• Journal of KIISE
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• v.45 no.3
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• pp.303-310
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• 2018

LoRaWAN(Long Range Wide Area Network) is a standard for low-power, long-range, low-speed communication as announced in the LoRa Alliance. LoRaWAN addresses the physical layer and medium access control layer and the technology used in the physical layer is referred to as LoRa. LoRa can be used for remote monitoring and remote control in maritime conditions. However, unlike land, marine environment is not only difficult to construct an infrastructure for service provision, but also difficult to analyze LoRa performance in maritime. In this study, we construct an infrastructure using cloud platform and analyze LoRa link performance in maritime conditions.

• Journal of Korean Society of Transportation
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• v.19 no.6
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• pp.19-31
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• 2001

In this paper, 3 layered architecture model and related design guidelines are proposed, which have been actually applied in our national ITS-Architecture design. The domain architecture as the 1st layer is to structure all ITS related domains for maximizing the co-operability in national level. The logical architecture as the 2nd layer is to structure all ITS related application-systems for minimizing duplications, conflicts and dead-zones in service level and maximizing the co-operability in application-system level. The physical architecture as the 3rd layer is to structure all IT(Information Technology) related physical resources for maximizing.

• Current Optics and Photonics
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• v.5 no.5
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• pp.576-582
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• 2021

Dichroic beam-splitter (DBS) with polarization-maintaining took an important role in the free space quantum telecommunication tests on the Micius satellite of China. In this presentation, we designed and prepared a 50 layer polarization-maintaining DBS coating by a dual ion beam sputtering deposition (Dual-IBS) method. In order to solve a stress problem, an 18 layer special anti-reflection (AR) coating with similar physical thickness ratio was deposited on the backside. By stress compensation, the surface flatness RMS value of the DBS sample decreased from 0.341 λ (@632.8 nm) to 0.103 λ while beam splitting and polarization maintaining properties were almost kept unchanged. Further, we discussed the mechanism of film stress and stress compensation by equation deduction and found that total stress had a strong relationship with the total physical thickness and the ratio of layer materials.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.6
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• pp.458-463
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• 2016

In this paper, the fuzzy structure model for the consciousness structure of social workers related to the elder abuse factors was derived and analyzed. The characteristics of the model was obtained as follows. First, the elder abuse behavior at the top layer was related to the attitude of the elderly and the work overload of social workers. Second, the attitude of the elderly and the work overload of social workers at the middle layer were related to the personality of social worker, the physical and mental dependency of client, and the personality of client. Third, the personality of social worker, the knowledge of the elderly, the personality of client, and the physical and psychological dependence of the client affected directly the elder abuse behavior without going through the middle layer. Fourth, the work overload of social workers at the middle layer was affected the attitude of the elderly. Finally, the age of social workers, the working image, the job training, and provision of punishment to the social workers were the isolated layer, in which the relationship between the elder abuse behavior and related factors was not found.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.10
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• pp.5080-5097
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• 2017

Channel characteristics-based secret key generation is an effective physical-layer security method. The issues of how to remove the effect of random noise and to balance the key generation rate (KGR) and the bit mismatch rate (BMR) are needed to be addressed. In this paper, to reduce the effect of random noise and extract more secret bits, a new quantization scheme with high key generation rate and low bit mismatch rate is proposed. In our proposed scheme, we try to use all measurements and correct the differences caused by noise at the boundary regions instead of simply dropping them. We evaluate and discuss the improvements of our proposed scheme. The results show that our proposed scheme achieves lower bit mismatch rate as well as remaining high key generation rate.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.963-966
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• 2001

The wideband DS-CDMA (W-CDMA) system is one of the candidates for the next generation mobile communication system known as IMT-2000. The important concept of W-CDMA is the introduction of intercell asynchronous operation. In this paper, we design and analyze the system level simulator for the International Mobile Tele communication - 2000 (IMT-2000) 3-rd generation partnership project (3GPP) system. We confirm how the simulator works by BER over different Eb/NO. This study will be expected to use as reference data in the development of asynchronous IMT-2000. In this paper, we analyze a physical layer of W-CDMA system and design a transmitter and receiver by using ADS (Advanced Design System). Also, we simulated a link level performance in Rayleigh fading channel environment. This study will be useful in the analysis and design of W-CDMA system.

• ETRI Journal
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• v.36 no.1
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• pp.183-186
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• 2014

In this letter, we consider a cooperation system with multiple untrusted relays (URs). To keep the transmitted information confidential, we obtain joint channel characteristics (JCCs) through combining the channels from the source to the destination. Then, in the null space of the JCCs, jammers construct artificial noise to confuse URs when the source node broadcasts its data. Through a distributed implementation algorithm, the weight of each node can be obtained from its own channel state information. Simulation results show that high-level security of the system can be achieved when internal and external eavesdroppers coexist.

• ETRI Journal
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• v.36 no.2
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• pp.329-332
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• 2014

In this letter, the problem of estimating the physical layer (PL) scrambling code sequence of DVB-S2 is studied. We present the first ever scheme to estimate the scrambling sequence. The scheme is based on hypothesis testing. By analyzing the PL scrambling process, we construct a new sequence equivalent to the scrambling sequence. We then use hypothesis testing to estimate the new sequence. The threshold for the hypothesis testing is also discussed. The experiment results show that the performance of our estimation scheme can work even under high BER.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.422-436
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• 2020

In this paper, we investigate the impact of antenna correlation on secure transmission in a multi-eavesdropper single-input multiple-output (SIMO) system, where the receiver and eavesdroppers are equipped with correlated antennas. Based on the practical passive eavesdropping system, the new closed-form expressions of secrecy outage probability (SOP) and non-zero secrecy capacity probability are derived to explore the effect of antenna correlation on the system with multiple eavesdroppers. To further analyze the secrecy performance of the investigated system, we theoretically derive the expression of asymptotic SOP to clearly show the diversity order and array gain. Finally, Monte Carlo simulations verify the effectiveness of our theoretical results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1282-1290
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• 1998

In this paper, the physical layer design of IMT-2000 system being developed by SK Telecom is introuduced. The outband signaling scheme and the two-pilot scheme are adopted for multimedia service and inter-cell asynchronous mode respectively. In addition, the synchronous transmission scheme is proposed to reduce the interference in the reverse link. The algorithm and simulation results of 'two-pilot scheme' for inter-cell asynchronous mode and 'reverse synchronous control' for synchronous transmission are presented.