• Journal of the Korea Institute of Information and Communication Engineering
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• v.27 no.1
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• pp.62-68
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• 2023

An aerial relay system utilizing an unmanned aerial vehicle(UAV) or drone is addressed for event-driven operations such as temporary communication services for disaster affected area, military and first responder support. UAV relay system (URS) targets to provide a reliable communication service to a remote user equipment or an operator, therefore, a fast UAV placement to guarantee a minimum quality of service(QoS) is important when an operation is requested. Researches on UAV utilization in communication systems mostly target to derive the optimal position of UAV to maximize the performance, however, fast deployment of UAV is much more important than optimal placement under emergency situations. To this end, this paper derives the feasible area for UAV placement, investigates the effect of performance requirements on that area, and suggests UAV placement to certainly guarantee the performance requirements. Simulation results demonstrate that the feasible area derived in this paper matches that obtained by an exhaustive search.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.1
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• pp.21-30
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• 2020

In this paper, we predicted the propagation loss for the air-to-ground (A2G) channel between the ground control system and the unmanned aerial vehicle (UAV) using the prediction model for the aircraft recommended by the International Telecommunication Union (ITU). We analyzed the network coverage of the aerial relay system based on the medium altitude UAVs by expanding it into the air-to-air (A2A) channel. Climate and geographic factors in Korea were used to predict propagation loss due to atmospheres. We used the measured data published by the Telecommunication Technology Association (TTA) for regional rainfall-rate and effective earth radius factors to increase accuracy. In addition, the aerial relay communication system used the key parameter of the common data link (CDL) system developed in Korea recently. Prediction results show that the network coverage of the aerial relay system broadens at higher altitude.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1574-1580
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• 2021

This paper designs and presents the results of an air network simulation radio transmission link applied with a multi-beam active phase array antenna simulator in a testbed system for verifying an air network currently underway as a technology development task. Using the Ku band, the Radio transmission link was designed in consideration of the link budget to satisfy the requirements for the system being developed. Considering short-distance links and long-distance links, the required EIRP and G/T performance scales of multi-beam repeaters and mission planes were applied to confirm the minimum and maximum link margins based on Eb/No. In this Radio Transmission Link design, the application analysis results such as rainfall availability are used to effectively establish standards when selecting the operating radius of the multi-beam relay system and related system standards.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.422-429
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• 2022

In this paper, the intermediate frequency transmission signal level between the network system-based baseband and RF unit consisting of multi-channel airborne relay devices and a lot of mission devices, which are currently undergoing technology development tasks, is kept constant at the reference signal level. Considering the other party's receiving input range, despite changes in the short-range long-range wireless communication environment, it presents a multi-link protection and MLP-A algorithm that allows signals to be transmitted stably and reliably through signal detection automatic gain control, and experiments and analysis considering short-distance and long-distance wireless environments were performed by designing, manufacturing, and implementing RF units to which MLP-A algorithms were applied, and applying distance calculation equations to the configuration of multiple air movements and verification networks. Through this, it was confirmed that a stable and reliable RF communication system can be operated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2102-2112
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• 2015

In this paper, we propose a new positioning scheme for accuracy improvement of Relay-based Navigation System. The conventional relay-based system occurs larger vertical error than horizontal one due to structural characteristics that positioning references are located toward same direction and a location of user is estimated by triangulation technique. In the proposed positioning scheme, the user position is reestimated using an additional virtual reference which is generated based on position information of reference stations in navigation signals and estimated initial user position. The nearest reference station from the estimated user position is selected as a virtual reference to minimize the effect of geometrical factor. The vertical error decreases by using reference points on multi planes, therefore, accurate positioning is possible than the conventional scheme. We demonstrated that the accuracy of a user is improved through simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.123-125
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• 2015

Wireless ad hoc network which is comprised of wireless nodes that have the limited communication range is utilized to monitoring disaster area, tracing object, and tactical system. But in the case of wireless node on the ground, a network performance decrease because wireless channel is affected from obstacle or the node deployment is restricted. In this paper, we consider wireless network based on UAV(Unmanned Aerial Vehicle) which has little spatial constraint and quickly deploy a position. We implement test-bed included ground nodes and UAV, and measure throughput and PDR(Packet Delivery Ratio) according to the usage of UAV. We show that network performance is improved by relaying data on UAV.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.430-436
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• 2014

This paper relates to the study about the street security light management system. The purpose of the wireless remote management system is to manage street security lights efficiently. The system is composed of three components like light controller, CDMA gateway and web based remote management server. The zigbee solution is adopted to make local wireless network between street security lights. The CDMA network is used for the wireless communication between street security light controller and the remote control center. The gateway to interconnect zigbee network and CDMA was designed with low power 32 bits Cortex M3 micro-controller. For the data communication between the management server and the gateway, SMS and socket based TCP streaming is used. The management server sends SMS to the gateway to deliver light control and management requests, and the gateway replies with the light controllers report via TCP streaming. By using both SMS and TCP streaming communication, it was verified that simple cost effective management is possible for street security lights. We tried real test for 95 street security lights in real environment during two months and analyzed the practical possibility for mass supply.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.1134-1147
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• 1998

Remote management and control system for LMDS wireless CATV network which is being developed at SK Telecom is developed. This system is composed of central control division located at head center and remote units for remote transceivers equipped in base stations and repeaters. It monitors the state of the remote transceivers and controls the operations using PSTN for iterface. Remote transceivers whould be equipped in pairs, and the operations are exchanged automatically in case of emergency situations. the remote units are designed not only to perform commands form central control division, bet to inform emergency situations such as disorder and power failure. This system works well, which is established at Central research center in SK Telecom with remote units such as BTX, PPTX, and PPRX. This system could be utilized in other applications requiring remote control through sligh modifications.