• Title/Summary/Keyword: Hybrid protocol

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Power Allocation and Mode Selection in Unmanned Aerial Vehicle Relay Based Wireless Networks

  • Zeng, Qian;Huangfu, Wei;Liu, Tong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.13 no.2
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    • pp.711-732
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    • 2019
  • Many unmanned aerial vehicle (UAV) applications have been employed for performing data collection in facilitating tasks such as surveillance and monitoring objectives in remote and dangerous environments. In light of the fact that most of the existing UAV relaying applications operate in conventional half-duplex (HD) mode, a full-duplex (FD) based UAV relay aided wireless network is investigated, in which the UAV relay helps forwarding information from the source (S) node to the destination (D). Since the activated UAV relays are always floating and flying in the air, its channel state information (CSI) as well as channel capacity is a time-variant parameter. Considering decode-and-forward (DF) relaying protocol in UAV relays, the cooperative relaying channel capacity is constrained by the relatively weaker one (i.e. in terms of signal-to-noise ratio (SNR) or signal-to-interference-plus-noise ratio (SINR)) between S-to-relay and relay-to-D links. The channel capacity can be optimized by adaptively optimizing the transmit power of S and/or UAV relay. Furthermore, a hybrid HD/FD mode is enabled in the proposed UAV relays for adaptively optimizing the channel utilization subject to the instantaneous CSI and/or remaining self-interference (SI) levels. Numerical results show that the channel capacity of the proposed UAV relay aided wireless networks can be maximized by adaptively responding to the influence of various real-time factors.

An Efficient Mobility Support Scheme based Multi-hop ARP in Wireless Mesh Networks (무선메쉬 네트워크 환경에서 다중홉 ARP 기반의 효율적인 이동성 지원)

  • Jeon, Seung-Heub;Cho, Young-Bok;Lee, Sang-Ho
    • Journal of the Korea Society of Computer and Information
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    • v.14 no.11
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    • pp.91-96
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    • 2009
  • In this paper, interoperability in heterogeneous wireless mesh network, and mesh nodes for providing efficient IP mobility technique offers multi-hop ARP. Heterogeneous wireless mesh networks to MANETs based on a wireless mesh network backbone and non-MANET architecture is based on a client wireless mesh network and the two mobile networks, combined with a hybrid wireless mesh network are separate. In two different hybrid wireless mesh network routing protocols used to connect the two protocols in the protocol conversion at the gateway to parallel processing problems seriously overload occurs. All of the network reliability and stability are factors that reduce. Therefore, for efficient integration with L3 routing protocols, design techniques to build ARP multi-hop go through the experiment to increase the number of mesh nodes, the packet forwarding rate and an increased hop number of the node was to ensure reliability and stability.

Adaptive RFID anti-collision scheme using collision information and m-bit identification (충돌 정보와 m-bit인식을 이용한 적응형 RFID 충돌 방지 기법)

  • Lee, Je-Yul;Shin, Jongmin;Yang, Dongmin
    • Journal of Internet Computing and Services
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    • v.14 no.5
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    • pp.1-10
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    • 2013
  • RFID(Radio Frequency Identification) system is non-contact identification technology. A basic RFID system consists of a reader, and a set of tags. RFID tags can be divided into active and passive tags. Active tags with power source allows their own operation execution and passive tags are small and low-cost. So passive tags are more suitable for distribution industry than active tags. A reader processes the information receiving from tags. RFID system achieves a fast identification of multiple tags using radio frequency. RFID systems has been applied into a variety of fields such as distribution, logistics, transportation, inventory management, access control, finance and etc. To encourage the introduction of RFID systems, several problems (price, size, power consumption, security) should be resolved. In this paper, we proposed an algorithm to significantly alleviate the collision problem caused by simultaneous responses of multiple tags. In the RFID systems, in anti-collision schemes, there are three methods: probabilistic, deterministic, and hybrid. In this paper, we introduce ALOHA-based protocol as a probabilistic method, and Tree-based protocol as a deterministic one. In Aloha-based protocols, time is divided into multiple slots. Tags randomly select their own IDs and transmit it. But Aloha-based protocol cannot guarantee that all tags are identified because they are probabilistic methods. In contrast, Tree-based protocols guarantee that a reader identifies all tags within the transmission range of the reader. In Tree-based protocols, a reader sends a query, and tags respond it with their own IDs. When a reader sends a query and two or more tags respond, a collision occurs. Then the reader makes and sends a new query. Frequent collisions make the identification performance degrade. Therefore, to identify tags quickly, it is necessary to reduce collisions efficiently. Each RFID tag has an ID of 96bit EPC(Electronic Product Code). The tags in a company or manufacturer have similar tag IDs with the same prefix. Unnecessary collisions occur while identifying multiple tags using Query Tree protocol. It results in growth of query-responses and idle time, which the identification time significantly increases. To solve this problem, Collision Tree protocol and M-ary Query Tree protocol have been proposed. However, in Collision Tree protocol and Query Tree protocol, only one bit is identified during one query-response. And, when similar tag IDs exist, M-ary Query Tree Protocol generates unnecessary query-responses. In this paper, we propose Adaptive M-ary Query Tree protocol that improves the identification performance using m-bit recognition, collision information of tag IDs, and prediction technique. We compare our proposed scheme with other Tree-based protocols under the same conditions. We show that our proposed scheme outperforms others in terms of identification time and identification efficiency.

Selection of Cross-layered Retransmission Schemes based on Service Characteristics (서비스 특성을 고려한 다 계층 재전송 방식 선택)

  • Go, Kwang-Chun;Kim, Jae-Hyun
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.5
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    • pp.3-9
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    • 2015
  • The wireless communication system adopts an appropriate retransmission scheme on each system protocol layer to improve reliability of data transmission. In each system protocol layer, the retransmission scheme operates in independently other layers and operates based on the parameters without reference to end-to-end performance of wireless communication system. For this reason, it is difficult to design the optimal system parameters that satisfy the QoS requirements for each service class. Thus, the performance analysis of wireless communication system is needed to design the optimal system parameters according to the end-to-end QoS requirements for each service class. In this paper, we derive the mathematical model to formulate the end-to-end performance of wireless communication system. We also evaluate the performance at the MAC and transport layers in terms of average spectral efficiency and average transmission delay. Based on the results of performance evaluations, we design the optimal system parameters according to the QoS requirements of service classes. From the results, the HARQ combined with AMC is appropriate for the delay-sensitive service and the ARQ combined with AMC is appropriate for a service that is insensitive to transmission delay. Also, the TCP can be applied for the delay-insensitive service only.

IBC-Based Entity Authentication Protocols for Federated Cloud Systems

  • Cao, Chenlei;Zhang, Ru;Zhang, Mengyi;Yang, Yixian
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.5
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    • pp.1291-1312
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    • 2013
  • Cloud computing changes the service models of information systems and accelerates the pace of technological innovation of consumer electronics. However, it also brings new security issues. As one of the important foundations of various cloud security solutions, entity authentication is attracting increasing interest of many researchers. This article proposes a layered security architecture to provide a trust transmission mechanism among cloud systems maintained by different organizations. Based on the security architecture, four protocols are proposed to implement mutual authentication, data sharing and secure data transmission in federated cloud systems. The protocols not only can ensure the confidentiality of the data transferred, but also resist man-in-the-middle attacks and masquerading attacks. Additionally, the security properties of the four protocols have been proved by S-pi calculus formal verification. Finally, the performance of the protocols is investigated in a lab environment and the feasibility of the security architecture has been verified under a hybrid cloud system.

Method for Hybrid Cooperative Sharing applied Automatic Request Protocol (자동 반복 프로토콜을 적용한 하이브리드 협력 공유 기법)

  • Kong, Hyung-Yun
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.15 no.1
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    • pp.105-110
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    • 2015
  • In cognitive radio networks, when the signal-to-noise ratio (SNR) of the link between a primary transmitter and receiver is sufficiently high, the primary transmission does not frequently demand cooperation because direct transmission of the primary communication is usually successful. Therefore, there are few opportunities for a secondary transmitter to cooperate with the primary user system in exchange for an opportunity to share the spectrum. This article proposes a scheme in which the secondary system can deliberately degrade the SNR of the primary transmission, making it so that the primary system needs cooperation from the secondary nodes, and thereby increases opportunities for spectrum sharing.

An Improved Hybrid Protocol for Software Distributed Shared Memory (소프트웨어 분산공유 메모리를 위한 향상된 하이브리드 프로토콜)

  • Lee, Seong-U;Kim, Hyeon-Cheol;Yu, Gi-Yeong;Ha, Geum-Suk
    • Journal of KIISE:Computer Systems and Theory
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    • v.27 no.9
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    • pp.777-784
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    • 2000
  • 최근 물리적으로 분산 메모리 하드웨어 상에서 공유메모리 프로그래밍 모델을 제공하는 3소프트웨어 분산 공유 메모리(Distributed Shared Memory, DSM) 시스템을 위해 여러 프로토콜이 등장하고 있다. 본 논문에서는 기존의 동적 복원 프로토콜인 하이브리드 프로토콜[11]의 성능향상을 제안하는 두 가지 문제를 밝혀내고 이를 개선하기 위한 향상된 하이브리드 프로토콜을 제안한다. 이 프로토콜은 동기화 시점에서 기존 프로토콜과 같이 과거에 어떤 페이지를 이미 접근한 프로세스에 대해서 복원 프로토콜을 적용할 뿐만 아니라. 그 페이지에 접근한 프로세스의 수가 선택된 파라미터 값 이상이면 모든 프로세스에 대해 복원 프로토콜을 적용한다. 제안한 프로토콜을 DSM 시스템인 CVM에 구현하고 100Mbps인 Ethernet으로 연결된 8대의 Sun ultral상에서 6개의 응용 프로그램에 대해 성능평가를 수행하였다. 그결과 원격 프로세스에 대한 수정정보 요구 메시지의 수를 평균 16% 감소시켰고, 4개의 응용프로그램에서 2-5%의 성능향상을 얻었다.

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Improving Efficiency of Usage Statistics Collection and Analysis in E-Journal Consortia (컨소시엄 기반 전자저널 이용통계 수집 및 분석 개선 방안)

  • Jung, Young-Im;Kim, Jeong-Hwan
    • Journal of the Korean Society for information Management
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    • v.29 no.2
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    • pp.7-25
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    • 2012
  • The proliferating use of e-journals has led increasing interest in collecting and analyzing usage statistic information. However, the existing manual method and simple journal usage reports provided by publishers hinder the effective collection of large-scale usage statistics and the comprehensive/in-depth analysis on them. Thus we have proposed a hybrid automatic method of collecting e-journal usage statistics based on screen scraping and SUSHI protocol. In addition, the generation method of summary statistics presented in graphs, charts and tables has been suggested in this study. By utilizing the suggested system and analysis data, librarians can compose various reports on budget or operation of the libraries.

Favorable Aortic Remodeling Following Serial False Lumen Procedures in a Case of Chronic Type IIIb Dissection

  • Eleshra, Ahmed Sameh;Heo, Woon;Lee, Kwang-Hun;Lee, Shin-Young;Lee, Ha;Song, Suk-Won
    • Journal of Chest Surgery
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    • v.51 no.4
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    • pp.286-289
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    • 2018
  • We report a case of acute type I aortic dissection in which an emergency graft replacement of the ascending aorta and innominate artery was performed. We performed false lumen thrombosis through hybrid thoracic endovascular aortic repair to seal the primary entry tear, followed by false lumen obliteration at the level of the descending thoracic aorta, abdominal aorta, and right common iliac artery. Over a period of 4.5 years, we used Amplatzer vascular plugs and coils based on our computed tomography angiography follow-up protocol.

Prediction of Physicochemical Properties of Organic Molecules Using Semi-Empirical Methods

  • Kim, Chan Kyung;Cho, Soo Gyeong;Kim, Chang Kon;Kim, Mi-Ri;Lee, Hai Whang
    • Bulletin of the Korean Chemical Society
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    • v.34 no.4
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    • pp.1043-1046
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    • 2013
  • Prediction of physicochemical properties of organic molecules is an important process in chemistry and chemical engineering. The MSEP approach developed in our lab calculates the molecular surface electrostatic potential (ESP) on van der Waals (vdW) surfaces of molecules. This approach includes geometry optimization and frequency calculation using hybrid density functional theory, B3LYP, at the 6-31G(d) basis set to find minima on the potential energy surface, and is known to give satisfactory QSPR results for various properties of organic molecules. However, this MSEP method is not applicable to screen large database because geometry optimization and frequency calculation require considerable computing time. To develop a fast but yet reliable approach, we have re-examined our previous work on organic molecules using two semi-empirical methods, AM1 and PM3. This new approach can be an efficient protocol in designing new molecules with improved properties.