• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1383-1388
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• 2011

Due to many recent activities on enforcement of the intensified environmental regulation such as the policies of curbing the greenhouse gas and the Restriction of Hazardous Substances (RoHS), the usage of Light emitting diode (LED) has been rapidly increased and energy efficient management of LED light system is regarded as an important technology to enhance the energy efficiency. In this paper, we propose an energy-efficient control scheme of LED light, being composed of multiple light sources. The proposed scheme controls the intensity of LED light source to minimize the total intensity while providing the quality of lighting service. The intensity of light is assumed to be proportional to power consumption, thus the objective is to minimize the total power consumption. A linear programming problem is formulated to find the optimal intensity of each light source and procedure to apply the proposed scheme in the real system is suggested. The performance evaluation results elucidate that the proposed scheme achieves over 20% improvement in power consumption of light intensity in comparison with the conventional dimming control scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.490-496
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• 2007

This paper describes the design and implementation of an integrated LTCC front-end module for the IEEE802.11a WLAN applications by performing the behavioral-level simulation using measurement-based behavioral model. To meet the IEEE802.11a WLAN standard, a system transmitting 1024 symbols through 64-QAM process at the rate of 54Mbps should be implemented and nonlinear properties are confirmed by simulations of ACPR and EVM in this circumstance. The right offsets of ACPR which are 30MHz, 20MHz, and 11MHz distant from the center frequency of 5.8GHz are 49.36dBc, 36.90dBc, and 24.58dBc, respectively. The left offsets are 50.14dBc, 30.04dBc, and 28.85dBc, respectively and EVM is 2.94%. The size of the module implemented with LTCC five-layer substrates is $13.4mm{\times}14.2mm$. The measured characteristics of the transmitter show P1dB of 16.2dBm and power gain of 16.73dB. Those of the receiver exhibit the small signal gain of 16.24dB and noise figure of 7.83dB.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.10 s.352
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• pp.111-117
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• 2006

Reconfigurable CMOS low-noise amplifier (LAN) has been developed for multi-mode/multi-band wireless receiver. By employing common-gate input stage, the performance can be optimized for multiple operation bands by simply controlling the output load impedance. Although the conventional common-gate LAN has larger than 3dB noise figure (NF), the newly developed negative feedback scheme enables the common-gate input LNA to have less than 2dB NF. To have optimum linearity performance of wireless receiver, the gain of the LNA can be controlled. The LNA implemented in a 0.13mm CMOS technology shows $19{\sim}20dB$ voltage gain, $1.7{\sim}2.0dB$ NF, -2dBm iIP3 at $1.8{\sim}2.5GHz$ frequency range. The LNA dissipates 7mW from a 1.2V supply voltage.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.106-106
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• 2014

SIGMA (Scientific cubesat with Instrument for Global Magnetic field and rAdiation)는 근 지구공간에서 우주방사선량 측정과 자기장 변화 검출의 과학적 목적과 교육적 목적을 가지고 개발하고 있는 초소형 큐브위성이다. $100mm{\times}100mm{\times}340.5mm$의 크기로 약 3.6 kg의 무게를 가지며, 탑재체는 방사선에 대하여 인체와 동일한 산란 흡수 특성을 가진 Tissue Equivalent Proportional Counter (TEPC)와 자기장 측정을 위한 Magnetometer (Mag)이다. 위성체는 구조계, 자세제어계, 전력계, 명령 및 데이터처리계, 통신계로 구성되어있다. 구조계는 위성의 뼈대인 Chassis와 Mag deployer로 이루어져있고, 위성의 안정적인 자세유지를 목적으로 Attitude Control System (ACS) Board와 Torque Coil이 자세제어계로 구성된다. 전력의 생산과 공급 및 충전은 태양전지판과 Electrical Power System (EPS), 리튬 배터리로 구성된 전력계에서 이뤄지며, 명령 및 데이터처리계는 On Board Computer (OBC)와 Instrument Interface board (IIB)를 중심으로 서브시스템의 명령체계와 데이터처리를 다룬다. 통신계는 Uplink인 VHF 안테나와 Downlink인 UHF, S-band 안테나로 구성되며 지상과 명령을 송수신한다. SIGMA는 타임인터럽트 기능을 활용한 Flight Software (FSW)로 운용되며 임무에 따른 6가지 모드의 시나리오로 위성을 운용한다. 이에 SIGMA의 개발과 테스트 결과를 소개한다. 본 큐브위성 개발기술을 바탕으로 향후 천문관측용 위성에도 활용할 예정이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.352-360
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• 2008

Recently Task Group (TG) 4 of the Institute of Electrical and Electronics Engineers (IEEE) 802.15a has been recommended a system with ranging capability in existence of multiple Simultaneous operating piconets (SOPs) as well as low-cost, low-power. According to the ranging service, coherent and non-coherent based ranging schemes using ternary code have been adopted as a standard. However it is hard to estimate an accurate time of arrival (TOA) in case of using direct sequence based TOA estimation method because pulse repetition interval (PRI) offered by TG is more limited than the maximum excess delay (MED) of channel. To mitigate inter pulse interference (IPI) problem, this paper proposes a non-coherent TOA estimation scheme using non-periodic transmission (NPT) pattern. The proposed receiver is based on a non-coherent energy detection considering with motivation of low rate wireless personal area network (LR-WPAN). TOA information is estimated via proper comparison with a prescribed threshold after the sliding correlation and search back window (SBW) process for reducing TOA error. To verify the performance of proposed ranging scheme, two distinct channel models approved by IEEE 802.15.4a TG are considered. According to the simulation results, we could conclude that the proposed scheme have performed better performance than the conventional method on the existence of multiple SOPs.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.9-17
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• 2010

Recently, there has been much interest in orthogonal frequency division multiplexing (OFDM) for next generation wireless wideband communication systems. OFDM is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarriers. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. However, in the radio systems it is also important to distortion introduced by high power amplifiers (HPA's) such as solid state power amplifier (SSPA) considered in this paper. Since the signal amplitude of the OFDM system is Rayleigh-distributed, the performance of the OFDM system is significantly degraded by the nonlinearity of the HPA in the OFDM transmitter. In this paper, we propose a canonical piecewise-linear (PWL) model based digital predistorter to prevent signal distortion and spectral re-growth due to the high peak-to-average power ratio (PAPR) of OFDM signal and the nonlinearity of HPA's. Computer simulation on an OFDM system under additive white Gaussian noise (AWGN) channels with QPSK, 16-QAM and 64-QAM modulation schemes and modulator/demodulator implemented with 1024-point FFT/IFFT, demonstrate that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinearity introduced by the SSPA.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.56-63
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• 2012

The WBAN technology means a short distance wireless network which provides each device interactive communication by connecting devices inside and outside of body. Standardization on the physical layer, data link layer, network layer and application layer is in progress by IEEE 802.15.6 TG BAN. Wireless body area network is usually configured in energy efficient using sensor and zigbee device due to the power limitation and the characteristics of human body. Wireless sensor network consist of sensor field and sink node. Sensor field are composed a lot of sensor node and sink node collect sensing data. Wireless sensor network has capacity of the self constitution by protocol where placed in large area without fixed position. Mobile sink node distribute energy consumption therefore network life time was increased than fixed sink node. The energy efficient is important matter in wireless body area network because energy resource was limited on sensor node. In this paper we proposed cluster topology algorithm for efficient data transmission in wireless body area network based mobile sink. The proposed algorithm show good performance under the advantage of grid routing protocol and TDMA scheduling that minimized overlap area on cluster and reduced amount of data on cluster header in error prone wireless sensor network based on mobile sink.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.97-102
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• 2020

This paper relates with the Hybrid-SE-MMA (Signed-Error MMA) that is possible to improving the equalization performance by using the adaptive modulus and adaptive step size in SE-MMA adaptive equalizer for the minimizing the intersymbol interference. The equalizer tap coefficient is updatted use the error signal in MMA algorithm for adaptive equalizer. But the sign of error signal is used for the simplification of arithmetic operation in SE-MMA algorithm in order to updating the coefficient. By this simplification, we get the fast convergence speed and the reduce the algorithm processing speed, but not in the equalization performance. In this paper, it is possible to improve the equalization performance by computer simulation applying the adaptive modulus to the SE-MMA which is proposional to the power of equalizer output signal. In order to compare the improved equalization performance compared to the present SE-MMA, the recovered signal constellation that is the output of the equalizer, residual isi, MD(maximum distortion), MSE and the SER perfomance that means the robustness to the external noise were used. As a result of computer simulation, the Hybrid-SE-MMA improve equalization performance in the residual isi and MD, MSE, SER than the SE-MMA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.4
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• pp.211-221
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• 2012

The development of wireless sensor networks (WSNs) is progressed slowly due to limited resources, but it is in progress to the development of the latest IP-based IP-WSN by the development of hardware and power management technology. IPv6 over Low power WPAN (6LoWPAN) is capable of IPv6-built low-power devices. In these IP-based WSNs, existing IP-based techniques which was impossible in WSNs becomes possible. 6LoWPAN is based on the IEEE 802.15.4 sensor networks and is a IPv6-supported technology. Host-based mobility management scheme in IP-WSNs are not suitable due to the additional signaling, network-based mobility management scheme is more suitable. In this paper, we propose an enhanced PMIPv6-based route optimization scheme which consider multi-6LoWPAN network environments. All SLMA (Sensor Local Mobility Anchor) of the 6LoWPAN domain are connected with the SPIG (Sensor Proxy Internetworking Gateway) and performs distributed mobility control for the 6LoWPAN-based inter-domain operations. All information of SLMA in 6LoWPAN domain is maintained by SMAG (Sensor Mobile Access Gateway), and then is performed the route optimization quickly. The status information of the route optimization from SPIG is stored to SLMA and it is supported without additional signaling.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.11-16
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• 2012

Opportunistic transmit cooperative relaying (OTR) system has been interested for its ability to mitigate the fading in wireless channel without multiple antennas in a small terminal. In OTR system, only the relays that the received Signal-to-noise ratio (SNR) from a source is greater than the threshold transmit to the destination. However, the receiving branches of a destination in a realistic system is fixed, the excess number of signals from the transmit relays does not improve the system performance and consequently increases power consumption. In this paper, we adopt Double Opportunistic Transmit (DOT) cooperative diversity system which controls the average number of transmit relays. Although the average number of the transmit relays can be controlled by adjusting the two thresholds in DOT system, the instantaneous number of transmit relays is varying in fading channel. Thus we propose Maximal Ratio Combining (MRC) or Generalized Selection Combining (GSC) according to the number of the signals from relays at the destination. The outage probability of the proposed system is derived in closed form. The analytical results show that the system performance is improved with the number of the branches. Also it is noticed that when the number of the branches is fixed, the outage probability decreases with the increase of the average SNR of S-R path and R-D path.