• Journal of Communications and Networks
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• v.17 no.3
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• pp.231-240
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• 2015

To facilitate the base station planning in high speed railway communication systems, it is necessary to consider the functional relationships between the base station transmit power and space parameters such as train velocity and cell radius. Since these functions are able to present some inherent system properties determined by its spatial topology, they will be referred to as the power-space functions in this paper. In light of the fact that the line-of-sight path persists the most power of the received signal of each passing train, this paper considers the average transmission rate and bounds on power-space functions based on the additive white Gaussian noise channel (AWGN) model. As shown by Monte Carlo simulations, using AWGN channel instead of Rician channel introduces very small approximation errors, but a tractable mathematical framework and insightful results. Particularly, lower bounds and upper bounds on the average transmission rate, as well as transmit power as functions of train velocity and cell radius are presented in this paper. It is also proved that to maintain a fixed amount of service or a fixed average transmission rate, the transmit power of a base station needs to be increased exponentially, if the train velocity or cell radius is increased, respectively.

• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.166-169
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• 2017

This paper describes atmospheric phenomena and effects for satellite-to-ground laser communication channel. Satellite laser communication has advantages such as very high bandwidth, inherent security, robustness to electromagnetic interference, unlicensed frequency band. However, satellite laser communication is affected by various factors. Transmission quality is degraded by factors as system loss, geometric loss, misalignment loss, atmospheric loss. Atmospheric loss is major factor of performance degradation. In this paper, the atmospheric phenomena such as absorption, scattering and turbulence are discussed and analyzed for developing satellite laser channel model and laser transmission scheme robust to atmospheric phenomena.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1925-1932
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• 2016

One of the major challenges in the design of wireless sensor network (WSN) is to reduce the energy consumption of sensor nodes for prolonging the network lifetime. In the sensor network, communication is the most energy consuming event. Therefore, most of the energy saving techniques conserve energy by adjusting different parameters of the trans-receiver. Among them, one of the promising methods is the transmission power control (TPC). In this paper, we investigated the effects of the link quality based TPC scheme employed to the IEEE 802.15.4 standard for energy saving. The simulation results demonstrated that the link quality based TPC scheme works effectively in conserving energy as compared to the conventional IEEE 802.15.4.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.12
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• pp.3200-3219
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• 2013

This paper proposes an adaptive combined scalable video coding (CSVC) system for video transmission over MIMO-OFDM (Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplexing) broadband wireless communication systems. The scalable combination method of CSVC adaptively combines the medium grain scalable (MGS), the coarse grain scalable (CGS) and the scalable spatial modes with the limited feedback partially from channel state information (CSI) of MIMO-OFDM systems. The objective is to improve the average of peak signal-to-noise ratio (PSNR) and bit error rate (BER) of the received video stream by exploiting partial CSI of video sources and channel condition. Experimental results show that the delivered quality using the proposed adaptive CSVC over MIMO-OFDM system performs better than those proposed previously in the literature.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.931-933
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• 1995

In this paper, we develop protype of wierless recognition system using low frequency. Application of this system is very broad. Namely, High-way toll gate, animal management, parking system and industral automation et al. This system is composed of controller, decoder and tag. Controller is personal PC, decoder is signal module and tag is mobile corresponder module. Modulation is ASK, 4,800bps, frequency is 120/60kHz and transmission length is about 80cm. And now we study improvement of stability, low power consumption, compact of tag and transmission length improvement.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.1
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• pp.39-45
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• 2009

OFDM is used for achieving a high-speed data transmission in mobile wireless communication systems. Conventionally, fast Fourier transform that is the main signal processing of OFDM is implemented using digital signal processing. The DSP FFT LSI requires large power consumption. Current-mode FFT LSI with analog signal processing is one of the best solutions for high speed and low power consumption. However, for the operation of current-mode FFT LSI that has the structure of parallel-input and parallel-output, current-mode serial-to-parallel and parallel-to-serial converter are indispensable. We propose a novel current-mode SPC and PSC and full chip simulation results agree with experimental data. The proposed current-mode SPC and PSC promise the wide application of the current-mode analog signal processing in the field of low power wireless communication LSI.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.4
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• pp.159-166
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• 2020

The IBC (Intra-Body Communication) benefits from a wireless communication system for exchanging various kinds of digital information through wearable electronic devices and sensors. The IBC using the human body as the transmission channel allows wireless communication without the transmitting radio frequency waves to the air. This paper discusses the results of experiments on electrostatic coupling IBC based on FSK (Frequency Shift Keying) and 1 bit error correction. We implemented FSK communication and 1 bit error correction algorithm using the MCU boards and aluminum tape electrodes. The transmitter modulates digital data using 50% duty square wave as carrier signal and transmits data through human body. The receiver performs ADC (Analog to Digital Conversion) on carrier signal from human body. In order to figure out the frequency of carrier signal from ADC results, we applied zero-crossing algorithm which is used to detect the edge characteristic in computer vision. Experiment results shows that digital data modulated as square wave can be successfully transmitted through human body by applying the proposed architecture of a 1ch GPIO as a transmitter and 1ch ADC for as a receiver. Also, this paper proposes 1 bit error correction technique for reliable IBC. This technique performs error correction by utilizing the feature that carrier signal has 50% duty ratio. When 1 bit error correction technique is applied, the byte error rate at receiver side is improved around 3.5% compared to that not applied.

• Journal of Sensor Science and Technology
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• v.20 no.2
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• pp.137-144
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• 2011

Wireless sensor network(WSN) has the potential to greatly effect many aspects of u-healthcare. By outfitting the potential with WSN, wearable sensor node can collects real-time data on physiological status and transmits through base station to server PC. However, there is a significant gap between WSN and healthcare. WSN has the limited resource about computing capability and data transmission according to bio-sensor sampling rates and channels to apply healthcare system. If a wearable node transmits ECG and accelerometer data of 4 channel sampled at 100 Hz, these data may occur high loss packets for transmitting human activity and ECG to server PC. Therefore current wearable sensor nodes have to solve above mentioned problems to be suited for u-healthcare system. Most WSN based activity and ECG monitoring system have been implemented some algorithms which are applied for signal vector magnitude(SVM) algorithm and ECG noise algorithm in server PC. In this paper, A wearable sensor node using integrated ECG and 3-axial accelerometer based on wireless sensor network is designed and developed. It can form multi-hop network with relay nodes to extend network range in WSN. Our wearable nodes can transmit 1-channel activity data processed activity classification data vector using SVM algorithm to 3-channel accelerometer data. ECG signals are contaminated with high frequency noise such as power line interference and muscle artifact. Our wearable sensor nodes can remove high frequency noise to clear original ECG signal for healthcare monitoring.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.215-222
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• 2019

A frequency hopping(FH) signal can change its carrier frequency during transmission and has spread-spectrum characteristics in these frequency bands. Therefore, FH signals are widely used in applications that require low-probability-of-intercept(LPI) and anti-jamming (AJ) abilities in wireless communication environments. In this study, the authors propose a method for generating hopping information (HI), which includes start time, dwell time, and hopping frequency for unknown FH signals. The proposed blind HI generation method produces signal detection information based on the spectrum data and then extracts HI using operational procedures for estimating the target FH signal's status, such as appearance, maintenance, and termination. Further, simulation results demonstrate that the proposed method provides accurate HI without detection omissions for various FH signals.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2141-2145
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• 2015

A new broadcasting signal transmission, which can save its channel bandwidth using compressive sensing(CS), is proposed in this paper. A new compression technique, which uses two dimensional discrete wavelet transform technique, is proposed to get high sparsity of multimedia image. A L1 minimization technique based on orthogonal matching pursuit is also introduced in order to reconstruct the compressed multimedia image. The CS enables us to save the channel bandwidth of wired and wireless broadcasting signal because various transmitted data are compressed using it. A $256{\times}256$ gray-scale image with compression rato of 20 %, which is sampled by 10 Gs/s, was transmitted to an optical receiver through 20-km optical transmission and then was reconstructed successfully using L1 minimization (bit error rate of $10^{-12}$ at the received optical power of -12.2 dB).