• International Journal of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.80-87
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• 2022

Lack of sufficient battery capacity is one of the most important challenges impeding the development of wireless sensor networks (WSNs). Recent innovations in the areas of wireless energy transfer and rechargeable batteries have made it possible to advance WSNs. Therefore, in this article, we propose an energy-efficient charging of sensors in a WSN scenario. First, we have formulated the problem as an integer linear programming (ILP) problem. Then a utility function-based greedy algorithm named UGreedy/UF1 is proposed for solving the problem. Finally, the performance of UGreedy/UF1 is analyzed along with other baseline algorithms: UGreedy/UF2, 2-opt TSP, and Greedy TSP. The simulation results show that UGreedy/UF1 performs better than others both in terms of the deadline missing ratio of sensors and the total energy consumption of UAVs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.97-108
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• 2016

In this paper, we consider a cooperative monitoring network, which consists of a large number of UAVs, in order to promptly detect event in a disaster area. A command center may not be able to control each UAV individually due to resource constraints. Therefore, UAVs need to autonomously construct a mobile monitoring network in order to maximize monitoring coverage and to adapt the network formation according to environment changes in the disaster area. To that end, we propose multiple UAVs-based cooperative monitoring schemes that uses virtual forces. In this monitoring scheme, an effective monitoring is enabled by extending monitoring coverage using each UAV's circle movements. The UAVs-based monitoring network can also be splitted or merged in order to increase the monitoring effectiveness. Through simulations, we show that the proposed scheme can effectively monitor a large area and achieve a high event detection ratio.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.271-277
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• 2012

In this paper, we propose a dynamic tree formation protocol for multiple UAV which is gathering data or accomplishing a mission such as disaster monitoring, environment monitoring, and disaster relief. Especilly, we designed Hop-LQI Weight algorithm to form optimal tree in wireless dynamic environment applying situation of radio signal attenuation over distance and implemented our algorithm in MSP 430 K-mote sensor platform using TinyOS codes. We verified performance of our algorithm by comparing average link setup time by the number of nodes with minimum LQI, link cost calculation method in wireless communication.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.4
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• pp.459-466
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• 2020

The sound collected through the multi-rotor unmanned aerial vehicle (UAV) includes the ego noise generated by the motor or propeller, or the wind noise generated during the flight, and thus the quality is greatly impaired. In a multi-rotor UAV environment, both the magnitude and phase of the target sound are greatly corrupted, so it is necessary to enhance the sound in consideration of both the magnitude and phase. However, it is difficult to improve the phase because it does not show the structural characteristics. in this study, we propose a CNN-based complex spectrogram enhancement method that removes noise based on complex spectrogram that can represent both magnitude and phase. Experimental results reveal that the proposed method improves enhancement performance by considering both the magnitude and phase of the complex spectrogram.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1566-1573
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• 2016

This paper presents a beam-forming receiver with polyphase In-phase/Quadrature-phase (I/Q) network for airborne communication. In beam-forming receiver, the insertion loss (IL) difference between input path increases the receiver noise figure (NF). The major element for generating IL difference is the impedance variation of phase shifter. In order to maintain a constant IL in every phase, this paper propose a lossless polyphase I/Q network based beam-forming receiver. The proposed lossless polyphase I/Q network has low Q-factor and high impedance for drive back-end VGA (Variable gain amplifier) block with low insertion loss. The 2-stage VGA controls in-phase and quadrature-phase amplitude level for vector summation. The proposed beam-forming receiver prototype is fabricated in TSMC $0.18{\mu}m$ CMOS process. The prototype cover the $360^{\circ}$ with $5.6^{\circ}$ LSB. The average RMS phase error and amplitude error is approximately $1.6^{\circ}$ and 0.3dB.

• Journal of Korea Multimedia Society
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• v.21 no.8
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• pp.897-908
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• 2018

In this paper, we propose a security framework for a cluster drones network using the MAVLink (Micro Air Vehicle Link) application protocol based on FANET (Flying Ad-hoc Network), which is composed of ad-hoc networks with multiple drones for IoT services such as remote sensing or disaster monitoring. Here, the drones belonging to the cluster construct a FANET network acting as WTRP (Wireless Token Ring Protocol) MAC protocol. Under this network environment, we propose an efficient algorithm applying the Lightweight Encryption Algorithm (LEA) to the CTR (Counter) operation mode of WPA2 (WiFi Protected Access 2) to encrypt the transmitted data through the MAVLink application. And we study how to apply LEA based on CBC (Cipher Block Chaining) operation mode used in WPA2 for message security tag generation. In addition, a modified Diffie-Hellman key exchange method is approached to generate a new key used for encryption and security tag generation. The proposed method and similar methods are compared and analyzed in terms of efficiency.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1042-1051
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• 2011

In this paper, a total operating environment equipped with onboard wireless communication systems and ground-based mission control systems is proposed for simultaneous operation of multiple UAVs. A variety of operating structures are studied and classified systematically based on types and usages of the components. For each operating system, the strength, weakness and reliability aspects are investigated. Based on these results, a proper operating system configuration is determined and components are developed for mission formation flight. Proposed system can make a formation flight of various UAVs, execute complex missions decentralizing mission to several UAVs and cooperate several missions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.53-60
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• 2017

This paper is to design and implement the drone that supports a wideband multimedia communication and a long-range to save people in maritime. The drone is an Unnamed Aerial Vehicle (UAV) that is controlled by a radio wave not by people boarding the machine. We use the drone to respond quickly to the boating accident. To develop a smart drone for the high speed seamless video streaming in a long-range maritime, a necessary techniques are hardware design techniques that design structure of a drone, controlling techniques that operate a drone and communication techniques that control a drone in a long distance. In this paper, the limitations and techniques to design and implement the structure of drone supporting wideband multimedia communication for long-range maritime are explained. By expanding this communication drone network, it is aimed at improving utility of a drone.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.91-98
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• 2022

Unmanned aircraft system traffic management (UTM) service for the safe operation of unmanned aerial vehicles (UAV) such as drones using commercial communication networks such as long-term evolution (LTE) and 5G in low-altitude areas of 150m or less is being studied in several countries. In this paper, whether it is possible to secure three-dimensional (3D) coverage for UTM service using the existing LTE cellular network for terrestrial usersis analyzed through simulations. The practicality in the real environment is confirmed by performing performance analysis in the actual topographical environment and the LTE base station layouts in Korea. According to the analysis results, as the altitude increases, the number of line-of-sight (LOS) interference base stations increases, resulting in a worse signal to interference plus noise ratio (SINR), but coverage is secured except for the limited areas within 150m. was confirmed to be possible. In addition, it is confirmed that a significant proportion of outage areas could be reduced by placing a small number of additional base stations for the outage area.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.4244-4274
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• 2021

The utilization of UAVs in various fields has led to the development of flying ad hoc network (FANET) technology. In a network environment with highly dynamic topology and frequent link changes, the traditional routing technology of FANET cannot satisfy the new communication demands. Traditional routing algorithm, based on geographic location, can "fall" into a routing hole. In view of this problem, we propose a geolocation routing protocol based on multi-agent reinforcement learning, which decreases the packet loss rate and routing cost of the routing protocol. The protocol views each node as an intelligent agent and evaluates the value of its neighbor nodes through the local information. In the value function, nodes consider information such as link quality, residual energy and queue length, which reduces the possibility of a routing hole. The protocol uses global rewards to enable individual nodes to collaborate in transmitting data. The performance of the protocol is experimentally analyzed for UAVs under extreme conditions such as topology changes and energy constraints. Simulation results show that our proposed QLGR-S protocol has advantages in performance parameters such as throughput, end-to-end delay, and energy consumption compared with the traditional GPSR protocol. QLGR-S provides more reliable connectivity for UAV networking technology, safeguards the communication requirements between UAVs, and further promotes the development of UAV technology.