• Title/Summary/Keyword: soft-input soft-output

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Low Complexity Iterative Detection and Decoding using an Adaptive Early Termination Scheme in MIMO system (다중 안테나 시스템에서 적응적 조기 종료를 이용한 낮은 복잡도 반복 검출 및 복호기)

  • Joung, Hyun-Sung;Choi, Kyung-Jun;Kim, Kyung-Jun;Kim, Kwang-Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.8C
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    • pp.522-528
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    • 2011
  • The iterative detection and decoding (IDD) has been shown to dramatically improve the bit error rate (BER) performance of the multiple-input multiple-output (MIMO) communication systems. However, these techniques require a high computational complexity since it is required to compute the soft decisions for each bit. In this paper, we show IDD comprised of sphere decoder with low-density parity check (LDPC) codes and present the tree search strategy, called a layer symbol search (LSS), to obtain soft decisions with a low computational complexity. In addition, an adaptive early termination is proposed to reduce the computational complexity during an iteration between an inner sphere decoder and an outer LDPC decoder. It is shown that the proposed approach can achieve the performance similar to an existing algorithm with 70% lower computational complexity compared to the conventional algorithms.

Gesture Interaction Design based on User Preference for the Elastic Handheld Device

  • Yoo, Hoon Sik;Ju, Da Young
    • Journal of the Ergonomics Society of Korea
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    • v.35 no.6
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    • pp.519-533
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    • 2016
  • Objective: This study lays its aims at the definition of relevant operation method and function by researching on the value to be brought when applying smart device that can hand carry soft and flexible materials like jelly. Background: New technology and material play a role in bringing type transformation of interface and change of operation system. Recently, importance has been increased on the study of Organic User Interface (OUI) that conducts research on the value of new method of input and output adopting soft and flexible materials for various instruments. Method: For fulfillment of the study, 27 kinds of gestures have been defined that are usable in handheld device based on existing studies. Quantitative research of survey was conducted of adult male and female of 20s through 30s and an analysis was done on the function that can be linked to gestures with highest level of satisfaction. In order to analyze needs and hurdles of users for the defined gesture, a focus group interview was conducted aiming at the groups of early adopters and ordinary users. Results: As a result, it was found that users have much value regarding usability and fun for elastic device and analysis could be conducted on preferred gesture and its linkable functions. Conclusion: What is most significant with this study is that it sheds new light on the values of a device made of elastic material. Beyond finding and defining the gestures and functions that can be applied to a handheld elastic device, the present study identified the value elements of an elastic device - 'usability and 'fun' -, which users can basically desire from using it. Application: The data that this study brought forth through preference and satisfaction test with the gestures and associated functions will help commercialize an elastic device in future.

DCM DC-DC Converter for Mobile Devices (모바일 기기용 DCM DC-DC Converter)

  • Jung, Jiteck;Yun, Beomsu;Choi, Joongho
    • Journal of IKEEE
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    • v.24 no.1
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    • pp.319-325
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    • 2020
  • In this paper, a discontinuous-conduction mode (DCM) DC-DC buck converter is presented for mobile device applications. The buck converter consists of compensator for stable operations, pulse-width modulation (PWM) logic, and power switches. In order to achieve small hardware form-factor, the number of off-chip components should be kept to be minimum, which can be realized with simple and efficient frequency compensation and digital soft start-up circuits. Burst-mode operation is included for preventing the efficiency from degrading under very light load condition. The DCM DC-DC buck converter is fabricated with 0.18-um BCDMOS process. Programmable output with external resistors is typically set to be 1.8V for the input voltage between 2.8 and 5.0V. With a switching frequency of 1MHz, measured maximum efficiency is 92.6% for a load current of 100mA.

Highly Reliable Triboelectric Rotational Energy Scavenger

  • Lee, Younghoon;Lee, Bada;Choi, Dukhyun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.397-397
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    • 2016
  • Triboelectric nanogenerators (TENG) can produce power from ambient mechanical sources and have strong points of high output performance, light weight, low cost, and easy manufacturing process. It is expected that TENG can be utilized in the fields of wireless electronics and self-powered devices in the world which pays attention to healthcare and the IoT. In this work, we focus on scavenging ambient rotational energy by using a durably designed TENG. In previous studies regarding harvesting rotation mode energy, the devices were based on sliding mechanism and durability was not considered as a major issue. However friction by rotation causes reliability problems due to wear and tear. Therefore, in this study, we convert rotary motion to linear motion utilizing a cam by which we can then utilize contact-mode TENG and improve device reliability. In order to increase output performance, bumper springs were used below the TENG and the optimum value for the bumper spring constant was analyzed theoretically. Furthermore, the inserting a soft substrate was proposed and its effect on high output was determined to be due to an increase in the contact area. By increasing the number of cam noses, the output frequency was shown to increase linearly. For the purpose of maximum power transfer, the input impedance of the device was determined. Finally, to demonstrate the use of the C-TENG as a direct power source, it was installed on a commercial bicycle wheel and connected to 180 LEDs. In conclusion we present a rotational motion TENG energy scavenger system designed for enhanced durability and optimized output by appropriate choice of spring constants and substrate.

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Sparsity Adaptive Expectation Maximization Algorithm for Estimating Channels in MIMO Cooperation systems

  • Zhang, Aihua;Yang, Shouyi;Li, Jianjun;Li, Chunlei;Liu, Zhoufeng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.8
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    • pp.3498-3511
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    • 2016
  • We investigate the channel state information (CSI) in multi-input multi-output (MIMO) cooperative networks that employ the amplify-and-forward transmission scheme. Least squares and expectation conditional maximization have been proposed in the system. However, neither of these two approaches takes advantage of channel sparsity, and they cause estimation performance loss. Unlike linear channel estimation methods, several compressed channel estimation methods are proposed in this study to exploit the sparsity of the MIMO cooperative channels based on the theory of compressed sensing. First, the channel estimation problem is formulated as a compressed sensing problem by using sparse decomposition theory. Second, the lower bound is derived for the estimation, and the MIMO relay channel is reconstructed via compressive sampling matching pursuit algorithms. Finally, based on this model, we propose a novel algorithm so called sparsity adaptive expectation maximization (SAEM) by using Kalman filter and expectation maximization algorithm so that it can exploit channel sparsity alternatively and also track the true support set of time-varying channel. Kalman filter is used to provide soft information of transmitted signals to the EM-based algorithm. Various numerical simulation results indicate that the proposed sparse channel estimation technique outperforms the previous estimation schemes.

Soft-Decision Algorithm with Low Complexity for MIMO Systems Using High-Order Modulations (고차 변조 방식을 사용하는 MIMO 시스템을 위한 낮은 복잡도를 갖는 연판정 알고리즘)

  • Lee, Jaeyoon;Kim, Kyoungtaek
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.6
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    • pp.981-989
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    • 2015
  • In a log likelihood ratio(LLR) calculation of the detected symbol, multiple-input multiple-output(MIMO) system applying an optimal or suboptimal algorithm such as a maximum likelihood(ML) detection, sphere decoding(SD), and QR decomposition with M-algorithm Maximum Likelihood Detection(QRM-MLD) suffers from exponential complexity growth with number of spatial streams and modulation order. In this paper, we propose a LLR calculation method with very low complexity in the QRM-MLD based symbol detector for a high order modulation based $N_T{\times}N_R$ MIMO system. It is able to approach bit error rate(BER) performance of full maximum likelihood detector to within 1 dB. We also analyze the BER performance through computer simulation to verify the validity of the proposed method.

Design of PFM Boost Converter with Dual Pulse Width Control (이중 펄스 폭을 적용한 PFM 부스트 변환기 설계)

  • Choi, Ji-San;Jo, Yong-Min;Lee, Tae-Heon;Yoon, Kwang-Sub
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.9
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    • pp.1693-1698
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    • 2015
  • This paper proposed a PFM(pulse-frequency modulator) boost converter which has dual pulse-width. The PFM boost converter is composed of BGR(band gap voltage reference generating circuit), voltage reference generating circuit, soft-start circuit, error amplifier, high-speed comparator, inductor current sensing circuit and pulse-width generator. Converter has different inductor peak current so it has wider load current range and smaller output voltage ripple. Proposed PFM boost converter generates 18V output voltage with input voltage of 3.7V and it has load current range of 0.1~300mA. Simulation results show 0.43% output voltage ripple at ligh load mode and 0.79% output voltage ripple at heavy load mode. Converter has efficiency 85% at light lode mode and it has maximum 86.4% at 20mA load current.

Model Based Investigation of Surface Area Effect on the Voltage Generation Characteristics of Ionic Polymer Metal Composite Film (모델 기반의 이온 전도성 고분자 필름 금속 복합체의 표면적 증가에 따른 전압생성 특성 변화에 관한 연구)

  • Park, Kiwon;Kim, Dong Hyun
    • Composites Research
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    • v.29 no.6
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    • pp.401-407
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    • 2016
  • IPMC is composed of thin ion conductive polymer film sandwiched between metallic electrodes plated on both surfaces. Ionic Polymer-Metal Composite (IPMC) generates voltages when bent by mechanical stimuli. IPMC has a potential for the variety of energy harvesting applications due to its soft and hydrophilic characteristics. However, the large-scale implementation is necessary to increase the output power. In this paper, the scale-up of surface area effect on voltage generation characteristics of IPMC was investigated using IPMC samples with different surface areas. Also, a circuit model simulating both the output voltage and its offset variations was designed for estimating the voltages from IPMC samples. The proposed model simulated the output voltages with offsets well corresponding to various frequencies of input bending motion. However, some samples showed that the increase of error between real and simulated voltages with time due to the nonlinear characteristic of offset variations.

Analysis of Communication Performance According to Detection Sequence of MMSE Soft Decision Interference Cancellation Scheme for MIMO System (다중 입출력 시스템 MMSE 연판정 간섭 제거 기법의 검출 순서에 따른 통신 성능 분석)

  • Lee, Hee-Kwon;Kim, Deok-Chan;Kim, Tae-Hyeong;Kim, Yong-Kab
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.12 no.6
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    • pp.636-642
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    • 2019
  • In this paper, we analyzed BER (Bit Error Rate) communication performance according to the detection order of MMSE (Minimum Mean Square Error) based soft decision interference cancellation. As the detection order method, antenna index order method, absolute value magnitude order method of channel elements, absolute value sum order method of channel elements, and SNR (Signal Noise Ratio) order method are proposed. BER performance for the scheme was measured and analyzed. As a simulation environment, 16-QAM (Quadrature Amplitude Modulation) modulation is used in an uncoded environment of an M×M multiple-input multiple-output system, and an independent Rayleigh attenuation channel is considered. The simulation results show that the performance gain is about 1.5dB when the SNR-based detection order method is M=4, and the performance gain is about 3.5dB when M=8 and about 3.5dB when M=16. The more BER performance was confirmed, the more the detection order method of the received signal prevented the interference and error spreading occurring in the detection process.

Joint Kalman Channel Estimation and Turbo Equalization for MIMO OFDM Systems over Fast Fading Channels

  • Chang, Yu-Kuan;Ueng, Fang-Biau;Shen, Ye-Shun;Liao, Chih-Yuan
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.11
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    • pp.5394-5409
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    • 2019
  • The paper investigates a novel detector receiver with Kalman channel information estimator and iterative channel response equalization for MIMO (multi-input multi-output) OFDM (orthogonal frequency division multiplexing) communication systems in fast multipath fading environments. The performances of the existing linear equalizers (LE) are not good enough over most fast fading multipath channels. The existing adaptive equalizer with decision feedback structure (ADFE) can improve the performance of LE. But error-propagation effect seriously degrades the system performance of the ADFE, especially when operated in fast multipath fading environments. By considering the Kalman channel impulse response estimation for the fast fading multipath channels based on CE-BEM (complex exponential basis expansion) model, the paper proposes the iterative receiver with soft decision feedback equalization (SDFE) structure in the fast multipath fading environments. The proposed SDFE detector receiver combats the error-propagation effect for fast multipath fading channels and outperform the existing LE and ADFE. We demonstrate several simulations to confirm the ability of the proposed iterative receiver over the existing receivers.