• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.797-799
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• 2012

The cognitive radio (CR) network has been studied in the form of open source by vast number of communities, and the potential expectation is very high since the CR is based on reprogrammable platform. However, as the peer-to-peer software has been abused, so high is the chance that the CR network can be abused public wide. Consequently, the benefit from the study of next-generation wireless network can be at risk because law breakers could abuse the CR. In this contribution, we analyze the issues and the problems of the CR and discuss an efficient measure against security attacks.

• 한국컴퓨터정보학회논문지
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• 제23권11호
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• pp.95-101
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• 2018

In this paper, we propose an efficient friendly forces location data sharing algorithm in a troops using a low bandwidth radio. The future battlefield is a 'Network Centric Warfare' with a concept of identifying the position and power of the enemy and friendly forces and leading the battlefield to victory through proper links at the time of our need. One of the basic elements in the 'Network Centric Warfare' is to share friendly forces location data. The bandwidth and transmission rates of radio used in battalion are low. Nevertheless, we should share our locations data almost in real time for effective fighting in a war situation. This paper describes the efficient method of friendly forces location data sharing based on low bandwidth radio. In particular, the concept of 'network-centered warfare' is reflected in the troop below the battalion to present an integrated and efficient way to shared location data of friendly forces.

• 한국군사과학기술학회지
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• 제25권1호
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• pp.65-71
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• 2022

In this paper, we propose an opportunistic data relay scheme in narrowband multihop combat radio networks. Narrowband networks have physical restrictions on high-speed transmission. Furthermore, the topology changes dynamically due to the jamming of the enemy, signal interference between friendly forces, and movement of network entities. Therefore, the traditional relay scheme that collects topology information and calculates a relay path before transmission is unsuitable for such networks. Our proposed scheme does not collect topology information and transmits data opportunistically. The scheme can cause unnecessary data relaying that is not related to data delivery to the destination node. However, for small networks, the effect of increasing network throughput by not gathering topology information is much greater than the effect of reducing throughput by unnecessary data relays. We demonstrate the performance superiority of the proposed scheme through simulation in the worst case of network topology.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1976-1996
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• 2011

Cognitive radio (CR) MAC protocol provides access control of unused spectrum resources without causing interference to primary users. To achieve this goal, in this paper a TDMA based cooperative multi-channel cognitive radio MAC (MCR-MAC) protocol is proposed for wireless ad hoc networks to provide reliable protection for primary users by achieving cooperative detection of incumbent system signals around the communication pair. Each CR node maintains transmission opportunity schedules and a list of available channels that is employed in the neighbor discovery period. To avoid possible signal collision between incumbent systems and cognitive radio ad hoc users, we propose a simple but efficient emergency notification message exchanging mechanism between neighbor CR nodes with little overhead. Our simulation results show that the proposed MCR-MAC can greatly reduce interference with primary users and remarkably improve the network throughput.

• 전자통신동향분석
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• 제32권6호
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• pp.66-72
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• 2017

The frequency range of a radio wave is from 3kHz to 300GHz, and radio technologies use this range to improve the quality of human lives. Radio technologies have entered a new phase of communication. The core infrastructure used as the basis for technologies leading the fourth industrial evolution, such as artificial intelligence, the Internet of Things, autonomous cars/drones, augmented reality, robots, and remote medical diagnoses, is the 5G network. The 5G network enables transmitting and receiving large amounts of data at very high speed. In particular, application technologies with artificial intelligence have been studied, including radar, wireless charging, electromagnetic devices and their effects on humans, EMI/EMC, and microwave imaging. In this study, we present a future radio technology that is needed to prepare for the upcoming industrial revolution and digital transformation.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.210-215
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• 2003

At present, communication network for subway is making use of the train radio system for main network and normally established a base station every three subway station. It is talk over the telephone between a locomotive and the traffic control for careful train service. Besides, mobile telephone equipment is using for service improve and convenience to passengers such as 011, 016, 017, 019 and what not. However, the train radio system has been occurring a various problems when a state of emergency because it is able to compose only one communication route each base station zone. We could have improving like this problems through induce the TRS(Trunked Radio System), though because have been able to compose multilateral communication route in case of linking with LCX(Leaked Coaxial) cable which is established. Therefore, we could be able to a fitting meet the emergency as train firing etc.. and efficient use of limited frequency resources.

• 천문학회보
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• 제37권2호
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• pp.239.2-239.2
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• 2012

We report preliminary results of MOGABA project for monitoring total flux density, linearly polarized flux, and polarization angle at 22, 43 and 86GHz of Gamma-ray bright AGN (Active Galactic Nuclei) with KVN (Korean VLBI Network) 21-m radio telescopes. The project has been conducted in one year since May 2011 with an effective monitoring cycle of 1 week, observing four main objects (3C 454.3, BL Lac, 3C 273, and 3C 279). More objects were included in the source list when they had flared in Gamma-ray. Especially, we included a compact radio source at the Galactic center, SgrA* since Jan. 2012. In this paper, we report the current status of the project and preliminary results for the monitoring observations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권5호
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• pp.1755-1777
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• 2022

The development of wireless communication technology has led to the underutilization of radio spectra. To address this limitation, an intelligent cognitive radio network was developed. Specific emitter identification (SEI) is a key technology in this network. However, in realistic non-cooperative scenarios, the system may detect signal classes beyond those in the training database, and only a few labeled signal samples are available for network training, both of which deteriorate identification performance. To overcome these challenges, a meta-learning-based open-set identification system is proposed for SEI. First, the received signals were pre-processed using bi-spectral analysis and a Radon transform to obtain signal representation vectors, which were then fed into an open-set SEI network. This network consisted of a deep feature extractor and an intrinsic feature memorizer that can detect signals of unknown classes and classify signals of different known classes. The training loss functions and the procedures of the open-set SEI network were then designed for parameter optimization. Considering the few-shot problems of open-set SEI, meta-training loss functions and meta-training procedures that require only a few labeled signal samples were further developed for open-set SEI network training. The experimental results demonstrate that this approach outperforms other state-of-the-art SEI methods in open-set scenarios. In addition, excellent open-set SEI performance was achieved using at least 50 training signal samples, and effective operation in low signal-to-noise ratio (SNR) environments was demonstrated.

• 컴퓨터교육학회논문지
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• 제5권3호
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• pp.19-25
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• 2002

무선 네트웍 환경에서 블루투스는 휴대폰, PDA, 휴대용PC 등과 같은 휴대장치들, 네트워크 액세스 포인트, 기타 주변장치들 간에 좁은 영역내의 무선 연결을 위한 기술사양으로서 크기가 작고, 저렴한 가격, 적은 전력소모로 이용가능한 근거리 무선통신이다. 블루투스는 1개의 마스터와 최대 7개의 슬레이브를 갖는 피코넷으로 구성되며, 다수의 피코넷이 모여 하나의 스캐터넷으로 구성하게 된다. 본 논문에서는 노드수에 따른 효과적인 스캐터넷의 형성과 메카니즘 구성을 위해 라인형 및 링형 스캐터넷을 구성하고, 이에 대한 성능평가를 NS기반의 Bluehoc 시뮬레이터를 통하여 구현하고, 라인형 및 링형 스캐터넷의 특성을 비교 분석하여 최적의 무선네트웍 환경을 구성하고자 한다.

• Journal of Communications and Networks
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• 제18권3호
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• pp.340-350
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• 2016

The performance of large-scale cognitive radio (CR) networks with secondary users sustained by opportunistically harvesting radio-frequency (RF) energy from nearby primary transmissions is investigated. Using an advanced RF energy harvester, a secondary user is assumed to be able to collect ambient primary RF energy as long as it lies inside the harvesting zone of an active primary transmitter (PT). A variable power (VP) transmission mode is proposed, and an energy-based opportunistic spectrum access (OSA) strategy is considered, under which a secondary transmitter (ST) is allowed to transmit only if its harvested energy is larger than a predefined transmission threshold and it is outside the guard zones of all active PTs. The transmission probability of the STs is derived. The outage probabilities and the throughputs of the primary and the secondary networks, respectively, are characterized. Compared with prior work, the throughput can be increased by as much as 29%. The energy-based OSA strategy can be generally applied to a non-CR setup, where distributed power beacons (PBs) are deployed to power coexisting wireless signal transmitters (WSTs) in a wireless powered sensor network.