• 한국통신학회논문지
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• 제21권3호
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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.

• 전자공학회논문지S
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• 제34S권8호
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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.

• 정보처리학회논문지D
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• 제9D권1호
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• pp.161-166
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• 2002

PN 코드 포착 과정에서 기존의 방식은 한 시점에서 PN 코드를 검색하므로 PN 코드 포착시간에서 문제가 있다. 본 논문에서는 서로 다른 2개의 코드시점에서 PN 코드를 검색하므로 PN 코드 포착시간을 줄일 수 있는 알고리즘을 제안한다. 본 논문에서는 새롭게 제안한 알고리즘으로 ASIC 칩을 설계하였다. 제안한 알고리즘을 이용하여 설계한 ASIC 칩은 기존의 PN 코드 포착과정보다 면적(게이트의 수)은 약간 늘어났지만 PN 코드포착의 성능은 기존의 방법보다 더 좋음을 확인했다.

• Journal of Positioning, Navigation, and Timing
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• 제4권4호
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• pp.151-160
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• 2015

GPS L2C signal is a recently added civil signal to L2 frequency and is constructed by time division multiplexing of civil moderate (L2-CM) and civil long (L2-CL) code signals. While the L2-CM code is 20 ms-periodic and modulates satellite navigation message, the L2-CL code is 1.5s-periodic with 767,250 chips long code sequence and carries no data. Therefore, the L2-CL code signal allows receivers to perform a very long coherent integration. However, due to the length of the L2-CL code, the acquisition of the L2-CL code signal may take too long or require too much hardware resources. In this paper, we propose a three-step ultra-fast L2-CL code acquisition (TSCLA) technique for dual band GPS receivers. In the proposed TSCLA technique, a dual band GPS receiver sequentially acquires the coarse/acquisition (C/A) code signal at L1 frequency, the L2-CM code signal, and the L2-CL code signal to minimize mean acquisition time (MAT). The theoretical performance analysis and numerous Monte Carlo simulations show the significant advantage of the proposed TSCLA technique over conventional techniques introduced in the literature.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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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

• 한국통신학회논문지
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• 제34권6C호
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• pp.649-655
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• 2009

평균 부호 획득 시간은 (mean acquisition time: MAT) 부호 획득 시스템의 성능을 나타내는 가장 중요한 지표이며, MAT가 짧을수록 부호 획득 시스템의 성능이 좋다고 일컬어진다. 광 부호 분할 다중 접속 (optical code division multiple access: O-CDMA) 시스템의 부호 획득을 위해 Keshavarzian과 Salehi가 제안한 multiple-shift (MS) 알고리즘은 부호 획득을 두 단계로 나누어 수행함으로써, 기존 serial-search (SS) 알고리즘에 비해 짧은 MAT를 제공한다. 본 논문에서는 효율적으로 결합된 로컬 신호와 그에 따른 상관값 및 부호를 이용하여 기존 MS 알고리즘에 비해 더 짧은 MAT를 제공할 수 있는 알고리즘을 제안한다. 또한, 모의실험을 통해 제안한 알고리즘이 기존 MS 알고리즘에 비해 더 짧은 MAT를 제공함을 보인다.

• Journal of Positioning, Navigation, and Timing
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• 제13권4호
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• pp.425-430
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• 2024

The public regulated restriction signals are encrypted generally with the very long period code in Global Navigation Satellite System (GNSS) including Global positioning system (GPS). Unlike civilian navigation signals, the long period code is used for the security enhancement purpose. The navigation signals with the long period code are very difficult to acquire due to their own non-periodic characteristics. The application of Acquisition Code (AC) is required for the proper working of the long period navigation signals. In this paper, we present the design and analysis results of the navigation signal with acquisition code. Specifically, the acquisition performance and Time To First Acquisition (TTFA) are presented analytically. In the process of the navigation signal design, we include AC length, insertion pattern, code rate, and filter effects. Also, the navigation signal receiving process include the effects of Side Band Filter (SBF), doppler frequency and code phase errors. The indicators that used to evaluate navigation signal acquisition performance are the detectability and TTFA.

• 전자공학회논문지A
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• 제30A권8호
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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.

• Journal of Positioning, Navigation, and Timing
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• 제2권1호
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• pp.1-8
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• 2013

A signal system for improving the code acquisition complexity of Global Navigation Satellite System (GNSS) receiver is proposed and the receiving correlator scheme is presented accordingly. The proposed signal system is a hierarchical code type with a duplexing configuration which consists of the Zadoff-Chu (ZC) code having a good auto-correlation characteristic and the Pseudo Random Noise (PRN) code for distinguishing satellites. The receiving correlator has the scheme that consists of the primary correlator for the ZC code and the secondary correlator which uses the PRN code for the primary correlation results. The simulation results of code acquisition using the receiving correlator of the proposed signal system show that the proposed signal scheme improves the complexity of GNSS receiver and has the code acquisition performance comparable to the existing GNSS signal system using Coarse/Acquisition (C/A) code.

• 한국통신학회논문지
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• 제35권11B호
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• pp.1725-1731
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• 2010

본 논문은 DS-SS/TDMA 패킷 통신에서 부호획득 성능을 향상시킬 수 있는 프리앰블 구조와 부호획득 방법을 제안한다. 제안된 방법은 프리앰블의 각 구간마다 짧은 확산부호의 위치를 다르게 하교 구간 간의 짧은 확산부호의 위치 차이 및 각 구간의 짧은 확산부호 위치에서 데이터 시작점의 차이를 테이블로 저장함으로써 일부 구간의 수신 오류 시에도 데이터 시작점을 정확하게 판단할 수 있다. 모의실험 결과 제안된 방법은 같은 길이의 짧은 확산부호를 사용할 때 기존 방법에 비해 최소 5dB의 이득이 있으며, 기존보다 1/4 길이의 짧은 확산부호로도 기존방법과 동일한 부호획득 성능을 나타내었다.