• ETRI Journal
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• v.44 no.6
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• pp.925-935
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• 2022

In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.9
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• pp.4549-4566
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• 2017

This work presents a novel facial descriptor, which is named as multiscale adaptive local directional texture pattern (MALDTP) and employed for expression recognition. We apply an adaptive threshold value to encode facial image in different scales, and concatenate a series of histograms based on the MALDTP to generate facial descriptor in term of Gabor filters. In addition, some dedicated experiments were conducted to evaluate the performance of the MALDTP method in a person-independent way. The experimental results demonstrate that our proposed method achieves higher recognition rate than local directional texture pattern (LDTP). Moreover, the MALDTP method has lower computational complexity, fewer storage space and higher classification accuracy than local Gabor binary pattern histogram sequence (LGBPHS) method. In a nutshell, the proposed MALDTP method can not only avoid choosing the threshold by experience but also contain much more structural and contrast information of facial image than LDTP.

• ETRI Journal
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• v.43 no.3
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• pp.377-388
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• 2021

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2008.11a
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• pp.7-10
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• 2008

본 논문에서는 국내에서 DTV 전환에 대비한 기술적 보호조치 방안 마련을 위하여 기술적 보호조치의 방법들에 대하여 간략히 살펴보고 이를 바탕으로 유통활성화를 도모하기 위한 기술적 보호조치 방법을 제안하였다. 디지털 방송프로그램을 보호하기 위한 기술적 보호조치는 인터넷을 통한 불법유통을 방지하여 저작권자의 이익을 도모하려는 목적이나, 이로 인하여 방송프로그램 유통의 지나친 억제는 저작권자의 권익보호를 위하여 바람직하지 않다. 따라서 사용자가 보다 편리하고 저렴한 비용으로 방송프로그램을 재시청 및 재활용할 수 있도록 방송프로그램의 기술적 보호조치를 마련하는 것이 저작권자의 권익을 극대화 할 수 있다. 이러한 방법의 하나로 방송프로그램에 콘텐츠 보호선호 및 콘텐츠의 이용을 위한 연결정보를 포함하여 송출하고 방송수선단말에서 사적이용범위 내에서는 방송프로그램을 자유롭게 녹화 및 복사하여 시청할 수 있지만, 사적이용범위 밖으로 복사/전송 시에는 콘텐츠 연결정보만을 복사하고, 이를 재생할 때는 콘텐츠 연결정보를 이용하여 방송프로그램 유통서버로 연결하며, 유통서버와의 통신을 통하여 저렴하고 편리하게 방송프로그램을 사용할 수 있는 기술적 보호조치의 한 방법을 제안하였다.

• Proceedings of the Korea Contents Association Conference
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• 2014.06a
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• pp.443-444
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• 2014

• The Magazine of the IEIE
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• v.20 no.10
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• pp.23-37
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• 1993

• The Bulletin of The Korean Astronomical Society
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• v.24 no.2
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• pp.83-83
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• 1999

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.90.1-90
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• 1998

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.6
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• pp.2450-2469
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• 2018

In this paper, we develop a spatiotemporal model to analysis of cellular user in underlay D2D communication by using stochastic geometry and queuing theory. Firstly, by exploring stochastic geometry to model the user locations, we derive the probability that the SINR of cellular user in a predefined interval, which constrains the corresponding transmission rate of cellular user. Secondly, in contrast to the previous studies with full traffic models, we employ queueing theory to evaluate the performance parameters of dynamic traffic model and formulate the cellular user transmission mechanism as a M/G/1 queuing model. In the derivation, Embedded Markov chain is introduced to depict the stationary distribution of cellular user queue status. Thirdly, the expressions of performance metrics in terms of mean queue length, mean throughput, mean delay and mean dropping probability are obtained, respectively. Simulation results show the validity and rationality of the theoretical analysis under different channel conditions.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.63-66
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• 1999

We fabricated ramp-edge Josephson junctions with barriers formed by interface treatments instead of epitaxially grown barrier layers. Low-dielectric Sr$_2AITaO_6$(SAT) layer was used as an ion-milling mask as well as an insulating layer for the ramp-edge junctions. An ion-milled YBa$_2Cu_3O_{7-x}$ (YBCO)-edge surface was not exposed to solvent through all fabrication procedures. The barriers were produced by structural modification at the bottom YBCO edge using plasma treatment prior to deposition of the top YBCO electrode. We investigated the effects of pre-annealing and post-annealing on the characteristics of the interface-treated Josephson junctions. The junction parameters were improved by using in-situ RF plasma cleaning treatment.