• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.139-140
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• 2010

This paper presents an indoor prototype for wireless digital signal transmission using Visible Light Communications (VLC) in which high power Light Emitting Diode (LED) is used. Using low cost and off-the-shelf components, the transmitter module is constructed using an AVR Atmega128 microcontroller and commercial white beam LEDs. Modulating the light intensity of the LED enables digital signals to be transmitted across the optical link. The receiver module employs a high speed PIN photodetector for optical signal detection and a recovery circuit for optical-electro signal conversion. By sending digitalized data via VLC technology, many applications can be realized in the areas of consumer advertising, traffic safety information and disaster control.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.121-128
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• 2008

In the department of mobile communication technology and satellite communication technology, wireless communication technology division is very important by transmitting and receiving the signals in wireless link environment. Most of all, the components which comprises the transmitter and receiver can decide the RF(Radio Frequency) system performances. Therefore to assure the reliability in the satellite communication field, it is essential to acquire the competitiveness by developing the highly integrated and compact components by means of MMIC(Monolithic Microwave Integrated Circuit) technology. MMIC is the designing and fabricating technology for the RF components. This paper introduces the MMIC technology and describes the technological trend and prospect in the satellite application.

• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.273-276
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• 2011

우리는 감성 공학에 기반하여 일상 생활 속에서 비침습적이면서 사용하기 간편한 광전용적맥파신호를 계측하고 분석하는 이어폰형 생체 신호 측정 시스템에 관하여 연구하였다. 생체 신호 측정 시스템에서는 광전용적맥파(photoplethysmograph, PPG)와 3축 가속도로 생체 신호와 운동 신호를 활용하였다. 수신된 생체 신호인 광전용적맥파 신호는 Peak 검출 및 전처리 알고리즘을 통하여 심박동변동성(heart rate Variablity,HRV)에 대한 시계열 정보로 변환하고 고속 퓨리에 변환(Fast Fourier Transfirm, FFT)과 전력 스펙트럼 밀도 분석(Power Spectrum Density, PSD)방법으로 교감과 부교감 신경 활성도 변화를 관측하였고, 운동 센서로 움직임을 관측하였다. 수신부 시스템은 안드로이드 기반의 자바 어플리케이션으로 스마트 폰에서 구현하였고, 송신부인 이어폰 생체정보 측정모듈로 맥파를 측정하여 상황에 따라 변화하는 자율 신경계의 활성도비율을 확인하였다.

• Journal of Power Electronics
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• v.19 no.2
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• pp.602-611
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• 2019

The major drawbacks of magnetic resonant coupled wireless power transfer (WPT) to the embedded sensors on spindles are transmission instability and low efficiency of the transmission. This paper proposes a novel double-loop coil design for wirelessly charging embedded sensors. Theoretical and finite-element analyses show that the proposed coil has good transmission performance. In addition, the power transmission capability of the double-loop coil can be improved by reducing the radius difference and width difference of the transmitter and receiver. It has been demonstrated by analysis and practical experiments that a magnetic resonant coupled WPT system using the double-loop coil can provide a stable and efficient power transmission to embedded sensors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.4698-4716
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• 2017

Wireless signal transmission is influenced by environmental effects. These effects have also been challenging for Vehicular Ad hoc Network (VANET) in real-time communication. More specifically, in an urban environment, with high mobility among vehicles, a vehicle's status from the transmitter can instantly trigger from line of sight to non-line of sight, which may cause loss of real-time communication. In order to overcome this, a deterministic signal propagation model is required, which has less complexity and more feasibility of implementation. Hence, we propose a realistic path loss model which adopts ray tracing technique for VANET in a grid urban environment with less computational complexity. To evaluate the model, it is applied to a vehicular simulation scenario. The results obtained are compared with different path loss models in the same scenario based on path loss value and application layer performance analysis. The proposed path loss model provides higher loss value in dB compared to other models. Nevertheless, the performance of vehicle-vehicle communication, which is evaluated by the packet delivery ratio with different vehicle transmitter density verifies improvement in real-time vehicle-vehicle communication. In conclusion, we present a realistic path loss model that improves vehicle-vehicle wireless real-time communication in the grid urban environment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.83-89
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• 2016

In this paper, we apply the complementation principle of five prime substances to reduce the phase interference. The transmitter and receiver match the concepts of co-operative and conflict to the direct and indirect signals. The result shows we investigate the proposed network topology such as 5 prime substances (5 user networks). The key observation is that optimal symmetric degree of freedom (DoF) can be achieved for 5 user network with different channel coherence times by adaptively selecting the interference alignment scheme via controlling the alignment feasibility of the transmitted signals. Theoretical results demonstrate the effectiveness of the proposed 5 user networks are well matched to the wireless mobile channel environment to achieve the symmetric DoF for different channel coherence times which ensures that the proposed networks are applicable for dense wireless network applications. Modulo 3 functionality in 5 user network topology makes it easier for the transmitter cooperation to achieve the DoF of 2/3 with the help of the interference alignment schemes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.673-676
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• 2008

In wireless communications such as Bluetooth, Baseband should be able to minimize the DC bias of the data which passed the modem interface of either transmitter or receiver for the reliability of the circuit and the integrity of the data. The transmitter scrambles the data to send randomly to the error correction block and the receiver recovers the randomly spread data as they have been. To design the whitening block, it is important to select the prime polynomial for the filtering. In this paper, we designed a optimal whitening block using the prime polynomial $g(D)=D^7+D^4+1$ for hardware and area efficiency. The proposed hardware whitening block was described and verified using Verilog HDL and later to be automatically synthesized. The synthesized whitening block operated at 40Mhz normal clock speed of the target baseband microcontroller.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.4
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• pp.333-337
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• 2004

This paper describe a design of 5GHz OFDM baseband chip for IEEE 802.11a wireless LAN. The proposed device is consists of transmitter and receiver within a single FPGA chip. We applied single tap equalizer that use Normalized LMS algorithm to remove ISI that happen at high speed data transmission. And also, we used carrier wave frequency offset algorithm that use training symbol to remove ICI. The simulation results show the correct transmission without errors the between transmitter and receiver And we can remarkably reduce the number of register through the synthesized circuits by using DSP block and EMB(Embedded Memory Block). The target device for implementation of the synthesized circuits is Altera Stratix EPIS25FC672 FPGA and design platform is VHDL.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.106-112
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• 2013

In this paper, human exposure of wireless devices was analyzed for various positions of the transmitter. The scenario for the position of the transmitting antenna was decided after discussion with ADD(Agency for Defense Development), and Korean male phantom model developed by ETRI were used to conduct simulations. The SAR values were analyzed by changing the position of the transmitter, and compared with Korean EMF regulations and ICNIRP guidelines. Additionally, human exposure was also investigated for two typical postures which can be posed by war-fighter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.155-164
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• 2013

Two design techniques for more accurate and more convenient hybrid positioning system with visible light communication (VLC) and ad-hoc wireless network infrastructure are proposed, in order to overcome the problems of high estimation error, high cost, and limited service range of the conventional positioning techniques. First method is based on a non-carrier VLC based hybrid positioning technique for applications involving of low data rate optical sensing and narrow-range visible light reception from transmitter, and long-range positioning. The second method uses a 4 MHz carrier VLC-based hybrid positioning technique for a high data rate optical sensing and wide-range visible light receiving from transmitter, and mid-range positioning applications. In indoor environments with obstacles where there are long-range 7731.4cm and mid-range 2368cm distances between an observer and a target respectively, the hybrid positioning developed with two design techniques are tested, and the proposed system is verified and analyzed in this paper.