• Title/Summary/Keyword: spread spectrum communications

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Analysis of Frequency Hopping Signals using Wavelet Transform-Based Scalogram (Wavelet 변환기저 Scalogram을 이용한 주파수 도약신호 분석)

  • 박재오;이정재
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • 2000.08a
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    • pp.45-48
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    • 2000
  • In this paper algorithms of frequency hopping sequences generation such as Lempel-Greenberger, optimum Lempel-Greenberger and Kumar sequences for spread spectrum communications are described. Using the scalogram based on wavelet transform, time-frequency characteristics of frequency hopped signals corresponding to the considered hopping sequences are analyzed.

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SAW MSK Matched Filler for Spread Spectrum Communications (스펙트럼 확산 통신용 SAW MSK 정합필터)

  • Park, E.C.;Park, Y.S.;Whang, K.C.
    • Proceedings of the KIEE Conference
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    • 1987.07b
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    • pp.837-840
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    • 1987
  • In this paper, an MSK modulator and MSK matched Filter using SAW component which is small size and can process high Frequency and wide band signals are described. This modulator and matched Filter have been shown applicable to the transmitter and receiver of spread spectrum communication systems.

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Frequency Compatibility of FH Spread spectrum Communications in TV Channels (FH대역확산통신과 TV채널의 주파수 양립성에 관한 연구)

  • 박창일;조형래;이명수;강창언
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.14 no.1
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    • pp.84-92
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    • 1989
  • The purpose of this paper is to demonstrate the effect of a FH spread spectrum communication interference in TV channels and frequency compatibility in 30-88 MHz frequency band. To calculate this interferece, the strength of electric field of TV signals is derived as a function of distance between TV transmitter and receiver. An interference model is established based upon thefield strength by using the relation between the transmitted power of FH spread spectrum communications and the distance between the TV image signals, which makes TV screen a cceptble, Simultaneous transmission of FH sprea spectrum signals and TV signals is shown to be feasible, as far as the interference level is lower than the TV image signal level by 23.5dBm. As a result of frequency analysis and experiment, the FH spread spectrum communication can be used together with TV channels.

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A study on the optimum wavelet filters and spreading sequences for DWT MC-CDMA (DWT MC-CDMA 시스템을 위한 최적의 웨이브렛 필터 및 확산 순열에 관한 연구)

  • Shin, Jonghong;Jee, InnHo
    • Proceedings of the IEEK Conference
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    • 2001.09a
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    • pp.971-974
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    • 2001
  • Multi-Carrier Spread Spectrum communications has shown the ability of transform domain excision using the wavelet transformation to improve system performance when transmitting signals in the presence of additive white Gaussian noise and interference. In such work, the transforms were implemented using FIR filters and IIR filter. Some well-known classes of sequences, such as Pseudo noise, Walsh, Cold sequences are evaluated with respect to the basic criteria. The main objective is to implement the wavelet transform using IIR filters. This filters are well known to have sharper transition regions leading to better performance. Numerical simulation of multi-carrier spread spectrum communication systems have shown that IIR filters are better in removing the sinusoidal jammer and subsequently yield better BER performance.

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Phase Offset Enumeration Method with Error Detection and Its Application to Synchronization of PN Sequences

  • Song Young-Joan
    • Journal of electromagnetic engineering and science
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    • v.5 no.1
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    • pp.26-30
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    • 2005
  • It is important to know phase offsets of PN(Pseudo Noise) sequences in spread spectrum communications since the acquisition is equivalent to making a phase offset between a receiving PN sequence and a PN sequence of local PN generator be identical. In this paper, a phase offset enumeration method for PN sequences with error detection, and its application to the synchronization are proposed. The phase offset enumeration for an n-tuple PN sequence and its error detection are performed when one period of the sequence is received. Once the phase offset of the receiving sequence is calculated, we can easily accomplish the synchronization by initializing shift registers of a local PN generator according to the phase offset value. The mean acquisition time performance of the proposed scheme was derived analytically. Since this synchronization scheme can be realized by using simple circuit and acquires very rapid acquisition in high SNR but shows performance degradation in low SNR, it can be especially useful in indoor and office environments.

A Study on Co-Channel Interference of FH Spread Spectrum Communications (대역확산통신에서 FH무전기의 상호간섭연구)

  • Choe Eun-Jae;Kim Je-Yeong;Yun Byeong-Chang;Bae Hyeon-Ung;Lee Si-Chang
    • Journal of the military operations research society of Korea
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    • v.16 no.2
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    • pp.118-134
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    • 1990
  • This paper considers the mutual interference problem of several users employing the same FH systems in selected multiple user environments. The environment consists of a desired transmitter-receiver pair located in an area where there are M interfering users distributed in accordance with a specified probability density function. Both coherent Phase-Shift-Keyed and incoherent Frequencey-Shift-Keyed modulations are considered. The general formulas of the average bit error probability are derived. The calculation results are summarized and analyzed. The average bit error probability is highly dependent on the relative location of interferences to the desired link, the time duty factor of the hopping and the number of available channels.

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Approximate Expression of Bit Error Rate in Uplink MC-CDMA Systems with Equal Gain Combining

  • Develi, Ibrahim;Akdagli, Ali
    • Journal of Communications and Networks
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    • v.15 no.1
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    • pp.25-30
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    • 2013
  • Uplink multicarrier code-division multiple-access (MC-CDMA) with equal gain combining (EGC) over Nakagami fading channels is considered. An improved expression which is a feasible alternative for the bit error rate (BER) performance evaluation of MC-CDMA signals is proposed. Simulated annealing algorithm is employed to obtain the optimum value of the coefficients belonging to the proposed expression. Numerical examples show that the performance curves computed by the improved expression are in good agreement with the results obtained by the exact expression. Thus, the proposed expression can improve the accuracy of BER performance evaluation that has been realized by the approximate expression.

A Study on the Improvement of channel efficiency for FH-SS Tranceiver by applying the Frequency synthesizer with high speed switching time. (고속 주파수 합성기를 이용한 FH-SS 송수신기의 채널 효율 개선 연구)

  • 김재향;김기래
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2001.05a
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    • pp.197-200
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    • 2001
  • Recently, Switching time is the principal factor in a design of frerquency synthesizer for Spread-Spectrum Communications. fast switching frequency synthesizer is important to improve the channel efficiency in a Frequency Hopping Spread Spectrum (FH-SS) tranceiver. In this paper, we design the frequency synthesizer with fast switching time as fast as 1${\mu}\textrm{s}$. In frequency synthesizer design, we use the interpolated PLL method inserted memory Look-up table of DDS to reduce switching time, and have result of improved channel efficiency about 20% by applying to FH-SS Transceiver.

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A DPSK Demodulator of Direct Sequence Spread Spectrum using SAW Convolver (탄성표면파 콘벌버를 이용한 직접 시퀀스 대역 확산 통신에서의 DPSK 복조에 관한 연구)

  • Lee, Dong-Wook;Cho, Kwan;Whang, Keum-Chan
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.15 no.6
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    • pp.494-505
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    • 1990
  • This paper reports on the development of a DPSK demodulator of DS spread spectrum communications that use one SAW convolver. The spreading code chip pattern is changed from bit to bit in data portion of packet. And code chip is PSK modulated. Compared with simulation, experiment shows that the DPSK signal spreaded can be demodulated by using only one SAW convolver. And the theoretical performance of this DPSK demudulator is equal to CSK demodulator wich uses two SAW convolvers.

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Interference Rejection using the Data-Recycling Algorithm in DS Spread-Spectrum Communications

  • Kim, Nam-Yong
    • Journal of Electrical Engineering and information Science
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    • v.3 no.1
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    • pp.126-130
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    • 1998
  • In this paper, a new interference rejection filter using the data-recycling technique is presented. The reference signal of the interference rejection filter is formed by using chip decisions, which is correlated with the narrowband interference components of the received signal. The decision feedback techniques reduce the distortion of the desired signal, which is introduced by the interference rejection filter through he use of feedback chip decisions. In order to update the filter coefficients a simple and efficient data-recycling technique that has improved performance over the conventional LMS algorithm is used. The performance of the proposed interference rejection filter is compared to filter with conventional LMS linear filter. The results show that the convergence speed of the proposed interference rejection filter using decision feedback and data-recycling technique is significantly faster than that of the conventional filters. Also, BER performance of the interference rejection filter demonstrates the superiority of the proposed filter algorithm.

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