• Title/Summary/Keyword: Code Phase

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Multiple-Symbol Differential Detection Scheme of Differentially Encoded MultiPhase Clipped MultiCode CDMA System (차동 부호화된 MultiPhase Clipped MultiCode CDMA 시스템의 수신 성능 개선을 위한 다중 심볼 차동 검출 방식 연구)

  • 이병하;안철용;김동구;조진웅
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10A
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    • pp.807-815
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    • 2003
  • MultiCode-CDMA (MC-CDMA) system of chip level MPSK incorporating with clipper (MP-CDMA)[l] shows constant envelope signal which can mitigate the performance degradation due to nonlinear transmit amplifier. In this paper, modulation is modified to carry out differential encoded MPSK rather than MPSK. The modified system is called DMP-CDMA. DMP-CDMA using differential detection has advantages on receiver complexity and pilot overhead. However, it is inferior to coherent detection by about 4.0dB due to inherent power inefficiency of noncoherent detection and the error propagation. Multiple symbol differential detection is employed in order to improve DMP-CDMA using differential detection. As the result, the performance of DMP-CDMA system is improved about 3.6dB compared to differential detection.

Receiver Design for Satellite Navigation Signals using the Tiered Differential Polyphase Code

  • Jo, Gwang Hee;Noh, Jae Hee;Lim, Deok Won;Son, Seok Bo;Hwang, Dong-Hwan;Lee, Sang Jeong
    • Journal of Positioning, Navigation, and Timing
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    • v.10 no.4
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    • pp.307-313
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    • 2021
  • Modernized GNSS signal structures tend to use tiered codes, and all GNSSs use binary codes as secondary codes. However, recently, signals using polyphase codes such as Zadoff-Chu sequence have been proposed, and are expected to be utilized in GNSS. For example, there is Tiered Differential Polyphase Code (TDPC) using polyphase code as secondary code. In TDPC, the phase of secondary code changes every one period of the primary code and a time-variant error is added to the carrier tracking error, so carrier tracking ambiguity exists until the secondary code phase is found. Since the carrier tracking ambiguity cannot be solved using the general GNSS receiver architecture, a new receiver architecture is required. Therefore, in this paper, we describe the carrier tracking ambiguity and its cause in signal tracking, and propose a receiver structure that can solve it. In order to prove the proposed receiver structure, we provide three signal tracking results. The first is the differential decoding result (secondary code sync) using the general GNSS receiver structure and the proposed receiver structure. The second is the IQ diagram before and after multiplying the secondary code demodulation when carrier tracking ambiguity is solved using the proposed receiver structure. The third is the carrier tracking result of the legacy GPS (L1 C/A) signal and the signal using TDPC.

Uncertainty and sensitivity analysis in reactivity-initiated accident fuel modeling: synthesis of organisation for economic co-operation and development (OECD)/nuclear energy agency (NEA) benchmark on reactivity-initiated accident codes phase-II

  • Marchand, Olivier;Zhang, Jinzhao;Cherubini, Marco
    • Nuclear Engineering and Technology
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    • v.50 no.2
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    • pp.280-291
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    • 2018
  • In the framework of OECD/NEA Working Group on Fuel Safety, a RIA fuel-rod-code Benchmark Phase I was organized in 2010-2013. It consisted of four experiments on highly irradiated fuel rodlets tested under different experimental conditions. This benchmark revealed the need to better understand the basic models incorporated in each code for realistic simulation of the complicated integral RIA tests with high burnup fuel rods. A second phase of the benchmark (Phase II) was thus launched early in 2014, which has been organized in two complementary activities: (1) comparison of the results of different simulations on simplified cases in order to provide additional bases for understanding the differences in modelling of the concerned phenomena; (2) assessment of the uncertainty of the results. The present paper provides a summary and conclusions of the second activity of the Benchmark Phase II, which is based on the input uncertainty propagation methodology. The main conclusion is that uncertainties cannot fully explain the difference between the code predictions. Finally, based on the RIA benchmark Phase-I and Phase-II conclusions, some recommendations are made.

CFD Code Development for a Two-phase Flow with an Interfacial Area Transport Equation (계면면적 수송방정식을 적용한 이상유동 해석코드 개발)

  • Bae, B.U.;Yoon, H.Y.;Euh, D.J.;Song, C.H.;Park, G.C.
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2696-2701
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    • 2007
  • For the analysis of a two-phase flow, the interaction between two phases such as the interfacial momentum or heat transfer is proportional to the interfacial area. So the interfacial area concentration (IAC) is one of the most important parameters governing the behavior of each phase. This study focuses on the development of a computational fluid dynamics (CFD) code for investigating a boiling flow with a one-group IAC transport equation. It was based on the two-fluid model and governing equations were calculated by SMAC algorithm. For checking the robustness of the developed code, the experiment of a subcooled boiling in a vertical annulus channel was analyzed to validate the capability of the IAC transport equation. As the results, the developed code was confirmed to have the capability in predicting multi-dimensional phenomena of vapor generation and propagation in a subcooled boiling.

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Phase-Shift-Network-Based Differential Sequential Estimation for Code Acquisition in CDMA Systems (CDMA 시스템에서 부호 획득을 위한 위상 변이 네트워크 기반의 차동 순차 추정 기법)

  • Chong, Da-Hae;Lee, Byeong-Yun;Kim, Sang-Hun;Joung, Young-Bin;Song, Iick-Ho;Yoon, Seok-Ho
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.3A
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    • pp.281-289
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    • 2007
  • In this paper, a novel pseudo noise (PN) code acquisition scheme called the phase-shift-network-based differential sequential estimation (PDSE) is proposed, in the presence of data modulation in code division multiple access (CDMA) systems. The PDSE has even less complexity compared with that of the dual correlating sequential estimation (DCSE), and the reduction in complexity becomes more significant as the period of PN code increases. Numerical results demonstrate that the PDSE performs equivalently to the DCSE with less complexity.

An Investigation of Downcomer Boiling Effects During Reflood Phase Using TRAC-M Code

  • Chon Woo Chong;Lee Jae Hoon;Lee Sang Jong
    • Journal of Mechanical Science and Technology
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    • v.19 no.5
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    • pp.1182-1193
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    • 2005
  • The capability of TRAC-M code to predict downcomer boiling effect during reflood phase in postulated PWR LOCA is evaluated using the results of downcomer effective water head and Cylindrical Core Test Facility (CCTF) experiments, which were performed at JAERI. With a full height downcomer simulator, effective water head experiment was carried out to investigate the applicability of the TRAC-M best estimate LOCA code to evaluate the effective water head with superheated wall temperature in downcomer. In order to clarify the effect of the initial superheat of the downcomer wall on the system and the core cooling behaviors during the reflood phase, two sets of analysis were also performed with a CCTF. Results show that TRAC­M code tends to under-predict downcomer effective water head and core differential pressure. However, the code results show a good agreement with the experimental results in downcomer temperature, heat flux and pressure. Finally, both experiment and calculation showed that the downcomer water head with the superheated downcomer wall is lower than that of the saturated wall temperature.

Adaptive Decision Feedback Equalizer Based on LDPC Code for the Phase Noise Suppression and Performance Improvement (위상잡음 제거와 성능향상을 위한 LDPC 부호 기반의 적응형 판정 궤환 등화기)

  • Kim, Do-Hoon;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.3A
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    • pp.179-187
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    • 2012
  • In this paper, we propose an adaptive DFE (Decision Feedback Equalizer) based on LDPC (Low Density Parity Check) code for phase noise suppression and performance improvement. The proposed equalizer in this paper is applied for wireless repeater system. So as to meet ever increasing requirements on higher wireless access data rate and better quality of service (QoS), the wireless repeater system has been studied. The echo channel and RF impairments such as phase noise produce performance degradation. In order to remove echo channel and phase noise, we suggest a novel adaptive DFE equalizer based on LDPC code. The proposed equalizer helps to compensate RF impairments and improve the performance significantly better than used independently. In addition, proposed equalizer has less iteration number of LDPC code. So, the proposed equalizer system has low complexity.

The Scheme for Improving the Performance of Ranging Code Detection over OFDMA Systems in Uplink (OFDMA 시스템 상향링크의 레인징 부호 검출 성능 향상 기법)

  • Kim Ki-Nam;Kim Jin-Ho;Cho Sung-Joon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.6A
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    • pp.575-585
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    • 2006
  • In Orthogonal Frequency Division Multiple Access (OFDMA) systems, timing synchronization in uplink is accomplished by an initial uplink synchronization called an initial ranging process. The Base Station's receiver synchronizes the symbol timing to specific user's symbol and the other user's symbols have some Symbol Timing Offset (STO). Linear phase shift is occurred by each user's STO in an OFDMA symbol. The Multiple Access Interference (MAI) caused by the summation of each user's linear phase shift degrades the performance of ranging code detection. In this paper, we propose an initial ranging symbol structure with common ranging code for phase shift estimation and compensation. We car estimate the average of phase shift that is generated by each user's STO and compensate this phase shift by using common ranging code. This scheme will suppress the MAI and provide better detection performance than conventional process.

The Low Probability of Intercept RADAR Waveform Based on Random Phase and Code Rate Transition for Doppler Tolerance Improvement (도플러 특성 개선을 위한 랜덤 위상 및 부호율 천이 기반 저피탐 레이다 파형)

  • Lee, Ki-Woong;Lee, Woo-Kyung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.11
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    • pp.999-1011
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    • 2015
  • In modern electronic warfare, RADAR is under constant threat of ECM(Electronic Counter Measures) signals from nearby jammers. The conventional linear frequency modulated(Linear-FM) waveform is easy to be intercepted to estimate its signal parameters due to its periodical phase transition. Recently, APCN(Advanced Pulse Compression Noise) waveform using random amplitude and phase transition was proposed for LPI(Low probability of Intercept). But random phase code signals such as APCN waveform tend to be sensitive to Doppler frequency shift and result in performance degradation during moving target detection. In this paper, random phase and code rate transition based radar waveform(RPCR) is proposed for Doppler tolerance improvement. Time frequency analysis is carried out through ambiguity analysis to validate the improved Doppler tolerance of RPCR waveform. As a means to measure the vulnerability of the proposed RPCR waveform against LPI, WHT(Wigner-Hough Transform) is adopted to analyze and estimate signal parameters for ECCM(Electronic Counter Counter Measures) application.

Phase offset estimation scheme of using STBC with Turbo-code in Fading channel (페이딩 채널에서 STBC와 터보부호 기반의 위상오프셋 추정 기법)

  • Lee, Cheon-Ho;Ryu, Jung-Gon;Heo, Jun
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.1047-1048
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    • 2006
  • In this paper, we present an iterative phase offset estimation algorithm based on a space-time block code and turbo coded system. External single phase estimator receives soft information from the turbo decoder and estimates phase offset with LMS algorithm. The estimated phase offset value is used for space-time decoder. Simulation results show the phase estimation gain in a flat fading channel.

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