• Title/Summary/Keyword: Code acquisition

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Improvement of code acquisition time in DS/SS systems using a hybrid scheme (복합방식을 이용한 직접대역확산통신시스템의 코드획득 성능개선)

  • 조권도;김선영
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.3
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    • pp.684-691
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    • 1996
  • Since the period of a spreading code in DS/SS communication systems is generally long, it is necessary to make the code acquisition as fast as possible. The code acquisition time can be sued as a measure to evaluate the performance of code acquisition systems. The search rate of serial search codee acquisition system used in the coventional CDMA cellular system is lower than that of the matched filter technique. In order to reduce the code acquisition time, this paper proposes hybrid code acquisition system composed filters combined with serial search blocks. In the proposed system, the matched filter sweeps possible code phases fast and the acquired phase information is verified by the serial search block. The mean and the variance of its acquisition time are calculated and compared with those of double dwell serial search system. The results indicate better performance of the proposed system by yielding its small vaues of the mean and the variance of code acquisition time.

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A ASIC design of the Improved PN Code Acquisition System for DS/CDMA (DS-CDMA용 개선된 PN 코드 포착 시스템의 ASIC 설계)

  • Jo, Byeong-Rok;Park, Jong-U
    • The KIPS Transactions:PartD
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    • v.9D no.1
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    • pp.161-166
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    • 2002
  • The existing method in PN code acquisition process have a problem in PN code acquisition time because PN code searching is accomplished in one epoch. In this paper, we propose algorithm that can reduce PN code acquisition time because PN code searching is accomplished in each other two epoches. The designed ASIC chip using proposed algorithm confirmed that the area (the number of gates) increase more than existing method in PN code acquisition, but the performance of PN code acquisition is better than existing method.

Design and implementation of the PN code searcher for CDMA mobile station (CDMA 이동국용 PN 부호 탐색기 설계 및 구현)

  • 연광일;곽기달
    • Journal of the Korean Institute of Telematics and Electronics S
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    • v.34S no.8
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    • pp.37-44
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    • 1997
  • We implemented a code searcher which is used for the PN(pseudo noise) code acquisition in CDMA cellular mobile station. To reduce the reuired hardware and the code acquisition time, we used the double dwell structure which is an effective serial code acquisition metho. We designed a code acquisition has acquired within 1/2 PN chip range. The code searcher is implemented using 0.8 micron code searcher is successfully working in CDMA cellular mobile station and it satisfies the code acquisition time specified in IS-95 standard.

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An Efficient Code Acquisition Scheme for DSSS-based Real-Time Locating Systems

  • Lim, Jong-Tae;Park, Hyung-Rae
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.1A
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    • pp.41-48
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    • 2011
  • This paper proposes an efficient code acquisition scheme for direct-sequence spread spectrum (DSSS) based real-time locating systems (RTLS). The proposed scheme employs multiple bit integration to significantly decrease false alarms when no packet signal is transmitted and increase the detection probability when the RTLS tags are excited. The performance of the proposed code acquisition scheme is analyzed and numerically evaluated, and compared with those of single-dwell and traditional double-dwell code acquisition schemes. The simulation results show that the proposed multiple-bit integration scheme outperforms single-dwell and double-dwell schemes.

A FPGA Design of Improved Acquisition System for DS-CDMA (DS-CDMA을 이용한 개선된 동기 획득 시스템의 FPGA 설계)

  • 박종우;조병록;송재철
    • Proceedings of the IEEK Conference
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    • pp.67-70
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    • 1999
  • DS-CDMA is used to widely spread spectrum for a cellular mobile digital communication that maximizing users- capacity at the limited frequency bandwidth, solving technical matters with the channel. Especially, the capability of a spread spectrum receiver relied on fast code acquisition time at the demodulation. In this paper, we considered that fast code acquisition time when a spread spectrum system is designed, and existed code acquisition system set up one code epoch on a position at initial processing, but the proposed code acquisition system improved that two code epoch are set up at the same time, therefore code acquisition time is diminished in effect. The structure modeling to VHDL language. Its synthesized the synthesized and, is implemented FPGA chip

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On the Optimum Dwell Time for Fast Code Acquisition is DS/SS Systems (DS/SS 시스템에서 최소 코드획득시간을 위한 최적 코드측정시간에 관한 연구)

  • 조권도;부수일;김철성
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.30A no.8
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    • pp.11-18
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    • 1993
  • In a spread spectrum system, the bandwidth and period of spreading code is wide and long, respectively. So it is necessary to make the code acquisition time as short as possible. In particular, serial search code acquisition system requires optimum dwell time for fast acquisition. In this paper, code acquisition time is calculated by varying dwell time. Among them, minimum code acquisition time is chosen and then optimum dwell time can be obtained. Detection probability (P$_{D}$) and false alarm probability (P$_{FA}$) can be obtained by integrating chi-square pdf by numerical analysis. The results are compared with that of gaussian approximation method and then it is concluded gaussian approximation method is not suitable for obtaining optimum dwell time. Computer simulation supports theoretical results.

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DS-SS/TDMA Preamble Structure and Code Acquisition Method for Enhanced Code Acquisition Performance (부호획득 성능이 향상된 DS-SS/TDMA 프리앰블 구조 및 부호획득방법)

  • Ryu, Young-Jae;Jang, Jeen-Sang
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.11B
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    • pp.1725-1731
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    • 2010
  • In this paper, we proposed preamble structure and code acquisition method to improve code acquisition performance for DS-SS/TDMA packet communication systems. Proposed algorithm changes the short PN code position depending on the sub slot number. Proposed algorithm also saves position differences between short PN codes and position offsets between short PN codes and data starting position of the TDMA packet. By using the position difference table, proposed algorithm can find out exact data starting position even though some sub slots were defected. As a result of simulation, we concluded that proposed algorithm has at least 5dB gain compared to conventional method when same short PN code is used. Moreover, proposed algorithm shows same code acquisition performance only with 1/4 shortened short PN code compared to conventional method.

Decision Statistics for Noncoherent Serial PN Code Acquisition In Chip-Asynchronous DS/SS Systems (칩비동기 직접수열 대역확산 시스템에서 비동기 직렬 의사잡음코드 포착을 위한 결정통계량)

  • 윤석호;김선용
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.41 no.5
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    • pp.19-25
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    • 2004
  • In this paper, we propose optimal and suboptimal serial code acquisition schemes for chip-asynchronous direct-sequence spread-spectrum systems. The conventional serial code acquisition scheme is to compare each value of correlator outputs with a threshold individually. However, such a scheme is optimum only under the chip-synchronous assumption which is actually very difficult to be held prior to acquisition at the receiver because the signal-to-noise ratios before despreading are very low. In this paper, an optimal serial code acquisition scheme is derived based on the maximum-likelihood criterion under the more realistic and general chip-asynchronous environments. A suboptimal scheme, which is simpler but yields comparable performance to the optimal one, is also derived based on the criterion of local detection power Numerical results show that, under the chip-asynchronous environments, both the optimal and suboptimal serial code acquisition schemes outperform the conventional serial code acquisition scheme.

PN Code Acquisition Technique using A Pre-Dump Correlation Energy in DS-SS Systems (직접대역확산 시스템에서 프리덤프 상관 에너지를 사용하는 PN코드 획득 기술)

  • Yeom, Soo-Nam;Lee, Seong-Joo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.6
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    • pp.22-27
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    • 2011
  • This paper presents an efficient technique to reduce PN code acquisition time considerably by adjusting threshold values in direct sequence spread spectrum (DS-SS) systems. The proposed algorithm employs a pre-dump mode prior to a search mode, and the pre-dump mode determines threshold values of both search and verification modes depending on its correlation energy, which can improve not only the rejection performance of false code phases in the search mode but also that in the verification mode. The proposed method can reduce the mean code acquisition time by about 40% without increase of hardware costs compared with the conventional technique.

Hybrid PN Code Search with Soft-decision Technique (연판정 하이브리드 PN 코드 동기 획득 기법)

  • Lee Seong-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.7A
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    • pp.682-688
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    • 2006
  • In this paper, a soft-decision method for initial PN code acquisition in pilot-channel aided Direct Sequence Code Division Multiple Access (DS-CDMA) systems is proposed in order to improve the acquisition performance. We apply this technique to the conventional hybrid search algorithm and analyze it in terms of mean code acquisition time. For the analysis, we present mathematical model of proposed algorithm and also perform the simulation under IMT-2000 channel models. Numerical results show that our proposed scheme outperforms the conventional one by 0.2 - 0.4 sec with respect to the mean code acquisition time because the soft decision technique can mitigate the possible decline in search performance caused by the use of a hard-decision technique.