• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.453-459
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• 2009

Due to its capability to resist jamming signals, chirp spread spectrum (CSS) technique has attracted much attention in the field of wireless communications. However, there has been little rigorous analysis for the performance of CSS systems in the presence of jamming signals. In this paper, thus, we present analytic results on the performance of a CSS system: specifically, symbol error rate (SER) expressions are derived for a CSS M-ary phase shift keying (MPSK) system in the presence of broadband and tone jamming signals, respectively. The numerical results show that the empirical SER closely agree with the analytic result.

• The Journal of Information Systems
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• v.27 no.4
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• pp.97-114
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• 2018

Purpose Compliance support system (CSS) aims to support employees' voluntary compliance activities, however, it requires a different approach from the acceptance of other general information systems. In other words, the user's concern that his/her compliance activities recorded in the system are monitored may hinder the active use of the system. In this regard, we set up a research model to investigate the factors that affect the intention to use CSS, by including perceived usefulness, compliance commitment, and surveillance concern. Design/methodology/approach A questionnaire survey was conducted for the employees of a domestic oil-company, who operates their own CSS. Based on the 865 data collected, a structural model analysis using PLS was conducted. As a result, all four hypotheses were accepted. It was found that perceived usefulness of CSS has a positive effect on the intention to use CSS. Compliance commitment has a positive effect both on perceived usefulness and intention to use CSS. In contrast, surveillance concern of one's non-compliance recorded in the CSS was shown to have a negative effect on the relationship between compliance commitment and perceived usefulness. Findings This study has academic implications in that it extends the viewpoint of the existing technology acceptance mechanism by examining the two aspects, i.e., compliance commitment and surveillance concern. This study may also provide practical directions to strengthen the use of the active compliance support system by the employees.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.7
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• pp.1549-1558
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• 2012

Location-aware system is utilized in various fields such as Logistics, Home Network, Healthcare, Military and Transportation systems. In this paper, we designed and implemented a Location-aware system based on IEEE 802.15.4a CSS (Chirp Spread Spectrum) technology in variable environment. The CSS is possible to precision location awareness using RF signal. According to experimental result, the implemented system has recognition error less than 0.5m within 20m radius in space.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.11
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• pp.1124-1131
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• 2014

The chirp spread spectrum (CSS) technique that transmits data signal by using a chirp signal is often used for maritime wireless communication systems such as sound detection radar systems for submarines. However, maritime multipath environment could reduce the data rate of the CSS system. To tackle the problem, an overlap-based CSS transmission scheme is proposed and analyzed in this paper: Based on the approximated Gaussian Q function, we derive a closed form expression of the bit error rate (BER) of the proposed overlap-based CSS system and investigate the mathematical relationship between the number of overlaps and the intersymbol interference (ISI).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.469-475
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• 2009

Overlap is one of the techniques for increasing bit rate in chirp spread spectrum (CSS). More overlaps can offer higher data throughput; however, they may cause more intersymbol interference (ISI) at the same time, resulting in serious bit error rate (BER) performance degradation. Thus, the number of overlaps should be decided according to the required BER performance. In this paper, we derive a closed form expression for BER of the overlap-based CSS system, exploiting the approximated Gaussian Q function. The derived BER expression includes the number of overlaps as a parameter, and thus, would be very useful in determining the number of overlaps for a specified BER. The numerical results demonstrate that the BER derived in a closed form closely agrees with the simulated BER.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.440-446
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• 2010

Convergence of IT and BT is considered in many area, especially in medical care industry. The example of this trend is a capsule endoscope. But in a capsule endoscope, communication through human body has a few restrictions. At first, the transmit power should be limited not to have a bad effect on human organs and for the battery capacity. Second, the channel characteristic of human body has not been examined exactly. Third, general modulation / demodulation techniques which require a channel estimation cannot be used because of battery limit. There also may be a lot of interference signals because a capsule endoscope uses UWB bandwidth. In this paper, we introduce Chirp Spread Spectrum Differential Binary Phase Shift Keying(CSS-DBPSK) and propose Chirp Spread Spectrum On-Off Keying(CSS-OOK) which don't require a channel estimation and robust to interference signals. Using CSS-DBPSK or CSS-OOK, we can get 5 dB or 2~3 dB of Eb/N0 gain at 10-5 target BER. And if there are interference signals, those gains of CSS-DBPSK and CSS-OOK are increased.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.590-592
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• 2008

• Structural Engineering and Mechanics
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• v.50 no.3
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• pp.365-382
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• 2014

In this article, the force method and Charged System Search (CSS) algorithm are used for the analysis and optimal design of truss structures. The CSS algorithm is employed as the optimization tool and the force method is utilized for analysis. In this paper in addition to member's cross sections, redundant forces, geometry and topology variables are considered as the optimization variables. Minimum complementary energy principle is used directly to analyze the structure. In the presented method, redundant forces are calculated by the CSS in order to minimize the energy function. Combination of the CSS and force method leads to an efficient algorithm in comparison to some of the optimization algorithms.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2005.05a
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• pp.274-282
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• 2005

Customer retention is one of the major issued in life insurance industry, in which competition is increasingly fierce. There are many things to do to retain customers. One of those things is to be continuously in touch with all customers. The objective of this study is to design the contact scheduling system(CSS) to support the planers who must touch the customers without having subjective information. Support-planers suffer from lack of information which can be used to intimately touch. CSS that is developed in this study generates contact schedule to touch customers by taking into account existing contact history. CSS has a two stage process. In the first stage, it segments customers according to his or her demographics and contract status data. Then it finds typical pattern and pattern is combined to business rules for each segment. We expert that CSS would support support-planers to make uncontacted customers' experience positive.

• Journal of IKEEE
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• v.17 no.2
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• pp.145-150
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• 2013

In the paper, we propose a new CSS(Complex Signed-Signed) CMA(Constant Modulus Algorithm) algorithm for ICS(Interference Cancellation System). When the repeater get the feedback signal, the CSS CMA algorithm is proposed at the ICS repeater using DSP(Digital Signal Processing) for the removal of interfering signals from the feedback paths. The proposed CSS CMA algorithm improved performances and hardware complexity by adjusting step size values. the steady state MSE(Mean Square Error) performance of the proposed CSS CMA algorithm with step size of 0.00043 is about 4dB better than the conventional CMA algorithm. And the proposed Complex Signed Signed CMA algorithm requires 1950 ~ 2150 less iterations than the LMS(Least Mean Square) and Signed LMS(Normalized Least Mean Square) algorithms at MSE of -25dB.