• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.697-703
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• 2013

We propose an efficient frequency-time domain resource allocation scheme in multi-carrier (MC) direct-sequence code-division multiple-access (DS/CDMA) communications. We consider, as a power allocation strategy in the frequency domain, transmitting each user's DS waveforms over the user's sub-band with the largest channel gain. We then consider rate adaptation in the time domain, where the data rate is adapted such that a desired transmission quality is maintained. We analyze the achievable average data rate of the proposed scheme with fixed average transmission power, and compare the performance to single carrier DS/CDMA systems with power and rate adaptations.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.651-658
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• 2001

A novel multi-section power divider configuration is proposed to obtain wide-band frequency performance up to microwave frequency region. Design procedures for the proposed microwave broadband power divider are composed of a planar multi-section three-ports hybrid and a waveguide transformer design procedures. The multi-section power divider is based on design theory of the optimum quarter-wave transformer. Furthermore, in order to obtain the broadband isolation performance between the two adjacent output ports, the odd mode equivalent circuit should be matched by using the lossy element such as resistor. The derived design formula for calculating these odd mode matching elements is based on the singly terminated filter design theory. The waveguide transformer section is designed to suppress the propagation of the higher order modes such as waveguide modes due to employing the metallic electric wall. Thus, each section of the designed waveguide transformer should be operated with evanescent mode over the whole design frequency band of the proposed microwave broadband power divider. This paper presents several simulations and experimental results of multi-section power divider to show validity of the proposed microwave broadband power divider configuration. Simulation and experiment show excellent performance of multi section power divider.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.4
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• pp.673-677
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• 2016

In this study, In order to measure foot pressure, it makes analyzing device using multi-pressure sensor. This device was limited frequency band to 5Hz by using low-pass filter and MCU was detected signal every milliseconds. After wearing the device, the result was confirmed by blue-tooth to measure wirelessly. Also, we propose an algorithm to obtain the walking pattern using a time table in each of the detected peak from the pressure sensor. Using the algorithm, right walking pattern and abnormal pattern was detected. The results can be reflected more individual walking patterns than when using a conventional methods and also, developed device was no restriction on the human activity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.410-413
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• 2001

In this paper, we present results of this that design of the multi-layer VCO(Voltage Controlled Oscillator), which is composed of the resonation circuit and the oscillation circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for acquiring EM(Electromagnetic) characteristics of conductor pattern as well as designing multi-layer VCO, Acquired EM characteristics of the circuit pattern was used like real components at nonlinear RF circuit simulator. Finally VCO is simulated at nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was DuPont #9599, which is applied for L TCC process. The structure is constructed with 4 conducting layer. Simulated results showed that the output level was about 1[dBm], the phase noise was 102 [dBc/Hz] at 30[kHz] offset frequency, the harmonics -8dBc, and the control voltage sensitivity of 30[MHz/V] with a DC current consumption of l0[mA]

• Journal of the Korean Society for Aviation and Aeronautics
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• v.21 no.1
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• pp.15-22
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• 2013

In oceanic flight routes, HF radio and satellite data links have weather restrictions, long propagation delay and low data throughput. In this paper, we propose oceanic aeronautical communications scheme in the VHF band based on ad-hoc communication. The proposed scheme organizes autonomously a multi-hop network that is divided into multiple local network using aircraft to fly long-distance communication and supports a hybrid type of multiple access, which consists of random access and TDMA (Time Division Multiple Access) scheme. In addition, several algorithms to apply spatial reuse of transmission to multi-hop long range communication environments have been proposed. The proposed system proves performance improvement on delay time as an effective solution to communicate end-to-end on the oceanic flight routes and strengthens the reliability of oceanic aeronautical communication.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.23-29
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• 1995

In this study, Active noise controlis implemented with single channel and multi-channel adaptive algorithm in 3 dimensional reverberant enclosure sound. field, which occurrs in complicated acoustic mode. First, for the one case excited with the resonant frequency of an enclosure, a target of control and the other cases excited with band-pass filtered random noise(100~400Hz), it is implemented to control reducing interior noise of enclosure with single channel and realtime multi-channel adaptive algorithm for global noise reduction in enclosure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1641-1647
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• 2000

This paper presents an analysis of coverage and capacity for the multi-layer CDMA cellular system. The multi-layer CDMA system that shares a common frequency band consists of macrocells for outdoor users and picocells for indoor users. Though macrocells and picocells interfere with each other the capacity of the whole system can be increased, We have analyzed the effect of muual interference upon cell coverage soft handover areas and capacities. The parameters involved in the engineering of the system are discussed. The study results sow that we can control the service coverage of indoor picocells with the system parameters set properly. It is also show that the capacity of the whole system that the capacity of the whole system can be enhanced smoothly by deploying the indoor picocells within existing macrocells.

• ETRI Journal
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• v.23 no.3
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• pp.121-128
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• 2001

In this paper, the theoretical as well as experimental results of BER characteristics of three different modulation schemes, ASK, FSK and BPSK, in a multi-path Rician channel are addressed. These BER characteristics are analyzed as a function of $E_b/N_o$ and the power ratio of the line of sight (LOS) component to the Rayleigh scattered component. The theoretical as well as computer simulation results shows the ASK is the most suitable modulation scheme for the dedicated short range communication (DSRC) in terms of implemental cost and system complexity. The decision feedback equalizer is proved to be very effective in canceling the multi-path interference in the DSRC channel environment. The simulation result of the equalized ASK, reveals the performance enhancement achievable with decision feedback (DFE) equalizer for the first generation DSRC system. The multi-ray DSRC channel model is also provided to predict the received carrier power and fluctuation, which are quite dependent on the surroundings of a cell.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.410-413
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• 2001

In this paper, we present results of this that design of the multi-layer VCO(Voltage Controlled Oscillator), which is composed of the resonation circuit and the oscillation circuit, using EM simulator and nonlinear RF circuit simulator. EM simulator is used for acquiring EM(Electromagnetic) characteristics of conductor pattern as well as designing multi-layer VCO, Acquired EM characteristics of the circuit pattern was used like real components at nonlinear RF circuit simulator. Finally VCO is simulated at nonlinear RF circuit simulator. The material for the circuit pattern was Ag and the dielectric was Dupont ＃9599, which is applied for LTCC process. The structure is constructed with 4 conducting layer. Simulated results showed that the output level was about 1[dBm], the phase noise was 102 [dBc/Hz] at 30[kHz] offset frequency, the harmonics -8dBc, and the control voltage sensitivity of 30[MHz/V] with a DC current consumption of 10[mA].

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.613-623
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• 2000

Digital TV tuner for 8-VSB modulation was developed with satisfying the requirements of ATSC. The double frequency conversion and the active tracking filter in the front-end were used to reduce interference of the adjacent channels and multi-channels, which suppress If beat and image band. However, it was impossible to get frequency mapping between tracking filter and first VCO(Voltage Controlled Oscillator) in the double conversion digital TV tuner differing from conventional NTSC tuner. This paper, therefore, suggests the available structure and a new method for automatic frequency selection by obtaining the mapping of frequency characteristic over tracking voltage and the combined hardware which compose of Micro-controller, EEPROM, D/A(Digital-to-Analog Converter), OP amp and switch driver to solve above problems.