• ETRI Journal
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• 제32권2호
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• pp.292-301
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• 2010

Increasing convergence among heterogeneous radio networks is expected to be a key feature of future ubiquitous services. The convergence of radio networks in combination with dynamic spectrum allocation (DSA) could be a beneficial means to solve the growing demand for radio spectrum. DSA might enhance the spectrum utilization of involved radio networks to comply with user requirements for high-quality multimedia services. This paper proposes a simple spectrum allocation algorithm and presents an analytical model of dynamic spectrum resource allocation between two networks using a 4-D Markov chain. We argue that there may exist a break-even point for choosing whether or not to adopt DSA in a system. We point out certain circumstances where DSA is not a viable alternative. We also discuss the performance of DSA against the degree of resource sharing using the proposed analytical model and simulations. The presented analytical model is not restricted to DSA, and can be applied to a general resource sharing study.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권12호
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• pp.5669-5684
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• 2018

The new mobile edge network architecture has been required for an increasing amount of traffic, quality requirements, advanced driver assistance system for autonomous driving and new cloud computing demands on highway. This article proposes a hierarchical cloud computing architecture to enhance performance by using adaptive data load distribution for buses that play the role of edge computing server. A vehicular dynamic cloud is based on wireless architecture including Wireless Local Area Network and Long Term Evolution Advanced communication is used for data transmission between moving buses and cars. The main advantages of the proposed architecture include both a reduction of data loading for top layer cloud server and effective data distribution on traffic jam highway where moving vehicles require video on demand (VOD) services from server. Through the description of real environment based on NS-2 network simulation, we conducted experiments to validate the proposed new architecture. Moreover, we show the feasibility and effectiveness for the connected car media service on highway.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권4호
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• pp.805-821
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• 2011

Wireless Sensor Networks (WSNs) are rapidly emerging because of their potential applications available in military and civilian environments. Due to unattended and hostile deployment environments, shared wireless links, and inherent resource constraints, providing high level security services is challenging in WSNs. In this paper, we revisit various security attack models and analyze them by using a well-known standard notation, Unified Modeling Language (UML). We provide a set of UML collaboration diagram and sequence diagrams of attack models witnessed in different network layers: physical, data/link, network, and transport. The proposed UML-based analysis not only can facilitate understanding of attack strategies, but can also provide a deep insight into designing/developing countermeasures in WSNs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권3호
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• pp.1321-1332
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• 2016

Wireless sensor networks (WSN) are self-organized networks that typically consist of thousands of low-cost, low-powered sensor nodes. The reliability and availability of WSNs can be affected by faults, including those from radio interference, battery exhaustion, hardware and software failures, communication link errors, malicious attacks, and so on. Thus, we propose a novel multi-agent fault tolerant system for wireless sensor networks. Since a major requirement of WSNs is to reduce energy consumption, we use multi-agent and mobile agent configurations to manage WSNs that provide energy-efficient services. Mobile agent architecture have inherent advantages in that they provide energy awareness, scalability, reliability, and extensibility. Our multi-agent system consists of a resource manager, a fault tolerance manager and a load balancing manager, and we also propose fault-tolerant protocols that use multi-agent and mobile agent setups.

• 한국컴퓨터정보학회논문지
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• 제8권2호
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• pp.122-128
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• 2003

무선인터넷을 개발하는 방법은 여러 가지 개발방법이 있다. 그 중 대표적인 것으로 WAP(Wireless Application Protocol) 기반 서비스와 자바 기반 서비스가 있다. WAP 기반은 사용자에게 한정된 편이성을 제공하지만 자바 기반의 무선 인터넷은 사용자에게 많은 편이성과 GUI(Graphic User Interface)를 지원하여 쉽게 접근 할 수 있게 한다. 본 논문에서는 WAP 기반 애플리케이션 개발방법과 자바 기반 애플리케이션 개발 방법을 제시하며, 실험을 통해 두 시스템간의 성능을 비교한다.

• 한국멀티미디어학회논문지
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• 제24권9호
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• pp.1211-1223
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• 2021

Internet of Things(IoT) services have increased the demand for connectivity among electronics devices. As a result, various types of novel wireless communication technologies have been standardized and developed. In this paper, we evaluate the performance of low power wireless communication technologies such as Bluetooth, IEEE 802.15.4, DASH 7, IEEE 802.15.4g, LoRa, and SigFox in various environments. This is the first experiment evaluating various low power wireless communication technologies in real testbed. We expect that the evaluation results will be useful data to other researchers in applying the IoT technology in the future.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.107-114
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• 2023

In this paper, the results of experiments conducted in indoor wired and outdoor wireless environments to reduce the interference impact of 5G mobile communication on fixed satellite services using RF Interference Reduction Module (IRM) are presented. Test results for interference signals with a 100MHz bandwidth in a wired environment demonstrate that RF IRM can reduce interference by more than 20dB in a 100MHz bandwidth. The performance of RF IRM was also tested in the S-band wireless environments. In the S-band wireless environments with interference signals having a 20MHz bandwidth, RF IRM exhibits interference reduction performance of 12-15dB, for signals with a 50MHz bandwidth, it shows 10-12dB interference reduction, and for signals with a 100MHz bandwidth, it demonstrates 5-10dB interference reduction. This paper shows that RF IRM can be used not only within transceivers but also in wireless environments to mitigate interference.

• 한국인터넷방송통신학회논문지
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• 제11권6호
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• pp.177-182
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• 2011

최근 연안지역에 선박 통항량, 다양한 양식업, 어로, 그리고 레저 활동이 증가하고 있어, 이에 따라 안전한 항해 통신 정보를 위한 다양한 통신 서비스가 요구되어 왔다. 본 논문은 다중 인터페이스를 가진 이동 IP 라우터를 이용한 해안 지역에서 통신 서비스 지원 방안에 관한 것이다. 이를 위하여, 이 시스템은 선박에게 다양한 통신 서비스를 제공할 수 있는 WiBro, HSDPA, 그리고 WLAN와 같은 무선 인터페이스를 가지고 있어, 해안을 따라서 설치된 무선망을 통하여 선박에게 다양한 정보통신 서비스를 실시간으로 제공할 수 있다. 따라서 이 시스템은 공인된 끊김 없는 정보 통신 서비스를 제공할 수 있는 인프라를 제공할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2093-2095
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• 2002

Nowadays, there are actually lots of changes in wireless communications of Korea. But it is not an exact PTP(Peer to Peer) Communication. In other words, a mobile station which can find fixed station can be connected with wireless internet server or other services, oppositely fixed station cannot approach to mobile station. Even though it exists, it is difficult to communicate with full duplex. We can service using CDMA 1X techniques such as cellular based SMS (Short Message Service) service or very simple MPRG Services. In this paper, we propose a system, using DirectX based mobile/fixed station stand alone program, depending on bandwidth of wireless service provider, tranceiving high resolution moving picture or reliable data regularly by a fixed connection each other.

• 한국공간정보시스템학회 논문지
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• 제5권1호
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• pp.75-81
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• 2003

인터넷을 기반으로 하는 정보방송 서비스가 널리 확대되고 있으나, 인터넷 프로토콜 고유의 한계로 인해 사용상에 제한이 있다. 본 논문에서는 기지국에 IP 주소변환 기능을 도입한 억세스망에서의 인터넷방송 기술과 이를 이용한 위치기반서비스가 제안되었다. 수신기에 IP 주소가 할당되지 않아도 되며, 사전에 서버의 주소를 몰라도 정보를 수신할 수 있으며, 서버의 부하나 통신망 트래픽이 대폭 감소되는 장점이 있다.