• Annual Conference of KIPS
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• 2012.04a
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• pp.1024-1026
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• 2012

본 논문에서는 UWB 기술 기반 WiMedia Distributed Medium Access Control (D-MAC) 프로토콜에서, 디바이스들의 이동성으로 인해 발생하는 Distributed Reservation Protocol (DRP) 예약 충돌 현상을 분석한다. 그리고 DRP 예약 충돌 시 발생하는 성능 저하를 감소시키기 위해 DRP Conflict Resolution 방식과 DRP 릴레이 통신 기술을 제안한다. 본 논문에서 제안하는 DRP 릴레이 통신 프로토콜은 충돌대상 디바이스에게 예약된 자원을 유지할 수 있도록 Direct Link 뿐만 아니라, DRP 예약 충돌 시 릴레이 노드를 경유하여 또 다른 Indirect Link 링크를 빠르게 예약할 수 있는 분산적인 자원 예약 프로토콜을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1554-1557
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• 2020

Looking at the direction of the recent amendments of 802.11 family, there are two major trends. One is to enable the wireless transceivers to support the extremely high-speed wireless transmissions, which has been the mainstream so far. Another big trend is providing a high-performance wireless application platform that meets the demands of the market. This paper summarizes the brand-new IEEE 802.11 amendments from 11ax to 11bf under development by analyzing the innovative features and use cases on them. We provide the vision and direction for the research on the revolutionary data-hungry Wi-Fi 6 and the IEEE 802.11be, alias Wi-Fi 7.

• Annual Conference of KIPS
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• 2010.11a
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• pp.1070-1073
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• 2010

모바일 기기의 통신에 있어 가장 중요한 요소는 이동성 지원이다. 이에 따라 3G 와 같은 이동통신을 지원하는 기술이 출현하게 되었고 이를 통해 이동 중에도 데이터 통신이 가능하게 되었다. 하지만 이동통신은 많은 에너지 소비와 높은 통신 비용문제 등으로 대용량 전송에 적합하지 않은 문제점이 있다. 이에 반해 Wi-Fi 와 같은 Wireless 네트워크는 이동성을 지원하지 않는 대신 허가 받지 않은 주파수 대역을 이용하여(예: Wi-Fi 의 2.4GHz, 5GHz) 높은 대역폭을 제공할 뿐만 아니라 전력을 적게 사용하는 장점이 있다. 본 논문에서는 3G 와 Wi-Fi 을 동시 다중 연결을 통해 서로의 장점을 극대화하고 단점을 보안한 기법을 제시하고 시뮬레이션을 통해 이를 검증 한다.

• Annual Conference of KIPS
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• 2009.11a
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• pp.551-552
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• 2009

조선산업에서 선박의 건조 과정 중 탑재 공정은 작업자 간의 긴밀한 통신을 필요로 하며 매우 위험한 작업이다. 이러한 작업을 음성 품질이 매우 열악한 무전기나 호접속 지연이 많은 주파수 공용통신(TRS)를 이용하여 통신을 하고 있어 매우 위험하다. 따라서, 이러한 기존 통신방식을 대체하는 IP 기반 그룹통신 시스템과 이에 대한 품질 측정 및 평가가 필요하다. 본고에서는 IP 멀티미디어 시스템의 최초의 서비스인 PoC(PTT over Cellular) 서비스를 기반으로 조선산업에서 통합통신(Unified Communication)을 지향하기 위하여, 강재로 인한 매우 열악한 비가시 거리(NLOS)를 극복하고, 효율적인 통신 서비스를 제공하기 위한 엔터프라이즈 PoC을 기반으로 그룹통신의 품질을 측정하고 평가하였다. WiBro 기반 엔터프라이즈 PoC 서비스는 실제적으로 적용이 가능할 뿐 아니라, 실제의 작업자가 통신할때 지연이 느껴지지 않는 1초 이내의 그룹통신 지연시간에 대해 상기 서비스를 분석하였으며, 이론 상으로는 충분히 제공 가능함을 보이고 있다.

• Journal of the Korea Society for Simulation
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• v.25 no.2
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• pp.21-29
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• 2016

Indoor location system has been used Wi-Fi to get a location. After the development of BLE(Bluetooth Low Energy), the interest in the method of a indoor positioning had been move on. It has more advantages than using Wi-Fi. Easy installation, low power consumption, low signal interference and changeable setting(Advertising interval, tx power, etc.). These things can improve efficiency or accuracy in a indoor positioning system. For this reason, recent indoor positioning system uses BLE rather than Wi-Fi. Accordingly, error factors of BLE beacon based indoor positioning should be studying for high accuracy of indoor positioning. In this research, set up few experiment scenarios and keep a close watch on how technological, environmental factor is affecting positioning accuracy. When a application uses largest signal strength to get the indoor location, the mean error of experimental results was decreased compare to using received signal strength in real-time. The result was same when the application applied average and standard deviation to get the indoor location. Changing advertising interval had an effect on the mean error of indoor positioning. Short advertising interval makes the lower mean error than large advertising interval.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.71-80
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• 2007

This paper describes an efficient hardware design of WiBro security processor (WBSec) supporting for the security sub-layer of WiBro wireless internet system. The WBSec processor, which is based on AES (Advanced Encryption Standard) block cipher algorithm, performs data oncryption/decryption, authentication/integrity, and key encryption/decryption for packet data protection of wireless network. It carries out the modes of ECB, CTR, CBC, CCM and key wrap/unwrap with two AES cores working in parallel. In order to achieve an area-efficient implementation, two design techniques are considered; First, round transformation block within AES core is designed using a shared structure for encryption/decryption. Secondly, SubByte/InvSubByte blocks that require the largest hardware in AES core are implemented using field transformation technique. It results that the gate count of WBSec is reduced by about 25% compared with conventional LUT (Look-Up Table)-based design. The WBSec processor designed in Verilog-HDL has about 22,350 gates, and the estimated throughput is about 16-Mbps at key wrap mode and maximum 213-Mbps at CCM mode, thus it can be used for hardware design of WiBro security system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.272-278
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• 2015

This paper analyzed interference impact between wireless headset and Wireless Fidelity which get a high possibility of simultaneously operating in the Industry Science Medical(ISM) bands. Analysis methods of Minimum Coupling Loss(MCL) and Monte Carlo(MC) were applied by using the characters and parameters referenced to Institute of Electrical and Electronic Engineers(IEEE) 802.11b. The protection distance between interferer (WiFi transmitter) and victim (Wireless headset receiver) was calculated through the MCL. The protection distance was obtained for the case of single interferer, and the maximum allowable number of multiple interferers was computed according to the cell radius of a victim system to meet 5 % below of interference probability by using a statistical analysis based on the MC method. The analysis results are expected to be used as a guideline to coexist the wireless headset and low power devices in the ISM band.

• Korean Journal of Radiology
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• v.19 no.6
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• pp.1110-1118
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• 2018

Objective: To perform a meta-analysis to quantitatively assess functional magnetic resonance imaging (MRI) in the diagnosis of locally recurrent prostate cancer. Materials and Methods: A comprehensive search of the PubMed, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews was conducted from January 1, 1995 to December 31, 2016. Diagnostic accuracy was quantitatively pooled for all studies by using hierarchical logistic regression modeling, including bivariate modeling and hierarchical summary receiver operating characteristic (HSROC) curves (AUCs). The Z test was used to determine whether adding functional MRI to T2-weighted imaging (T2WI) results in significantly increased diagnostic sensitivity and specificity. Results: Meta-analysis of 13 studies involving 826 patients who underwent radical prostatectomy showed a pooled sensitivity and specificity of 91%, and the AUC was 0.96. Meta-analysis of 7 studies involving 329 patients who underwent radiotherapy showed a pooled sensitivity of 80% and specificity of 81%, and the AUC was 0.88. Meta-analysis of 11 studies reporting 1669 sextant biopsies from patients who underwent radiotherapy showed a pooled sensitivity of 54% and specificity of 91%, and the AUC was 0.85. Sensitivity after radiotherapy was significantly higher when diffusion-weighted MRI data were combined with T2WI than when only T2WI results were used. This was true when meta-analysis was performed on a per-patient basis (p = 0.027) or per sextant biopsy (p = 0.046). A similar result was found when $^1H$-magnetic resonance spectroscopy ($^1H$-MRS) data were combined with T2WI and sextant biopsy was the unit of analysis (p = 0.036). Conclusion: Functional MRI data may not strengthen the ability of T2WI to detect locally recurrent prostate cancer in patients who have undergone radical prostatectomy. By contrast, diffusion-weight MRI and $^1H$-MRS data may improve the sensitivity of T2WI for patients who have undergone radiotherapy.

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.1
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• pp.256-261
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• 2008

Anorexia is a common symptom in the elderly patients. Causes of anorexia in the elderly are very diverse and multifactorial. Causes include physiological changes associated with aging, mental disorders such as depression, anorexia tardive, dementia, medical diseases such as cancer(lung and gastrointestinal cancer), benign gastrointestinal disorders, cardiac disorders, pulmonary disease, thyroid disorders, infection. Medications such as digoxin, theophylline have also been implicated in the problem. No cause is found in about one quarter of patients. Management is directing at treating causes and providing nutritional support. In Oriental medicine, the appetite has close relation to Biwi. The main cause of anorexia is the insufficiency of Biwi. The physiology of Biwi is that Bi sends clarity(food essence) upward and Wi sends digested food downward. Specially if the physiologic function of Wi is disordered by various factors, Wi cannot send digested food downward. As a result, the anorexia can present by the disorder of Wi function. We experienced a case of an 74 years old female patient with ill-defined severe anorexia differentiated as Wijoongheohan. The patient was managed with fluid therapy and Jeonghyangsiche-tang. The anorexia and other symptoms improved continuously during hospitalization.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.494-497
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• 2004

To date the KOMPSAT OSMI(Ocean Scanning Multi-spectral Imager) data have been widely used in natural disaster monitoring such as Typhoon, Asian Dust, Red Tide, and Forest Fire. Quantitative analyses related to the marine ecosystem have been delayed because they require good quality of data through Cal/Val activities. To resolve such problem, KARI performed the OSMI crosscalibration study with SeaWiFS team. In this study, we will demonstrate the OSMI ocean color products with updated cross-calibration coefficients and compare them to the previous cross-calibration results.