• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.12
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• pp.1910-1917
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• 1989

This paper shows the performances of asynchronous binary direct-sequence spread-spectrum multiple access communication systems with Rayleigh fading and White Gaussian noise. The performance measures considered are worst-case bit error probability and average SNR depending on code sequences and chip waveforms. The code sequences used are m-sequence and Gold sequence with period 31.The chip waveforms employed are rectangular, sinusoidal and something other chip waveforms.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.276-282
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• 2013

Self-encoded spread spectrum (SESS) is a novel modulation technique that acquires its spreading code from a random information source, rather than using the traditional pseudo-random noise (PN) codes. In this paper, we present our study of the SESS system performance under pulsed-noise jamming and show that iterative detection can significantly improve the bit error rate (BER) performance. The jamming performance of the SESS with correlation detection is verified to be similar to that of the conventional direct sequence spread spectrum (DSSS) system. On the other hand, the time diversity detection of the SESS can completely mitigate the effect of jamming by exploiting the inherent temporal diversity of the SESS system. Furthermore, iterative detection with multiple iterations can not only eliminate the jamming completely but also achieve a gain of approximately 1 dB at $10^{-3}$ BER as compared with the binary phase shift keying (BPSK) system under additive white gaussian noise (AWGN) by effectively combining the correlation and time diversity detections.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.8
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• pp.467-473
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• 2014

In the direct sequence spread spectrum system, the correct synchronization is very important; hence, several acquisition schemes based on the sequential estimation have been developed. Typically, the rapid acquisition sequential estimation (RASE) scheme, the seed accumulating sequential estimation (SASE) scheme, the recursive soft sequential estimation (RSSE) scheme have been developed for the correct acquisition. However, the objective performance comparison and analysis between former estimation schemes have not been performed so far. In this paper, we compare and analyze the performance of the above sequential estimation schemes by simulating the correct chip probability and the mean acquisition time (MAT).

• 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.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.110-117
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• 2003

The result of recent seismic hazard analysis indicates that the ground motion response spectra for Korean nuclear power plant site have relatively large high frequency acceleration contents. In the ordinary seismic fragility analysis of nuclear power plant structures and equipments, the safety margin of design ground response spectrum is directly used as a response spectrum shape factor. The effects of input response spectrum shape on the floor response spectrum were investigated by performing the direct generation of floor response spectrum from the ground response spectrum. The safety margin included in the design ground response spectrum should be considered as a floor response spectrum shape factor for the seismic fragility analysis of the equipments located in a building.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.653-660
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• 2000

In this paper, an adaptive interference excision scheme with multiple adaptive filter bank using an adaptive algorithm is proposed. This scheme suppresses interference in the wavelet packet transform domain for the direct spread spectrum communication systems. Using the Monte-Carlo simulation, we analyze the performance of the direct spread spectrum communication systems with this excision scheme using LMS and RLS adaptive algorithms in AWGN and interference channel.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.258-265
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• 2002

Most structures are expected deform nonlinear and inelastic behavior when subjected to strong ground motion. Nonlinear time history analysis(NTHA) is the most rigorous procedure to compute seismic performance in the various inelastic analysis methods. But nonlinear analysis procedures necessitate more reliable and practical tools for predicting seismic behavior of structures. Some building codes propose the capacity spectrum method. This method is the concept of an equivalent linear system, wherein a linear system having reduced stiffness and increased damping is used to estimate the response of the nonlinear system. This procedure are conceptually simple, but the iterative procedure is time-consuming and may sometimes lead to no solution or multiple solutions. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for mixed building structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.53-60
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• 2002

It has been recognized that damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the inelastic response is required. The methods available to the design engineer today are nonlinear time history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. Some codes proposed the capacity spectrum method based on the nonlinear static(pushover) analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method to evaluate seismic Performance of structure, without iterative computations, given the structural initial elastic period and yield strength from the pushover analysis, especially for multi degree of freedom structures. The purpose of this paper is to investigate accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1015-1023
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• 1999

We propose nonlinear processing schemes for robust acquisition of direct-sequence spread spectrum (DS/SS) signals in wideband pulse jamming. To mitigate the interference effect due to impulse-like wideband jamming signals, the received signal is preprocessed by using the median filter, a simple order statistic filter Since only parts of the PN sequence are used for rapid acquisition, it is indispensable for analytic design of an acquisition scheme to have an appropriate model of the partial PN signal. The partial correlation of the median filtered PN signal is approximated by a two-piecewise linear model using an approximate upper bound. The acquisition performance of the proposed schemes is compared to that of other schemes. Finally, the analytic design is verified by computer simulation.