spectral efficiency compared to a fixed coded-modulation system employing QPSK when channel varies slowly.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.10-19
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• 2012

In this paper, we propose an Adaptive Modulation and Coding (AMC) scheme using relay protocols generally known as Relay Node (RN). The AMC scheme is used for improving the throughput and a reliability of a communication system, because of the nature of different modulation and coding schemes. We analyze the performance of relay protocols with the AMC scheme and observed that relay protocols with the AMC scheme is capable of providing better average throughput at a lower Signal to Noise Ratio (SNR) level as compared to the conventional scheme with no AMC. We perform Monte Carlo simulations with Long Term Evolution-Advanced (LTE-A) parameters to prove the performance comparison of adaptive Modulation and Coding Scheme (MCS) relay protocols with the non-adaptive MCS relay protocols. The simulation results of the proposed system with adaptive MCS prove that among the Amplify-and-Forward (AF), Decode-and-Forward (DF) and DeModulate-and-Forward (DMF), the DMF protocol performs best at a lower SNR value and also provides better average throughput.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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• pp.2493-2508
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• 2012

The performance of a MIMO system with adaptive modulation (AM) and space-time coding over Ricean fading channels for perfect and imperfect channel state information (CSI) is presented. The fading gain value is partitioned into a number of regions by which the modulation is adapted according to the region the fading gain falls in. Under a target bit error rate (BER) constraint, the switching thresholds for AM are given. Based on these results, we derive the calculation formulae of the theoretical spectrum efficiency (SE) and average BER. As a result, closed-form SE expression and accurate BER expression are respectively obtained. Besides, using the approximation of complementary error function, a tightly closed-form approximation of average BER is also derived to simplify the calculation of accurate theoretical BER. Computer simulation shows that the theoretical SE and BER are in good agreement with the corresponding simulation, and the approximate BER is also close to the accurate one. The results show that the AM scheme in Ricean fading channel provides better SE than that in Rayleigh fading channel due to the direct-path propagation, and has performance degradation in SE and BER for imperfect CSI.

• 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.

• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1623-1630
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• 2005

Adaptive modulation and coding (AMC), which has a number of variation levels in accordance with the fading channel variation, is a promising technique for communication systems. In this paper, we present an AMC method using the cluster in OFDM system for bandwidth efficiency and performance improvement. The AMC schemes applied into each cluster or some clusters are determined by the minimum or the average SNR value among all the sub carriers within the corresponding cluster. It is important to find the optimal information on cluster because AMC performance can be varied according to the number and position of cluster. It is shown by computer simulation that the AMC method outperforms the fixed modulation in terms of bandwidth efficiency and its performance can be determined by the position and number of clusters.