• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1248-1255
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• 2005

We investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz bandchannel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. In this paper, we apply phase noise suppression (PNS) algorithm that is easy for implementation to OFDM based 60 GHz wireless LAM system and analyze the SER performance. In case of using the PNS algorithm, SER performance is improved about 6dB, 7.5dB, respectively in 16, 64-QAM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.3
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• pp.280-292
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• 1989

In this paper, the error rate equations of digitally modulated signals transmitted through the channel which is not only Gaussian/Impulsive noise but also multi-path fading have been derived. Using the derived equations for the error probabilities of ASK, QAM, CPSK, DPSK, FSK, and MSK signals, the error rate performances of digital modulation systems have been evaluated and represented in the graphs as the functions of CNR, Impulsive indes, the ratio of Gaussian noise power component to Impulsive noise power component, and fading figures. The results show that, in the deep fading environment, the error is occurred more frequency by Gaussian noise than Impulsive noise. And the comparison of various systems certifies that PSK is superior to the ohter systems in the deep fading or shallow fading environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.963-972
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• 2002

An 8192-point pipelined FFT/IFFT processor core is designed, which can be used in multi-carrier modulation systems such as DUf-based VDSL modem and OFDM-based DVB system. In order to improve the signal-to-quantization-noise ratio (SQNR) of FFT/IFFT results, two-step convergent block floating-point (TS_CBFP) scaling is employed. Since the proposed TS_CBFP scaling does not require additional buffer memory, it reduces memory as much as about 80% when compared with conventional CBFP methods, resulting in area-and power-efficient implementation. The SQNR of about 60-㏈ is achieved with 10-bit input, 14-bit internal data and twiddle factors, and 16-bit output. The core synthesized using 0.25-$\mu\textrm{m}$ CMOS library has about 76,300 gates, 390K bits RAM, and twiddle factor ROM of 39K bits. Simulation results show that it can safely operate up to 50-㎒ clock frequency at 2.5-V supply, resulting that a 8192-point FFT/IFFT can be computed every 164-${\mu}\textrm{s}$. It was verified by Xilinx FPGA implementation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1395-1401
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• 2004

In The objective of this paper is to apply blind minimum output energy multiuser detection method to multicarrier direct sequence code division multiple access system. The performance of MC/DS-CDMA is reduced due to multiple access. To increase the performance of system, we need to cancel multiple user components. Blind interference canceller is able to detect the desired's information with the only minimal information of the desired user. We evaluate the performance of the proposed receiver under Gaussian channel. Simulation results show that the proposed receiver has about 6［dB］ gain of signal to noise ratio without multiple user interference and has about 3［dB］ gain of SNR with multiple user interference. Also, the result of comparing the capacity of the active users shows that the proposed method has about 2 times capacity more than conventional method. As a conclusion, simulation results show that the proposed method has better performs better than conventional method.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.241-241
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• 2020

축산물의 수요가 증가함에 따라 가축의 사육규모 및 두수도 증가하여 가축분뇨의 발생량이 증가한다. 가축분뇨는 일반하수에 비해 고농도의 유기물, 질소, 인 등의 오염물질이 포함되어 있다. 적절한 처리 없이 하수처리장 및 수계로 유입될 경우 하수처리장 처리 효율에 영향을 미치거나 부영양화 등 다양한 문제를 야기 시킬 수 있다. 이러한 문제를 해결하기 위해 아질산화 반응을 이용하는 다양한 공정들이 연구되고 있다. 아질산화 반응은 완전 질산화 반응에 비해 질산화 단계에서 약 25%의 산소요구량이 절감되고, 탈질 단계에서 약 40%의 탄소원이 절감되는 경제적 장점이 있기 때문이다. 본 연구에서는 부피 8L의 실험실 규모 아질산화 반응조 원통형 아크릴로 제작되었고, 서울 A하수처리장 미생물을 채취하여 사용했다. 또한 SRT의 영향을 살펴보기 위하여 35℃ 동일 온도를 유지했다. 반응조 슬러지 반송 및 폐기가 없는 완전 혼합 반응조로 SRT와 HRT가 동일하게 운전하는 방법을 사용하여 SRT를 조절하는 방식으로 운전했다. SRT의 경우 8일, 6일, 4일, 2일의 변경조건을 통해서 차이를 살펴보았다. Ammonia Removal Rate(%)의 경우 각각 86%, 86%, 87%, 24%의 효율을 보였고, Nitrite Conversion Rate(%)의 경우 각각 10%, 45%, 80%, 41%의 효율을 보였다. 35℃ 실험실 규모 반응조에서 가축분뇨 유입 원수의 아질산화 반응을 유도하기 위해서는 SRT운전 조건은 4~8일, 고효율의 아질산화 반응을 유도하기 위해서는 SRT 4일 조건이 적합하다고 판단된다. 본 연구는 실제 가축분뇨 처리 효율 상승을 위해서 아질산화 공법을 도입할 경우 중요한 자료로 이용 가능할 것으로 판단된다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.562-573
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• 2006

It is required to reduce the peak-to-average power ratio(PAPR) in an orthogonal frequency division multiplexing system or a multicarrier system. And it is needed to eliminate the transmission of the side information in the Partial Transmit Sequences. So, in this paper, a new technique is proposed, where the subcarriers used for the multiple signal representation are only utilized for the reduction of PAPR to eliminate the burden of transmitting the side information. That is, it is proposed by taking the modified minimization criteria of partial transmit sequences scheme instead of using the convex optimization or the fast algorithm of tone reservation(TR) technique As the result of simulation, the PAPR reduction capability of the proposed method is improved by 3.2 dB dB, 3.4 dB, 3.6 dB with M=2, 4, 8(M is the number of partition in the so-called partial transmit reduction sequences(PTRS)), when the iteration number of fast algorithm of TR is 10 and the data rate loss is 5 %. But it is degraded in the capability of PAPR reduction by 3.4 dB, 3.1 dB, 2.2 dB, comparing to the TR when the data rate loss is 20 %. Therefore, the proposed method is outperformed the TR technique with respect to the complexity and PAPR reduction capability when M=2.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.1
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• pp.121-132
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• 2000

This study is to investigate the performance of a new BNR process using predenitrification scheme focusing on nitrogen removal and the possibility of adapting a computer simulation scheme in BNR process development. By using a pre-denitrification basin, higher $COD/NO_3-N$ ratio could be sustained in this BNR process. The results of the investigation showed a SDNR value of 9.04mg/gMv/hr. In the anoxic tank, the average value of SPRR of 6.25mgP/gMv/hr was observed to be very sensitive to SCOD load of influents. By calibrating internal parameters (stoichiometric and kinetic parameters) of the simulation model, the results of simulation for various BNR processes gave good agreement with observed data. The major adjustment was given with three parameters, maximum specific growth rate of heterotrophic biomass, short chain fatty acid (SCFA) limit, and phosphorous release rate. With the series of simulations on varying operational conditions, the simulation by computer program can be a useful tool for process selection, and design and operation of municipal wastewater treatment plant.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.9
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• pp.28-34
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• 2002

In this paper, a new type predistorter using a low frequency intermodulation signals terms of harmonic generator is proposed. A vector modulator, in which fundamental signal is modulated with low frequency intermodulation signals derived from harmonic generator, generates predistorted third and fifth IM components. Using predistorted signals, intermodulation distortion signals of power amplifier suppressed. The suggested predistorter has been manufactured to operate in Korean PCS base-station transmitting band (1840~1870MHz). The test results show that the third IMD signal level is reduced more than 20dB and the fifth IMD signal is reduced about 10dB for CW two-tone signals. The predistorter improves the Adjacent Channel Power Ratio (ACPR) more than 10dB for CDMA (IS-95) signals.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.10
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• pp.26-36
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• 2000

In this paper, we design the nonoverlapping multicarrier modulation (MCM) system for high rate paging system and evaluate the Performance by computer simulation. In conventional paging system, FSK was usually used, but we select QAM for high bandwidth efficiency. Transmitter structure adopts that of 4-16QAM of the iDEN$\^$TM/ and receiver consists of symbol timing recovery, carrier recovery and automatic gain control. In addition, pilot symbol aided modulation (PSAM) which can overcome the simulcast fading channel is considered and we also propose the optimum pilot symbol pattern. Finally, we show the performance of the overall 4-16QAM system by computer simulation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.770-776
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• 2009

We propose and demonstrate an I/Q demodulator using four-port BPSK demodulator base on additive mixing and reflection-type phase shifter using hybrid technique. Previously, the conventional I/Q demodulator base on multiplicative or additive mixing method divides I/Q signal path from mixer to parallel-to-serial converter. In this paper, we propose new I/Q demodulator without dividing I/Q baseband signal path. The proposed schematic requires half size in implementation and half power consumption in baseband path compared with the conventional receiver. Also, the proposed receiver eliminates parallel-to-serial converter after data decoding. The proposed circuit has been successfully demodulated a QPSK signal with the L-band carrier frequency and 20 Mbps data rate.