• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.10
• /
• pp.1968-1976
• /
• 2007

This paper proposes a hybrid pseudo-noise (PN) code acquisition scheme for Multicarrier Direct Sequence - Code Division Multiple Access (MC DS-CDMA) mobile communication systems on the code acquisition performance for Nakagami-m fading channel. The hybrid acquisition scheme combines parallel search with serial search to cover the whole uncertainty region of the input code phase. It has a much simpler acquisition hardware structure than the total parallel acquisition and can achieve the mean acquisition time (MAT) slightly inferior to that of the total parallel acquisition. The closed-form expressions of the detection and false-alarm probabilities are derived.

• Proceedings of the IEEK Conference
• /
• 1999.11a
• /
• pp.13-16
• /
• 1999

Many of the currently used PN code acquisition algorithms detect the phase of the incoming PN signal on the basis of ML estimation principle and utilize statistics grounded in taking inner products. As an extension of PN code acquisition algorithm using one auxiliary code introduced by Salih in 1996, we propose a more and optimal (hardware / time / space complexity wise) algorithm by using a vector space approach. We outline some important differences between our algorithm and that introduced by Salih and in the process point out some advantages of our algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.6
• /
• pp.1510-1521
• /
• 1996

This paper presents acquisition algorithm and an improved detection technique for the DS/CDMA (direction sequence code division multiple access) RAKE receiver in multipath fading channel. The DS/CDMA systems use the RAKE receiver, an accurate code acquisition is required for the RAKE branches. The algorithmis able to findthe pseudonoise (PN) code delay estimates for the RAKE branches in a multipath fading channel. In this paper a numerical method and computer simulation simulation have been developed for the acquisition system. The detection probability and mean acquisition time are investigated asa performance measure of the system using the Monte Carlo method. And also in order to analyze the effect of the acquisition on the RAKE receiver this paper bring out the effect of integration time, doppler frequency, processing gain and the number of users on the acquired code phase.

• Journal of the Korea Society of Computer and Information
• /
• v.7 no.3
• /
• pp.128-134
• /
• 2002

In this paper, the performance on the PN code acquisition of DS/CDMA system was analyzed using the Nakagami-m probability density function considered fading environment. The equations on detection probability, $P_D$ and false alarm probability, $P_{FA}$, decision variables affecting the PN code acquisition time were derived and proved using simulation in order to analyze the performance. In conclusion, It was necessary increasing the gain of PLL for correcting phase errors and improving the acquisition performance of PN code in apply to the rake receiver.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3C
• /
• pp.83-91
• /
• 2005

We analyze the performance of an adaptive hybrid search code acquisition algorithm for direct-sequence code division multiple access (DS-CDMA) systems under slowly-moving mobile environments. The code acquisition algorithm is designed to provide the desired feature of constant false alarm rate (CFAR) to cope with nonstationarity of the interference in CDMA forward links. An analytical expression for the mean acquisition time is first derived and the probabilities of detection, miss, and false alarm are then obtained for frequency-selective Rayleigh fading environments. The fading envelope of a received signal is assumed to be constant over the duration of post-detection integration (PDI), considering slow fading environments. Finally, the performance of the designed code acquisition algorithm shall be evaluated numerically to examine the effect of some design parameters such as the sub-window size, size of the PDI, decision threshold, and so on, considering cdma2000 environments.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.6
• /
• pp.22-27
• /
• 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.

• Journal of Satellite, Information and Communications
• /
• v.12 no.1
• /
• pp.120-124
• /
• 2017

In this paper, effect of antenna diversity on pseudorandom noise (PN) code acquisition performance is analyzed and simulated for a direct sequence/code division multiple access (DS/CDMA) overlay system where a CDMA user and a narrowband user coexist in the same frequency band. From the simulation results, it is shown that the antenna diversity is very effective in improving the PN acquisition performance. The results of this paper can be applied to design of synchronization scheme for a DS/CDMA overlay environment.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.28A no.11
• /
• pp.855-865
• /
• 1991

A simple method for analysis of serial search burst-format direct-sequence spread-spectrum (DS-SS) code acquisition system had been recently proposed, and therein, the effect of the code autocorrelation sidelobes on the performance of DS-SS code acquisition system has been assessed [4],[5]. In this paper, a new hybrid scheme which combines the serial search with maximum likelihood search is proposed to eliminate the deleterious effect of code autocorrelation sidelobes, and the performance is analyzed for the additive withe Gaussian noise (AWGN) channels. To analyze the performance of this system, we have generalized the method used in [4],[5] to arbitrary burst-format DS-SS acquisition schemes. The results show that a new hybrid scheme has good immunity against the effect of code autocorrelation sidelobes. Thevalidity of the presented approach has been confirmed form the results of simulation.

• Journal of Satellite, Information and Communications
• /
• v.2 no.1
• /
• pp.1-6
• /
• 2007

In this paper, we proposed new algorithm that improves the acquisition performance of the PN code searcher used in DS-CDMA systems. Using the mean deviation computed from the correlator output of the PN code searcher, it is possible to estimate received channel environment. To satisfy the required acquisition performance in estimated channel environment, the PN code searcher changes the correlator tap size adaptively. Proposed algorithm shows improved performance compared with conventional algorithm using the fixed correlator tap size.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.17 no.4
• /
• pp.17-24
• /
• 2009

According to the GPS modernization, L5 is the third civilian GPS signal, broadcasts in a radio band reserved exclusively for aviation safety services. However, as the code length of GPS L5 is ten times longer than that of GPS L1, the acquisition processing time in GPS L5 takes longer than that of L1. This characteristics make the code phase detected initially change and cause the tracking loop to unlock. In order to overcome this problem, this paper proposes L5 acquisition schemes for the rapid code phase re-search and the fine doppler determination. The feasibility of the proposed scheme is demonstrated through the simulation results.