• Journal of Electrical Engineering and Technology
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• 제13권2호
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• pp.943-952
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• 2018

This paper presents a new type of absolute rotary encoder system based on the affine n-digit N-ary gray code. A brief comparison of the existing encoder systems is carried out in terms of resolution, encoding and decoding principles and number of sensor heads needed. Using the proposed method, two different types of encoder disks are designed, namely, color-coded disk and grayscale coded disk. The designed coded disk pattern is used to manufacture 3 digit 3 ary and 2 digit 5 ary grayscale coded disks respectively. The manufactured disk is used with the light emitter and photodetector assembly to design the entire encode system. Experimental analysis is done on the designed prototype with LabVIEW platform for data acquisition. A comparison of the designed system is done with the traditional binary gray code encoder system in terms of resolution, disk diameter, number of tracks and data acquisition system. The resolution of the manufactured system is 3 times higher than the conventional system. Also, for a 5 digit 5 ary coded encoder system, a resolution approximately 100 times better than the conventional binary system can be achieved. In general, the proposed encoder system gives $(N/2)^n$ times better resolution compared with the traditional gray coded disk. The miniaturization in diameter of the coded disk can be achieved compared to the conventional binary systems.

• 한국군사과학기술학회지
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• 제11권5호
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• pp.23-33
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• 2008

In this paper, we verify the performance of LDPC coded OFDM/DS system by Monte-Carlo simulation of BER on Eb/No. The simulation results show that LDPC coded OFDM/DS has a strong anti-jamming characteristic over pulse-noise jammer and partial-band noise jammer. The performance of LDPC coded OFDM/DS system is evaluated on both faded waveforms and non-faded waveforms. For non-faded waveforms, high coding gain is attained due to LDPC, even when waveforms have short PN sequence and JSR is only 5dB. Especially, the increase in the repeated number of LDPC decoding enhances coding gain. However, faded waveforms cannot achieve sufficient average effect when PN sequence is short. High coding gain of faded waveforms can be achieved by extending length of PN sequence. In addition, we compare LDPC coded OFDM/DS system with Convolutional coded OFDM/DS system. The simulation results illustrate that when LDPC coded OFDM/DS system with short PN sequence has sufficient average effects, the system shows lower BER than Convolutional coded OFDM/DS system with long PN sequence.

• 산업경영시스템학회지
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• 제28권3호
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• pp.149-155
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• 2005

In this paper, we optimize simulation model of a manufacturing system using the real-coded genetic algorithm. Because the manufacturing system expressed by simulation model has stochastic process, the objective functions such as the throughput of a manufacturing system or the resource utilization are not optimized by simulation itself. So, in order to solve it, we apply optimization methods such as a genetic algorithm to simulation method. Especially, the genetic algorithm is known to more effective method than other methods to find global optimum, because the genetic algorithm uses entity pools to find the optimum. In this study, therefore, we apply the real-coded genetic algorithm to simulation optimization of a manufacturing system, which is known to more effective method than the binary-coded genetic algorithm when we optimize the constraint problems. We use the reproduction operator of the applied real-coded genetic algorithm as technique of the remainder stochastic sample with replacement and the crossover operator as the technique of simple crossover. Also, we use the mutation operator as the technique of the dynamic mutation that configures the searching area with generations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.233-235
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• 2005

As a class of block codes, LDPC code with any desired code rate and code length is easily constructed. In OFDM system high data transmission is possible, In this paper, we examined the performance of four high-rate(0.75, 0.8, 0.889, 09412) LDPC coded OFDM in image transmission over Rayleigh fading channel. The high-rate of 0.9412 LDPC coded OFDM system obtained about 12dB gain over the OFDM at BER of $10^{-3}$ over Rayleigh fading channel. Also, the PSNR of code rate 0.9412 LDPC coded OFDM system at SNR=10dB is given by 18.8047dB where uncoded OFDM system gives 9.7303 dB.

• 전자공학회논문지
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• 제50권8호
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• pp.21-27
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• 2013

본 논문에서는 Turbo coded BICM-ID (bit-interleaved coded modulation with iterative decoding)의 구현 복잡도를 개선하기 위한 기법을 제안한다. 터보 부호는 Shannon 한계에 근접하는 우수한 성능을 나타내는 오류정정부호 (error correction code)이며 터보 부호와 고차원 변조 (high order modulation)를 결합하여 전송효율을 개선할 수 있다. BICM (bit-interleaved coded modulation)은 채널 부호와 고차원 변조 사이에 이진 인터리버를 사용하는 기법이며 복호기와 복조기 간에 정보를 주고받으며 반복 복호 (iterative decoding)를 수행하는 BICM-ID를 이용하여 성능을 개선 할 수 있다. BICM-ID는 BICM과 비교하였을 때 반복 복호로 인하여 비트오율 (bit error rate) 성능이 개선되지만 구현 복잡도가 크게 증가하는 단점이 있다. 본 논문에서는 Turbo coded BICM-ID에서 구현 복잡도를 개선하기 위한 기법을 제안한다. 제안하는 기법은 기존에 제안된 Turbo coded BICM-ID 기법과 유사한 비트오율 (bit error rate) 성능을 나타내면서 구현 복잡도를 크게 감소시킬 수 있는 장점이 있다.

• 한국통신학회논문지
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• 제25권3A호
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.199-207
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• 2021

This paper deals with accurate image reconstruction of gamma camera using a coded-aperture mask based on pixel-type CsI(Tl) scintillator coupled with silicon photomultipliers (SiPMs) array. Coded-aperture imaging (CAI) system typically has a smaller effective viewing angle than Compton camera. Thus, if the position of the gamma source to be searched is out of the fully-coded field-of-view (FCFOV) region of the CAI system, artifacts can be generated when the image is reconstructed by using the conventional cross-correlation (CC) method. In this work, we propose an effective method for more accurate reconstruction in CAI considering the source distribution of partially-coded field-of-view (PCFOV) in the reconstruction in attempt to overcome this drawback. We employed an iterative algorithm based on compressed-sensing (CS) and compared the reconstruction quality with that of the CC algorithm. Both algorithms were implemented and performed a systematic Monte Carlo simulation to demonstrate the possiblilty of the proposed method. The reconstructed image qualities were quantitatively evaluated in sense of the root mean square error (RMSE) and the peak signal-to-noise ratio (PSNR). Our simulation results indicate that the proposed method provides more accurate location information of the simulated gamma source than the CC-based method.

• 한국공간정보시스템학회 논문지
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• 제5권2호
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• pp.83-89
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• 2003

본 연구에서는 차량측량시스템에 사용할 수 있는 코드(Coded) 타겟을 설계, 제작하고 이를 자동으로 식별하고 타겟 중심의 영상좌표를 획득하는 방법을 개발하였다. 차량측량시스템은 CCD, GPS, INS 장비를 통합 탑재하여 도로상에 존재하는 시설물과 노면에 대한 3차원 정보를 획득할 수 있는 시스템이다. 차량측량시스템은 특성상 카메라 검교정과 외부표정을 위해서 미리 설치된 타겟을 사용하며 표정작업을 위한 영상좌표 획득은 수동에 의한 방법이 사용되어 왔다. 그러나 코드 타겟을 사용하며 타겟의 자기인식(Self-Identifying)을 통해 각 영상에서 관측된 타겟을 하나의 공액점으로 인식 가능하고 자동으로 타겟 중심의 영상점 획득이 가능하다. 이처럼 자동화된 타겟 관측 및 영상점 획득이 가능하다면 차량측량시스템의 카메라 검교정 및 외부표정을 작업의 효율성을 향상시키고 영상좌표 획득의 일관성을 유지하는데 매우 효과적일 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1259-1265
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• 2021

In the present study, a large-area hybrid gamma imaging system was designed by adopting coded aperture imaging on the basis of a large-area Compton camera to achieve high imaging performance throughout a broad energy range (100-2000 keV). The system consisting of a tungsten coded aperture mask and monolithic NaI(Tl) scintillation detectors was designed through a series of Geant4 Monte Carlo radiation transport simulations, in consideration of both imaging sensitivity and imaging resolution. Then, the performance of the system was predicted by Geant4 Monte Carlo simulations for point sources under various conditions. Our simulation results show that the system provides very high imaging sensitivity (i.e., low values for minimum detectable activity, MDA), thus allowing for imaging of low-activity sources at distances impossible with coded aperture imaging or Compton imaging alone. In addition, the imaging resolution of the system was found to be high (i.e., around 6°) over the broad energy range of 59.5-1330 keV.

• 한국전자파학회논문지
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• 제9권4호
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• pp.427-438
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• 1998

본 논문에서는 동일채널간섭과 라이시안 페이딩 환경에서 Trellis Coded QPSK 시스템의 BER 생능올 분석 하였다. 고려되는 Trellis Coded QPSK 시스템은 시스템의 성능을 향상시키기 위하여 최대비 합성(MRC) 다이버시티 수신법과 Reed-Solomon 부호를 사용하였다. 유도한 오율식을 이용하여 Trellis 부호화된 QPSK 시스템의 성능을 구하여, 신호 전력 대 잡음 전력비 (SNR), 신호 전력 대 간섭파의 전력비 (SIR), 라이시안 페이딩 파라미터 (KR), MRC 다이버시티의 가지수 (M), Reed-Solomon 부호의 천체 블럭 길이 (n), Reed-Solomon 부호의 정정 가능한 심볼의 수 (t), Trellis 부호기의 상태수를 함수로 하여 그래프로 나타내고 분석하였다. 분석결과, 제안하는 시스템의 성능은 마이크로셀 환경에서 동일채널간섭과 페이딩에 의하여 영향을 받음을 알 수 있었다. 또한 희망하는 신호의 전력이나 신호 전력 대 간섭파의 전력비를 증가시켜 Trellis 부호화된 QPSK 시스템의 BER 성능을 개선할 수 있음을 알 수 있었다. 그리고 마이크로 셀룰러 시스템의 BER floor 현상은 동 일채널간섭에 의하여 발생하고, 이 현상은 신호 전력 대 간섭와의 전력배가 낮은 경우에는 높은 BER에서 발생 함을 알 수 있었다. 그리고 통일채널간섭과 라이시안 페이딩의 영향올 억압하기 위해서는 M=2인 MRC 다이버 시티 수신된 Trellis Coded QPSK 시스댐보다는 t=2, n=15인 Reed-Solomon 부호롤 척용한 Trellis Coded QPSK 시스템이 효율적임을 알 수 있었다.