• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.357-360
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• 2013

A 1.8V 2-Gb/s scalable low voltage signaling (SLVS) transmitter (TX) is designed for mobile applications requiring high speed and low power consumption. It consists of 4-lane TX for data transmission, 1-lane TX for a source synchronous clocking, and a 8-phase clock generator. The proposed SLVS TX has the scaling voltage swing from 50 mV to 650 mV and supports a high speed (HS) mode and a low power (LP) mode. An output impedance calibration scheme for the SVLS TX is proposed to improve the signal integrity. The proposed SLVS TX is implemented by using a $0.18-{\mu}m$ 1-poly 6-metal CMOS with a 1.8V supply. The simulated data jitter of the implemented SLVS TX is about 8.04 ps at the data rate of 2-Gbps. The area and power consumption of the 1-lane of the proposed SLVS TX are $422{\times}474{\mu}m^2$ and 5.35 mW/Gb/s, respectively.

• Journal of Satellite, Information and Communications
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• v.8 no.1
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• pp.31-34
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• 2013

This paper deals with the interfering audio noise caused by LTE(Long Term Evolution) UE(User Equipment) which is 4th generation mobile communications on audio devices. At first, we realized that the interfering signal of the LTE UE is determined by the transmit power of the LTE UE through analysis and measurement. Then, we performed to measure audio noise level according to the variation of transmitting power level and separation distance between the LTE UE and an audio device. As a result, it is required that minimum separation distance should be 25 cm and above in order to protect audio device from the interference noise of the LTE UE with the maximum transmit power level of 22 dBm.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.8
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• pp.3-9
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• 2015

Under the maximum transmit power constraint and the minimum rate constraint, we propose the optimal number of transmit antennas and transmit power which maximize energy-efficiency (EE) in multi-user multiple-input multiple-output (MIMO) downlink system with the maximal ratio transmission (MRT) precoding. Because the optimization problem for the instantaneous channel is difficult to solve, we use independence of individual channel, average channel gain and path loss to approximate the objective function. Since the approximated EE optimization problem is two-dimensional search problem, we find the optimal number of transmit antennas and transmit power using Lagrange multipliers and our proposed algorithm. Simulation results show that the number of transmit antennas and power obtained by proposed algorithm are almost identical to the value by the exhaustive search.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.50-51
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• 2011

In a radar system using a continuous waveform, the separated antennas are needed for transmission and reception to increase the sensitivity of the receiver channel. Even for these separated antennas, the serious intereference in the weak echo signal can occur due to the relatively strong power of the transmitted waveform. Therefore, in this paper, the effects of this leakage interference on the receiving signal are analyzed according to the degree of antenna isolation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2B
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• pp.137-144
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• 2002

In this paper, we optimize the base station placement and transmission power using genetic approach. A new representation describing base station placement and transmit power with real number is proposed, and new genetic operators are introduced. This new representation can describe the locations, powers, and number of base stations, Considering coverage, power and economy efficiency, we also suggest a weighted objective function. Our algorithm is applied to an obvious optimization problem, and then it is verified. Moreover, our approach is tried in inhomogeneous traffic distribution. Simulation result proves that the algorithm enables to fad near optimal solution according to the weighted objective function.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.854-861
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• 2008

We have described a high power hybrid envelope elimination and restoration(H-EER) transmitter for IEEE 802.16e Mobile World Interoperability for Microwave Access(WiMAX) using an efficiency optimized power amplifier(PA). The PA has been designed to have maximum PAE at the important power generation $V_{ds}$, region using Nitronex 100-W PEP GaN HEMT. For the high power application, H-EER transmitter should be considered the regenerative oscillation problem due to the PA's bias fluctuation effect and bias modulator stability issue. Therefore, the bias modulator for H-EER transmitter has been designed to suppress the regenerative oscillation. For the interlock experiment, the bias modulator has been built with the efficiency of 72% and peak output voltage of 30 V for the envelope signal with a PAPR of 8.5 dB. The H-EER transmitter for WiMAX application has been achieved a high PAE characteristic, 38.8 % at an output power of 41.25 dBm. By using digital predistortion(DPD) technique, the Relative Constellation Error (RCE) has been satisfied the specification of -34.5 dB. This is the first work at 2.655 GHz high power H-EER transmitter for WiMAX application.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.31-39
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• 2007

In this paper, a system for real-time or periodic measurement and analysis of RF parameters such as forward transmit power and pilot power in CDMA base station systems is proposed. Such RF characteristic parameter measurement can be prevented from system fault and used to achieve optimal service quality and maximum investment return through cell coverage expansion, subscriber capacity increase and so on. For forward power measurement, the local oscillator frequency for the detector is varied so that the transmit power for all channels can be measured. The channel power measurement can be used to analyze the variation in transmit power for changes in voice traffic. By comparing to forward $E_c/I_o$, the pilot channel power can be deducted, which can be used to determine uy degradation in transmit section modules such as the high dover amplifier. Since an accurate analysis of carefully measured data using the CDMA level detector must be made, the system is designed so that measurement errors due to changes in crest factor with modulation method can be overcome.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.12
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• pp.2219-2225
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• 2016

Mobile communication systems should be able to support multimedia traffics with limited transmit power due to the frequency reuse for maximizing the channel accommodation. Real-time data is very sensitive to delay, and they need to be transmitted instantly. On the other hand, non-real time data is less sensitive to delay, and their packet loss can be handled more flexibly. Therefore an adaptive resource management scheme is essentially required which enables to keep the minimal power allocated in the base station while guaranteeing the user requirements for QoE within a permissible range. Power-saving techniques are required in order to support multimedia services in the mobile networks because the power consumption increases greatly with the transmission rate increase. This paper proposes a novel scheme which enables to keep the allocated power minimal while guaranteeing the user requirements for QoE within a permissible range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.237-241
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• 2002

전력선과 조명등을 이용한 음향전달 시스템을 구성하여 어학실습 교육용으로의 활용 가능성을 평가하였다. 음성신호를 변조하여 전력선에 실어 보내는 송신기와 조명등의 빛으로부터 음성신호를 검출하여 이어폰 또는 헤드폰 둥으로 들을 수 있는 수신기로 구성하였다. 제작한 송신기와 수신기의 주파수 특성과 스펙트럼분석을 하였다. 스피커로 출력되는 음질상태는 최적상태는 아니지만 음성이나 노래 등을 이용한 어학실습 교육용으로는 충분한 수준이 었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.974-983
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• 2007

In this paper, a low complexity subcarrier allocation scheme is proposed for multiuser MIMO-OFDM systems with zero-forcing beamformer (ZFBF) so that the total transmit power can be minimized satisfying given target data rate. Since the optimal method requires very high computational complexity, we propose a low complextiy suboptimal method. Using the fact that the effective channel gain is proportional to the orthogonallity of channels of multiplexed users, a user set with the highest orthogonality of channel among users is assigned to each subcarrier in order to minimize required transmit power. The numerical results show that the proposed suboptimal method can reduce computational complexity with little performance loss.