• Current Optics and Photonics
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• 제3권3호
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• pp.210-214
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• 2019

The allowable path-deviation time of aircraft in a free-space optical communication system has been estimated from various trajectories, using different values of aircraft speeds and turn rates. We assumed the existence of a link between the aircraft and a ground base station. First, the transmitter beam's divergence angle was calculated through two different approaches, one based on a simple optical-link equation, and the other based on an attenuation coefficient. From the calculations, the discrepancy between the two approaches was negligible when the link distance was approximately 110 km, and was under 5% when the link distance ranged from 80 to 140 km. Subsequently, the allowable path-deviation time of the aircraft within the tracking-error tolerance of the system was estimated, using different aircraft speeds, turn rates, and link distances. The results indicated that the allowable path-deviation time was primarily determined by the aircraft's speed and turn rate. For example, the allowable path-deviation time was estimated to be ~3.5 s for an aircraft speed of 166.68 km/h, a turn rate of $90^{\circ}/min$, and a link distance of 100 km. Furthermore, for a constant aircraft speed and turn rate, the path-deviation time was observed to be almost unchanged when the link distance ranged from 80 to 140 km.

• 대한임베디드공학회논문지
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• 제5권3호
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• pp.152-156
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• 2010

Non-line-of-sight (NLOS) propagation is one of the challenges in radio positioning. Distinguishing the transmission status of the communication as line-of-sight (LOS) or NLOS is of great importance for the wireless communication systems. This paper focuses on the identification of NLOS based on time-of-arrival (TOA) distance estimates and the received signal strength (RSS) measurements. We set a path loss threshold based on the joint TOA and RSS based NLOS detection method to determine LOS or NLOS. Simulation results show that the proposed method ensures the correct of detection for the LOS condition and can improve the NLOS identification for the weak noise and long distance.

• Journal of information and communication convergence engineering
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• 제4권2호
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• pp.62-66
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• 2006

The objective of this thesis is to measure the limit of the real space where wireless Local Area Network (LAN) is used, and to apply this result as reference to set up a real Wireless LAN environment. The organized circumference was composed of Wireless LAN based on IEEE 802.11b of the American standard, and the examination is carried out on the campus. On the real condition of office environment and open space, the ratio of available distance to a signal at each distance was measured and this result was studied as data to embody wireless LAN on the campus. The measurement under an indoor environment was executed under circumstance having two walls and open space, however, was executed respectively under three circumstances: Where no obstacle, where one wall exists, and where two or more walls exist.

• 한국인터넷방송통신학회논문지
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• 제10권3호
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• pp.121-129
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• 2010

본 논문에서는 중계기의 위치에 따른 협력 통신의 성능을 분석한다. 이를 통해 최적의 중계기는 송신단과 수신단의 신호 전송의 성능을 높이거나 송신단의 신호를 수신단이 복호하지 못하였을 경우 재전송을 하는 일종의 송신단 역할을 한다. 본 논문에서는 최적의 중계기를 선택함으로써의 성능 향상을 보이며 관련 수식을 유도한다.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.14-19
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• 2015

Recently, water sewage disposal facilities are able to manage real-time data collection and record management through compact broadband modem LAN switching technology. Therefore, it needs more stable and efficient facility management. So, we required practical use of environmental facilities convergence based on broadband integrated modem. In this paper, we proposed short distance wireless communication network of compact broadband modem for sewage disposal facilities. And it received data inside of water treatment facility using the two communication methods (IEEE802.11x and IEEE802.15.4x). Then, our proposed an data-flow control algorithm of wireless network technology will prioritize processing data when emergency happen through collecting data, analysis data and processing. Lastly, we proved usefulness by experiment and simulation analysis.

• 로봇학회논문지
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• 제16권3호
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• pp.232-237
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• 2021

In this research, a real-time tele-operation system for unmanned excavator using the LTE communication system is suggested. The distance between the operator and the excavator is limitless as long as the LTE communication available. The motion and video data of the excavator is synchronized using the Vehicle Control Unit (VCU) and streamed to the operator for immersion feeling. The video is played on the operator's monitor and the motion data is used to regenerate the excavator movement on the developed master platform. In general, a excavator is tele-operated using RF signal and the maximum distance for direct control is limited to within a hundred meter. In this research, the immersion tele-operation system is suggested for excavator operation within an 100ms time delay using the developed master platform, the VCU and LTE communication. A successful test run of the suggested tele-operation system has already been performed between an operator in Songpa (Seoul) and a excavator in Ansan (Gyeonggi-do) which is approximately 35 km apart.

• 한국인터넷방송통신학회논문지
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• 제9권5호
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• pp.85-91
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• 2009

IT기술의 발전과 함께 유비쿼터스 (Ubiquitous)환경이 도래하여, 무선 센서 네트워크(Wireless Sensor Networks)기반 연구가 다방면에서 활발히 진행 중에 있다. 본 논문에서는 무선 센서 네트워크에서 센서간 거리를 전방위로 측정할 수 있는 간단한 방안에 대해 제안한다. 그리고 이를 직접 설계하고 구현하여 실험을 통해 검증해 본다. 전방향성 장치를 이용하면 거리 측정 최대 거리는 줄어드는 단점이 있지만 $360^{\circ}$ 방향을 측정 할 수 있다는 장점이 있다. 본 논문에서는 실제 환경에서 실험을 통하여 전방향성 장치가 존재할 경우와 그렇지 않은 경우에 대하여 초음파를 통한 거리측정 방식의 누락율 및 정확도를 분석해 본다.

• 한국전자통신학회논문지
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• 제7권4호
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• pp.861-866
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• 2012

현재까지 코일을 이용한 자성물질 가속에 코일과 자성물질간의 최적한 거리를 명시한 적이 없다. 전류세그먼트 코일구조와 그 다단계를 이용하여 자성물질을 가속 시 통상 코일과 자성 물질이 가깝게만 있으면 최적한 것으로 알고 있으나 미분법으로 극대점을 찾은 결과 코일간의 거리에 대한 절반위치에 있을 때 최적한 거리임을 알 수 있다. 여러 개의 상하 전류세그먼트 코일구조를 만들어 전류세그먼트 코일구조가 자성물질인 강구를 최적한 거리에서 가속할 수 있는지 확인하였다. 강구의 질량에 대한 코일 최소 전류를 실험으로 알았고 그 결과 코일 건이나 자성물질, 자성유체에 적용 시 코일과 물질 간에 최적 거리를 해결 하였다.

• Journal of Communications and Networks
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• 제12권2호
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• pp.122-129
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• 2010

Energy conservation is one of the most important issues for evaluating the performance of wireless sensor network (WSN) applications. Generally speaking, hierarchical clustering protocols such as LEACH, LEACH-C, EEEAC, and BCDCP are more efficient in energy conservation than flat routing protocols. However, these typical protocols still have drawbacks of unequal and high energy depletion in cluster heads (CHs) due to the different transmission distance from each CH to the base station (BS). In order to minimize the energy consumption and increase the network lifetime, we propose a new hierarchical routing protocol, distance aware intelligent clustering protocol (DAIC), with the key concept of dividing the network into tiers and selecting the high energy CHs at the nearest distance from the BS. We have observed that a considerable amount of energy can be conserved by selecting CHs at the nearest distance from the BS. Also, the number of CHs is computed dynamically to avoid the selection of unnecessarily large number of CHs in the network. Our simulation results showed that the proposed DAIC outperforms LEACH and LEACH-C by 63.28% and 36.27% in energy conservation respectively. The distance aware CH selection method adopted in the proposed DAIC protocol can also be adapted to other hierarchical clustering protocols for the higher energy efficiency.

• 한국전자통신학회논문지
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• 제13권5호
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• pp.1071-1078
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• 2018

본 논문에서는 드론의 군집 비행을 위한 선행 연구를 위하여 차량 군집 시스템을 구현하였다. 초음파 센서를 이용하여 거리를 측정하였으며, 차량 간의 거리가 20cm 이하일 경우에는 정지, 30cm 이상일 경우에는 팔로우 차량이 출발함으로써 차량 간의 거리를 유지하도록 설계하였다. 주행 중, 돌발 상황으로 인하여 차량 간 거리가 40cm 이상이 될 경우에는 차량거리가 30cm 이하가 되기 전까지 팔로우 차량의 속도를 높여 거리를 줄이게 되며 30cm라는 거리를 유지하며 군집 주행을 하도록 설계하였다.