• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.55-62
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• 2019

본 논문에서는 K 사용자 MIMO 간섭 채널을 고려하였으며, 정보와 전력을 동시에 전송하는 SWIPT 시스템을 위한 송수신기 설계 방법에 대해서 다룬다. 그리고, 정보 수신 장치와 전력 수확 장치가 같은 수신기에 존재하는 SWIPT 시스템을 고려한다. 제안하는 방식에서는 신호대 누수 잡음비 (SLNR)를 비용 함수로 사용하고, 수확 전력에 대한 임계값을 만족하도록 송수신기를 설계한다. 즉, 수확 전력에 대한 제약 조건 하에서, SLNR을 최대화시키도록 송신단 프리코딩 벡터, 수신단 검파기 벡터, 전력 분배 상수를 동시에 설계한다. 컴퓨터 모의실험을 통하여, 제안하는 기법과 기존 기법의 신호 대 간섭 잡음비 (SINR) 성능을 비교하였다. 사용자 수, 송신 안테나 개수, 수신 안테나 개수 간의 특별한 제약 조건을 만족하는 경우, 제안하는 기법은 낮은 SNR에서 기존 기법보다 우수한 SINR 성능을 나타낸다는 것을 보였다. 또한, 특별한 제약 조건을 만족하지 못하는 경우에는, 제안 기법이 모든 SNR 범위에 대해서 기존 기법보다 더 우수한 성능을 나타낸다는 것을 보였다.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.633-643
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• 2005

An unmanned aerial vehicle (UAV) is an aircraft controlled by .emote commands from ground station and/o. pre-programmed onboard autopilot system. A navigation system in the UAV provides a navigation data for a flight control computer(FCC). The FCC requires accurate and reliable position, velocity and attitude information for guidance and control. This paper proposes an ADGPS/INS integrated navigation system for a UAV. The proposed navigation system comprises an attitude determination GPS (ADGPS) receive., a navigation computer unit, and a low-cost commercial MEMS inertial measurement unit(IMU). The navigation algorithm contains a fault detection and isolation (FDI) function fur integrity. In order to evaluate the performance of the proposed navigation system, two flight tests were preformed using a small aircraft. The first flight test was carried out to confirm fundamental operation of the proposed navigation system and to check the effectiveness of the FDI algorithm. In the second flight test, the navigation performance and the benefit of the GPS attitude information were checked in a high dynamic environment. The flight test results show that the proposed ADGPS/INS integrated navigation system gives a reliable performance even when anomalous GPS data is provided and better navigation performance than a conventional GPS/INS integration unit.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1279-1282
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• 2018

This paper reports the deposition of a metal line using a multilayer stack and laser-induced forward transfer (LIFT) using a low cost continuous wave blue laser with a wavelength of 450 nm. The donor structure was composed of a light-to-heat (LTH) layer, a release layer, and a transfer layer in series. Amorphous silicon as the LTH layer absorbs photon energy and converts it to heat. A release layer was melted so that a silver transfer layer would be transferred to the receiver substrate. The transferred silver layer showed reasonable physical and electrical characteristics. A low cost fine linewidth metal layer could be achieved using this modified LIFT technique and blue laser.

• ETRI Journal
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• 제40권2호
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• pp.218-226
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• 2018

Multiuser detection (MUD) and channel estimation techniques in space-division multiple-access aided orthogonal frequency-division multiplexing systems recently has received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean-squared error (MMSE) MUD exhibits poor performance, although it achieves lower computational complexity. With almost the same complexity, an MMSE with successive interference cancellation (SIC) scheme achieves a better bit error rate performance than a linear MMSE multiuser detector. In this paper, hybrid ML-MMSE with SIC adaptive multiuser detection based on the joint channel estimation method is suggested for signal detection. The simulation results show that the proposed method achieves good performance close to the optimal ML performance at low SNR values and a low computational complexity at high SNR values.

• Smart Structures and Systems
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• 제18권5호
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• pp.885-909
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• 2016

Advances in low-cost wireless sensing have made instrumentation of large civil infrastructure systems with dense arrays of wireless sensors possible. A critical issue with regard to effective use of the information harvested from these sensors is synchronized sensing. Although a number of synchronization methods have been developed, most provide only clock synchronization. Synchronized sensing requires not only clock synchronization among wireless nodes, but also synchronization of the data. Existing synchronization protocols are generally limited to networks of modest size in which all sensor nodes are within a limited distance from a central base station. The scale of civil infrastructure is often too large to be covered by a single wireless sensor network. Multiple independent networks have been installed, and post-facto synchronization schemes have been developed and applied with some success. In this paper, we present a new approach to achieving synchronized sensing among multiple networks using the Pulse-Per-Second signals from low-cost GPS receivers. The method is implemented and verified on the Imote2 sensor platform using TinyOS to achieve $50{\mu}s$ synchronization accuracy of the measured data for multiple networks. These results demonstrate that the proposed approach is highly-scalable, realizing precise synchronized sensing that is necessary for effective structural health monitoring.

• 대한공간정보학회지
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• 제23권3호
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• pp.31-39
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• 2015

본 연구는 NTRIP 기반 보정서비스를 활용한 저가 GPS 수신기의 실시간 측량방법별 정적 및 동적 측위 정확도를 제시한 내용이다. 이를 위해 u-blox사의 LEA 6T GPS 수신 자료와 GNSS 상시관측소의 보정 정보를 NTRIP 캐스터를 매개로 RTKNAVI 공개용 GNSS 해석 툴에 실시간 연계하여 6가지 측량방법(Single, SBAS, DGPS, PPP, RTK, TCP/IP_RTK)으로 위치 정확도를 비교하였다. 정적 실험모형의 적용결과, GPS L1 RTK 측량의 위치오차 평균 및 표준편차는 $N=0.002m{\pm}0.001m$, $E=0.004m{\pm}0.001m$, $h=-0.116m{\pm}0.003m$로서 정밀상대측위 좌표에 근접한 성과를 구현할 수 있었다. 특히, 동적 실험모형에서도 도로 주변 장애물의 영향은 있지만, 모호정수가 고정된 구간의 경우, VRS Network RTK 측량 궤적에 근접한 주행궤적을 보였다. 또한, TCP/IP_RTK 측량용 기준국을 구성하고 정적측량의 활용성을 검토하였다.

• Advances in aircraft and spacecraft science
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• 제2권1호
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• pp.95-108
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• 2015

Automatic Dependent Surveillance Broadcast (ADS-B) is quickly being adopted by aviation safety authorities around the world as the standard for aircraft tracking. The technology provides the opportunity for live tracking of aircraft positions within range of an ADS-B receiver stations. Currently these receiver stations are bound by land and local infrastructural constraints. As such there is little to no coverage over oceans and poles, over which many commercial flights routinely travel. A low cost space based ADS-B receiving system is proposed as a constellation of small satellites. The possibility for a link between aircraft and satellite is dependent primarily on proximity. Calculating the likelihood of a link between two moving targets when considering with the non-periodic and non-uniform nature of actual aircraft flight-paths is non-trivial. This analysis of the link likelihood and the performance of the tracking ability of the satellite constellation has been carried out by a direct simulation of satellites and aircraft. Parameters defining the constellation (satellite numbers, orbit size and shape, orbit configuration) were varied between reasonable limits. The recent MH370 disappearance was simulated and potential tracking and coverage was analysed using an example constellation. The trend of more satellites at a higher altitude inclined at 60 degrees was found to be the optimal solution.

• 정보보호학회논문지
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• 제34권3호
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• pp.393-401
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• 2024

최근 사물인터넷(Internet of Things, IoT)이 인간의 안전, 생명, 자산과 직결되는 산업과 일상생활에 널리 활용되고 있다. 그러나 저가, 경량, 저전력 요건을 충족해야 하는 IoT 장치는 배터리 소모 공격과 간섭 때문에 배터리 라이프타임이 심각하게 단축되는 문제가 있다. 이러한 문제를 해결하기 위해 웨이크업 리시버(Wake-up Receiver, WuR)를 위한 802.11ba 표준이 등장했고, 이 기능은 와이파이 기반 IoT의 에너지 소비를 최소화하는데 중요한 역할을 하고 있다. 그러나 WuR 프로토콜은 지연시간과 오버헤드를 단축하기 위해서 보안 메커니즘을 고려하지 않았다. 따라서 본 연구에서는 배터리 소모 공격에 대응하기 위해서 저전력 웨이크업 리시버를 위한 적응형 파워 세이빙 메커니즘(Adaptive Power Saving Mechanism, APSM)을 제안한다. APSM은 공격이 잦은 환경에서 파워 세이빙 시간을 기하급수적으로 증가시킴으로써 비정상적으로 발생하는 파워 소모량을 최소화할 수 있다. 실험 결과에 따르면, APSM은 전체 트래픽 중 공격 비중이 10% 이상일 때 종래의 파워 세이빙 메커니즘(Legacy Power Saving Mechanism, LPSM)보다 13.77% 이상의 에너지 소비 효율을 개선할 수 있었다.

• Journal of Positioning, Navigation, and Timing
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• 제6권4호
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• pp.149-157
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• 2017

In this study, a system that precisely determines the heave of ship hull was designed using time-differenced GNSS carrier phase measurement, and the performance was examined. First, a technique that calculates precise position relative to the original position based on TDCP measurement for point positioning using only one receiver was implemented. Second, to eliminate the long-cycle drift error occurring due to the measurement error that has not been completely removed by time-differencing, an easily implementable high-pass filter was designed, and the optimum coefficient was determined through an experiment. In a static experiment based on the precise heave measurement system implemented using low-cost commercial GNSS receiver and PC, the heave could be measured with a precision of 2 cm standard deviation. In addition, in a dynamic experiment where it moved up and down with an amplitude of 48 cm and a cycle of 20 seconds, precise heave without drift error could be determined. The system proposed in this study can be easily used for many applications, such as the altitude correction of fish detection radar.

• 대한전자공학회논문지TC
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• 제42권6호
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• pp.1-8
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• 2005

본 논문에서는 1.8GHz 고주파 수신기 전단부의 결함 검사를 위한 새로운 저가의 BIST 회로(자체내부검사회로) 및 설계기술을 제안한다. 이 기술은 입력 임피던스 매칭 측정 방법을 이용한다. BIST 블록과 고주파 수신기의 전단부는 0.25m CMOS 기술을 이용하여 단일 칩 위에 설계되었다. 이 기술은 측정이 간단하고 비용이 저렴하며, BIST 회로가 차지하는 면적은 고주파 전단부가 차지하는 전체면적의 약 $10\%$에 불과하다.