• Title/Summary/Keyword: Fourier Sine Transform

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Orthogonal variable spreading factor encoded unmanned aerial vehicle-assisted nonorthogonal multiple access system with hybrid physical layer security

  • Omor Faruk;Joarder Jafor Sadiqu;Kanapathippillai Cumanan;Shaikh Enayet Ullah
    • ETRI Journal
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    • v.45 no.2
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    • pp.213-225
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    • 2023
  • Physical layer security (PLS) can improve the security of both terrestrial and nonterrestrial wireless communication networks. This study proposes a simplified framework for nonterrestrial cyclic prefixed orthogonal variable spreading factor (OVSF)-encoded multiple-input and multiple-output nonorthogonal multiple access (NOMA) systems to ensure complete network security. Various useful methods are implemented, where both improved sine map and multiple parameter-weighted-type fractional Fourier transform encryption schemes are combined to investigate the effects of hybrid PLS. In addition, OVSF coding with power domain NOMA for multi-user interference reduction and peak-toaverage power ratio (PAPR) reduction is introduced. The performance of $\frac{1}{2}$-rated convolutional, turbo, and repeat and accumulate channel coding with regularized zero-forcing signal detection for forward error correction and improved bit error rate (BER) are also investigated. Simulation results ratify the pertinence of the proposed system in terms of PLS and BER performance improvement with reasonable PAPR.

Jamming Signal Rejection Algorithm for Uplink of Unmanned Aerial System (무인항공시스템의 상향링크를 위한 재밍신호 제거기법)

  • Lee, Yong-Wook
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.2
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    • pp.182-188
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    • 2018
  • In order to increase the robustness of the uplink for UAS(Unmanned Aerial System), we propose a jamming signal rejection algorithm. In the UAS datalink system, DSSS (direct sequence spread spectrum) is used to reduce the radio noise or jamming signal. In general, jamming signals below the spreading gain are recoverable but the signals beyond the spreading gain can not be recovered. In this paper, these jamming signals beyond spreading gain are detected using the threshold detector in the spectrum area then, generate the estimated signals from the sine wave generator. Finally, we obtain the desired signal to remove jamming signals from the received signals. The proposed scheme can eliminate jamming signals while minimizing the hardware complexity and the original signal loss.

Effect of Shape Error of an Air Stage on Motion Precision (공기 스테이지의 형상 오차가 운동정밀도에 미치는 영향)

  • Ryu, Daewon;Lee, Jae Hyeok;Park, Sang-Shin;Kim, Gyu Ha
    • Tribology and Lubricants
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    • v.36 no.2
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    • pp.68-74
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    • 2020
  • In this study, the effect of the shape error of a guideway on the movement of a stage that uses an air bearing is analyzed. The shape error of moving parts supported by the air bearing is known not to affect the vibrations of moving parts as much as the magnitude of the shape error. This is called the "averaging effect." In this study, the effect of shape error on a guideway, as well as the averaging effect of an air-bearing system, is analyzed theoretically using a dynamic-analysis program. The dynamic-analysis program applies a commercially available code in COMSOL and solves the Reynolds equation between the stage and the guideway, along with the equation of motion of the stage. The stage is modeled as a two-degree-of-freedom system. The shape error is applied to the film thickness function in the form of a sine wave. The stage movement is analyzed using the fast Fourier transform process. The eccentricity and tilting are found to be proportional to the amplitude of the shape error of the guideway. Stage vibrations are less than 10% of the amplitude of the shape error on the guideway. This means that the averaging effect of the air bearing is verified quantitatively. Moreover, if the air supply position matches the shape error in the guideway, there is a notable change in eccentricity and tilting.

Analog-to-Digital Converter using Pipelined Comparator Array (파이프라인드식 비교기 배열을 이용한 아날로그 디지털 변환기)

  • Son, Ju-Ho;Jo, Seong-Ik;Kim, Dong-Yong
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.37 no.2
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    • pp.37-42
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    • 2000
  • In this paper, The high-speed, low-Power analog-to-digital conversion structure is proposed using the pipelined comparator away for high-speed conversion rate and the successive- approximation structure for low-power consumption. This structure is the successive-approximation structure using pipelined comparator array to change the reference voltage during the holding time. An 8-bit 10MS/s analog-to-digital converter is designed using 0.8${\mu}{\textrm}{m}$ CMOS technology. The INL/DNL errors are $\pm$0.5/$\pm$1, respectively. The SNR is 41㏈ at a sampling rate of 10MHz with 100KHz sine input signal. The Power consumption is 4.14㎽ at 10MS/s.

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A Low-power DIF Radix-4 FFT Processor for OFDM Systems Using CORDIC Algorithm (CORDIC을 이용한 OFDM용 저전력 DIF Radix-4 FFT 프로세서)

  • Jang, Young-Beom;Choi, Dong-Kyu;Kim, Do-Han
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.45 no.3
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    • pp.103-110
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    • 2008
  • In this paper, an efficient butterfly structure for 8K/2K-Point Radix-4 FFT algorithm using CORDIC(coordinate rotation digital computer) is proposed. It is shown that CORDIC can be efficiently used in twiddle factor calculation of the Radix-4 FFT algorithm. The Verilog-HDL coding results for the proposed CORDIC butterfly structure show 36.9% cell area reduction comparison with those of the conventional multiplier butterfly structure. Furthermore, the 8K/2K-point Radix-4 pipeline structure using the proposed butterfly and delay commutators is compared with other conventional structures. Implementation coding results show 11.6% cell area reduction. Due to its efficient processing scheme, the proposed FFT structure can be widely used in large size of FFT like OFDM Modem.