• Title, Summary, Keyword: code timing estimation

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Improved Code Timing Estimator for DS-CDMA Systems Using Correlated Antennas in Time-Varying Fading Channels (시변 페이딩 채널에서 상관관계가 있는 안테나를 사용하는 DS-CDMA 통신 시스템을 위한 개선된 최대가능도 코드 타이밍 추정기)

  • Kim Sang-Choon;Jeong Bong-Sik
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.5
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    • pp.910-920
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    • 2006
  • We consider the problem of estimating a code-timing of DS-CDMA signal in antenna array systems in the presence of flat fading channels and near-far environments. We derive an approximate maximum likelihood algorithm of estimating the code-timing of a desired user for DS-CDMA systems to better utilize the time-varying characteristics of the fading process. In the development of code timing estimator, the given observation bits are divided into many sets of sub-windows with each sufficiently large. The proposed method uses sub-windows with equal size associated with the coherence time of channel fading. The alternative approach is that without the estimation of the fading rate, the sufficiently given observation bits are simply separated into two consecutive sets of sub-windows. The derivation of the proposed algorithms is based on multiple antennas partially correlated in space. The impacts of spatial fading correlation on acquisition and men acquisition time performance of the proposed algorithms are also examined.

Navigation Signals Based on Orthogonal Tiered Polyphase Code

  • Lee, Jewon;Kim, Jeong-been;Kim, Kap-jin;Song, Ki-won;Ahn, Jae Min
    • Journal of Positioning, Navigation, and Timing
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    • v.4 no.3
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    • pp.97-105
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    • 2015
  • A navigation signal based on orthogonal tiered polyphase code was proposed. For the proposed signal, tiered polyphase code was used as the code of a pilot channel. Tiered polyphase code is a complex number type code, and thus the pilot channel and data channel were separated using the Walsh code which makes the correlation between different codes become 0. The results of the simulation indicated that the correlation characteristics and signal acquisition performance of the proposed signal were identical to those of tiered polyphase code, and that the disadvantage of tiered polyphase code could be supplemented through a data channel in terms of signal tracking.

Performance Comparison of Different GPS L-Band Dual-Frequency Signal Processing Technologies

  • Kim, Hyeong-Pil;Jeong, Jin-Ho;Won, Jong-Hoon
    • Journal of Positioning, Navigation, and Timing
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    • v.7 no.1
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    • pp.1-14
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    • 2018
  • The Global Positioning System (GPS) provides more accurate positioning estimation performance by processing L1 and L2 signals simultaneously through dual frequency signal processing technology at the L-band rather than using only L1 signal. However, if anti-spoofing (AS) mode is run at the GPS, the precision (P) code in L2 signal is encrypted to Y code (or P(Y) code). Thus, dual frequency signal processing can be done only when the effect of P(Y) code is eliminated through the L2 signal processing technology. To do this, a codeless technique or semi-codeless technique that can acquire phase measurement information of L2 signal without information about W code should be employed. In this regard, this paper implements L2 signal processing technology where two typical codeless techniques and four typical semi-codeless techniques of previous studies are applied and compares their performances to discuss the optimal technique selection according to implementation environments and constraints.

Development of a CSGPS/DR Integrated System for High-precision Trajectory Estimation for the Purpose of Vehicle Navigation

  • Yoo, Sang-Hoon;Lim, Jeong-Min;Oh, Jeong-Hun;Kim, Ho-Beom;Lee, Kwang-Eog;Sung, Tae-Kyung
    • Journal of Positioning, Navigation, and Timing
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    • v.4 no.3
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    • pp.123-130
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    • 2015
  • In this study, a carrier smoothed global positioning system / dead reckoning (CSGPS/DR) integrated system for high-precision trajectory estimation for the purpose of vehicle navigation was proposed. Existing code-based GPS has a low position accuracy, and carrier-phase differential global positioning system (CPDGPS) has a long waiting time for high-precision positioning and has a problem of high cost due to the establishment of infrastructure. To resolve this, the continuity of a trajectory was guaranteed by integrating CSGPS and DR. The results of the experiment indicated that the trajectory precision of the code-based GPS showed an error performance of more than 30cm, while that of the CSGPS/DR integrated system showed an error performance of less than 10cm. Based on this, it was found that the trajectory precision of the proposed CSGPS/DR integrated system is superior to that of the code-based GPS.

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.

Design and Performance Analysis of a Decision-feedback Coherent Code Tracking Loop for WCDMA Systems (WCDMA 시스템을 위한 판정궤환 동기식 동기추적 회로의 설계 및 성능분석)

  • 박형래;양연실;김영선;김창주
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.4A
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    • pp.429-438
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    • 2004
  • In this paper, a decision-feedback coherent code tracking loop is designed for WCDMA systems and its performance is analyzed in terms of jitter variance considering the effect of phase and symbol estimation errors for both AWGN and fading environments. An analytical closed-form formula for jitter variance is Int derived for AWGN environments as a function of a pulse-shaping filter, timing offset, signal-to-interference ratio, and loop bandwidth while involving the phase estimation error and bit error rate, and the upper bound of jitter variance is derived for fading environments. Finally a second-order coherent code tracking loop is designed with the DPCH frame format #13 of the WCDHA forward link selected as a target system, and its performance is evaluated by the closed-form formula and compared with the simulation results for both AWGN and Rayleigh fading environments.

Test Results of Wide-Area Differential Global Positioning System with Combined Use of Precise Positioning Service and Standard Positioning Service Receiver

  • Kim, Kap Jin;Ahn, Jae Min
    • Journal of Positioning, Navigation, and Timing
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    • v.10 no.1
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    • pp.43-48
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    • 2021
  • Most existing studies on the wide-area differential global positioning system (WADGPS) used standard positioning service (SPS) receivers in their observation reference stations which provide the central control station global positioning system (GPS) measurements to generate augmentation data. In the present study, it is considered to apply a precise positioning service (PPS) receiver to an observation reference station which is located in the threatened jamming area. Therefore, the reference station network consists of a PPS receiver based observation reference station and SPS receiver based observation reference stations. In this case, to maintain correction performance P1C1 differential code bias (DCB) should be compensated. In this paper, P1C1 DCB estimation algorithm was applied to the PPS/WADGPS system and performance test results using measurements in the Korean Peninsula were presented.

A Pilot-Tone Based Channel Estimation Technique for Cooperative SFBC-OFDM Systems (Cooperative SFBC-OFDM 시스템을 위한 파일럿 톤 기반의 채널 추정 기법)

  • Park, Chang-Hwan;Ko, Yo-Han;Lee, Hee-Soo;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.9C
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    • pp.661-668
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    • 2008
  • In this paper, a channel estimation technique based on pilot tones is proposed for cooperative SFBC-OFDM systems with a STO(Symbol Timing Offset). In a cooperative SFBC-OFDM system, the STO between RS(Relay Station) and MS(Mobile Station) varies depending on the location of MS. Since the STO causes distortion in the form of phase rotation, a channel estimation technique based on linear interpolation with respect to phase and amplitude is proposed for the case of orthogonal pilot allocation. Also, a channel estimation technique is proposed by solving nonlinear equation for the case of pilot structure with orthogonal code. It is shown by computer simulation that the performance of channel estimation can be significantly improved when the proposed techniques are applied to cooperative SFBC-OFDM systems with STO.

Assessment of a Low Power Offset BPSK Component for Spreading Code Authentication

  • Maier, Daniel S.;Pany, Thomas
    • Journal of Positioning, Navigation, and Timing
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    • v.9 no.2
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    • pp.43-50
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    • 2020
  • In this paper a low power Spreading Code Authentication (SCA) sequence with a BPSK(1) modulation at a frequency offset of +7.161 MHz is tested for authentication purposes, the Galileo E1OS is used as base signal. The tested signals comprise a Galileo constellation with 5 satellites including the Galileo OS Navigation Message Authentication (OSNMA) and a low power offset BPSK (OBPSK(7,1)) as SCA component. The signals are generated with the software based MuSNAT-Signal-Generator. The generated signals were transmitted Over-The-Air (OTA) using a Software-Defined-Radio (SDR) as pseudolite. With a real-environment-testbed the performance of the SCA in real channel conditions (fading and multipath) was tested. A new SCA evaluation scheme is proposed and was implemented. Under real channel conditions we derive experimental threshold values for the new SCA evaluation scheme which allow a robust authentication. A Security Code Estimation and Replay (SCER) spoofing attack was mimicked on the real-environment-testbed and analyzed with the SCA evaluation scheme. It was shown that the usage of an OBPSK is feasible as an authentication method and can be used in combination with the OSNMA to improve the authentication robustness against Security SCER attacks.

FPGA Implementation of BCH Encoder to change code rate (부호율 변경이 가능한 BCH Ecoder의 FPGA구현)

  • Jegal, Dong;Byon, Kun-sik
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.485-488
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    • 2009
  • The class of BCH codes is a large class of error correction codes. HDL implementation of BCH code generator to change code rate. and used System Generator, and implemented hardware to FPGA. Loaded bit stream to a FPGA board in order to verify this design to Hardware co-simulation from these results. Also, compared as investigated the maximum action frequency through timing analysis and resource of logic in order to evaluate performance of BCH code generator.

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