• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8C
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• pp.1025-1033
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• 2004

This paper covers the detection of covert direct sequence spread spectrum signal without the PN(Pseudo Noise) code information. Due to its low probability of interception, the difficulty of spectrum surveillance increases. Detection parameters are the signal existence of given bandwidth, the length of spreading sequence used by transmitter, and the identification of spreading code for detected chip length. The triple correlation function(TCF) value which is one of the higher order statistical signal processing techniques can be used to detect spread spectrum signal without a prior knowledge, but, it has weakness that TCF results depend on the spread data sequence in actual application. This paper proposes the new scheme that not only overcomes the weakness but also presents better performance than the traditional TCF scheme. The performance comparison of conventional TCF with proposed technique shows that the triple correlation estimator(TCE) has better detection capability.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.370-381
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• 2021

This paper presented an efficient transceiver structure of multiband Frequency Shift Keying (FSK) signals with direct sequence spread spectrum for maintaining covertness and performance. In aspect to covertness, direct sequence spread spectrum method, which multiplying by Pseudo Noise (PN) codes whose rate is much higher than that of data sequence, is employed. In aspect to performance, in order to overcome performance degradation caused by multipath and Doppler spreading, we applied multiband, turbo equalization, and weighting algorithm are applied. Based on the simulation results, by applying 4 number of multiband and number of chips are 8 and 32, experiments were conducted in a lake with a distance of moving from 300 m to 500 m between the transceivers. we confirmed that the performance was improved as the number of bands and chips are increased. Furthermore, the performance of multiband was improved when the proposed weighting algorithm was applied.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.304-313
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• 2021

This paper presents the results of a sea trial for long range underwater acoustic communication conducted in the East Sea in November 2020. Signals were collected through a moving transmitter and 16 vertically arranged receivers, and the range between the transmitter and receiver was about 20 km. The signal in the experiment is a conventional Direct Sequence Spread Spectrum (DSSS) method and a superimposed DSSS method that increases data rate by superimposing of multiple circulated Pseudo Noise (PN) sequences for each symbol. The results show that the uncoded bit error rate averaged over 16 channels to which the channel coding technique was not applied was 0.0005 for the conventional direct sequence spreading method, and was 0.00124 for the superimposed direct sequence spreading method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.6
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• pp.475-484
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• 1990

This paper proposes a method for the implementation of a power line communication equipment using power line synchronization in a direct-sequence spread spectrum communication system. In order to implement a network using a power line as a transmission channel we have investigated the utilization of direct-sequence speread spctrum which gives such advantages as robustness against narrow-band interference and noise, and realization of multiple access. In a power line, however, complexity of synchronization makes it difficult to realize a multiple access and cost down and system simplification. The proposed technique of power line synchronization makes it possible to get cost down and system size small, and the realization of multiple communication can be achieved by the addition of address setting circuit.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.7
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• pp.8-15
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• 1995

We have proposed a new fast serial serch algorithm and a receiver for direct-sequence spead-spectrum acquisition systems and analyzed its perfoemance. This algorithm achieves faster acquisition by more than two times that of existing algorithm. We have derived equations of the mean acquistion time by using moment generating function and direct approach, and presented numerical results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.10-15
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• 2009

In this paper, we propose a frequency-domain tone interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms, the interference signal is estimated and compensated in the frequency-domain and then, with IFFT (inverse Fourier transform), the compensated frequency-domain signal is transformed to the time domain signal for the remaining receiver operations. Unlike the previous works, the proposed algorithm does not requires IFFT and thus, the proposed algorithm not only shows the virtually identical performance but also requires lower hardware complexity compared to the previous works.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.105-114
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• 1984

A fast pseudo-noise (PN) sequence acquisition algorithm for the direct-sequence (DS) spread spectrum system is proposed. The basic concept of the algorithm has been adopted from that of the classical sliding correlator. Mathematical modeling, analysis and computer simulation of the proposed system have been done. The results of analysis and computer simulation show that the acquisition system yields a significant performance improvement over the sliding correlator. Its acquisition time takes only 45 ms when signal-to-noise ratio(SNR) is -18dB. The algorithm developed has been implemented in hardware and its experimental result is also given.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1976-1981
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• 2013

In this paper, we propose a frequency-domain interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms that protocol defines the rules concerning the collection of means of Transmission Control Protocol (TCP: Transmission Control Protocol) is the most widely used in the transport layer. Two-way traffic through the network path to the same end-to-end transfer of data in the opposite direction between pairs of nodes are infused with two or more TCP connection using the network traffic patterns from the exchanger and routers share results of approval. Per-flow input/output structure of matter using the LTS online reaction when evaluated as this is the most important factor. TCP-MT when the connection duration is one of the largest performance gains.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.537-546
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• 2001

Griffth's and LCCMA which are Single-user detection adaptive algorithm are proposed for mitigate MAI(multiple access interference) and the near-far problem in direct-sequence spread-spectrum CDMA system and MOE Algorithm is proposed for MMSE(Minimum Mean-Square Error). This paper pertains to three types of Blind adaptive algorithms which can upgrade system functionality without the requirements from training sequence. It goes further to compare and analyze the functionalities of the algorithms as per number of interfering users or data update rate of the users. The simulation results was that LCCMA algorithm was superior to other algorithms in both areas. Blind application enabled a more flexible network design by eliminating the necessity of training sequence.