• ETRI Journal
• /
• 제35권1호
• /
• pp.51-57
• /
• 2013

In this paper, a small internal antenna for a mobile handset is presented using multiband, wideband, and high-isolation multiple-input multiple-output techniques. The proposed antenna consists of three planar inverted-F antennas (PIFAs) that operate in the global system for mobile communication (GSM900), the digital communication system (DCS), the personal communication system (PCS), the universal mobile telecommunication system (UMTS), and wireless local area network (WLAN) bands with a physical size of $40mm{\times}10mm{\times}10mm$. A resonator attached to the folded PIFA creates dual resonances, achieving a wide bandwidth of approximately 460 MHz, covering the DCS, PCS, and UMTS bands; a meander shorting line is used to improve impedance matching. Additionally, a modified neutralization link is embedded between diversity antennas to enhance isolation, which results in a 6-dB improvement in the isolation and less than 0.1 in the envelope correlation coefficient evaluated from the far-field radiation patterns. Simulation and measurements demonstrate very similar results for S-parameters and radiation patterns. Peak gains show 3.73 dBi, 3.77 dBi, 3.28 dBi, 2.15 dBi, and 5.86 dBi, and antenna efficiencies show 56.15%, 72.15%, 68.59%, 52.92%, and 82.93% for GSM900, DCS, PCS, UMTS, and WLAN bands, respectively.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
• /
• pp.192-195
• /
• 2000

GSM(Global System for Mobile Communication) system which is being used in Europe is composed A3, A5 and A8 algorithms. In this paper we implement A3 algorithm using VHDL, and verify the design by simulation. The A3 algorithm is divided into 3 parts, the encryption part, in which F-function encrypts 64 bit block data；the key generation part, which produces 32 bit subkeys；the control part, which produces the control code.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
• /
• pp.291-291
• /
• 2002

DGPS(Differential Global Positioning System) and RTK(RealTime Kinematic) is in one of today's most widely used surveying techniques. But It's use is restricted by the distance between reference station and rover station and it is difficult to process data in realtime by it's own orgnizational limitation in precise measurement of positioning. To meet these new demands, In This paper, new DGPS and RTK correction data services through Internet and PSTN(Public Switched Telephony Network) have been proposed. For this purpose, we implemented performance a DGPS and RTK error correction data transmission system for long-distance using the internet and PSTN network which allows a mobile user to increase the distance at which the rover receiver is located from the reference in realtime. and we analyzed and compared DGPS and RTK performance by experiments through the Internet and PSTN network with the distance and the time.

• 한국전자파학회논문지
• /
• 제22권2호
• /
• pp.258-264
• /
• 2011

본 논문은 GSM(Global System for Mobile communications)에서 주로 사용되는 Offset-PLL(Phase Locked Loop) 방식을 사용하여 낮은 위상 잡음과 빠른 위상 고정 시간, 우수한 불요파 특성을 갖는 주파수 합성기를 설계 제작하였다. 제안된 주파수 합성기의 구조는 3번의 주파수 하향 변환을 통해 낮은 위상 잡음 갖도록 하였으며, 높은 주파수 해상도를 갖도록 세 개의 offset 주파수중 최종 offset 주파수를 DDS(Direct Digital Synthesizer)를 이용하여 생성하였다. 또한, 빠른 스위칭 속도를 가질 수 있도록 DAC(Digital to Analog Converter)를 사용하였다. DAC 사용에 따른 위상 잡음 열화를 줄이기 위해 DAC 노이즈 제거를 위한 필터를 설계하여 성능을 개선하였다.

• 한국해양공학회지
• /
• 제23권6호
• /
• pp.53-60
• /
• 2009

Recently, since there are several problems in space, the infra-structure and the facilities in the contiguity of the existing harbors due to the trend of enlarging the container capacity of the large container vessel, a special floating platform named as the Mobile Harbor has been proposed conceptually as an effective solution of those problems. Two kinds of hull shapes, a conventional mono-hull type and a catamaran type, are proposed as midway feeders to transfer containers to the harbor on land from a large container ship on near shore. In this study, the motion response and mooring analysis are carried out for comparing the global performance of two types of Mobile Harbor. Robot arm mooring facility specially is devised and newly tried to use for the safe fixation of a large container ship and the Mobile Harbor on near shore. It would be expected for this comparison study to give a guideline to design the efficient hull form for a midway loader.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2002년도 춘계학술발표논문집 (하)
• /
• pp.1289-1292
• /
• 2002

The number of connected computers in the Internet, which has reached a state in which its address space is becoming insufficient is exponentially increased. Also nowadays modern Laptops and Mobile terminal are being used more and more. As hewn, the number of available IPv4 address is limited and many organizations have limited budget to use the global address. So the way to overcome such problems is using private addresses in their networks. In addition, the use of private address makes the system more secure. Moreover, we have considered about supporting of the scalability of data forwarding processes of nodes in their network especially Mobile IP data communication. Thus, we propose the integration of MPLS and Mobile IP network. Also we propose the security services of a constrained LSP for the MPLS payloads.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2004년도 춘계학술발표대회
• /
• pp.1529-1532
• /
• 2004

A Mobile Ad Hoc NETwork (MANET) is a collection of wireless mobile nodes that forms a temporary network without the need for any existing network infrastructure or centralized administration. Therefore, such a network is designed to operate in a highly dynamic environment due to node mobility. In mobile ad hoc network, frequent topological changes cause routing a challenging problem and without the complete view of the network topology, establishing the shortest path from the source node to the destination node is difficult. In this paper, we suggest a routing approach which utilizes location information to setup the shortest possible path between the source node and the destination node. Location information is obtained through Global Positioning System (GPS) and this geographical coordinate information of the destination node is used by the source node and intermediate nodes receiving route request messages to determine the shortest path to the destination from current node.

• 전자공학회논문지S
• /
• 제36S권6호
• /
• pp.67-75
• /
• 1999

자율분산로봇시스템에서 협조행동을 위한 로봇의 센싱과 통신 기능은 필수적이다. 일반적으로 대역적 통신시스템에서 로봇의 대수가 증가하면 통신자원의 제한과 정보의 범람이 발생한다. 따라서 이 경우 지역적 통신방법이 유리하다. 본 논문에서는 지역적 통신에 의한 정보의 전파를 해석하고 최적의 통신반경을 찾기 위한 3가지 방법을 제시한다. 또한 로봇이 정보를 획득하고 소실할 경우 발생하는 군의 카오스 행동을 피하기 위한 조건을 찾는다.

• Journal of Electrical Engineering and Technology
• /
• 제9권6호
• /
• pp.2025-2035
• /
• 2014

The read range of UHF mobile readers can be extended by a booster for mobile RFID readers (BoMR). But in an environment where multiple BoMRs are installed, the read success rate may be decreased due to signal interference. This paper proposes three arbitration methods based on interference estimation with the purpose of enhancing the read success rate. A central arbitration server manages global information in centralized arbitration method (CAM) without broadcast/multicast communication facility. In fully distributed arbitration method (FDAM), all the arbitration messages are broadcasted from a BoMR to every BoMR, and each BoMR decides with broadcasted global information. Events in FDAM are serialized naturally with broadcasted messages. Cluster Distributed Arbitration Method (CDAM) forms clusters with multicasted BoMRs and a selected BoMR acts as an arbiter in the cluster. Such effects as lengthened read range, improved the read success rates of readers can be obtained by the proposed methods without any hardware modification. In order to evaluate the arbitration methods, the RFID system is modeled by using the DEVS formalism and simulated by using the DEVSim++.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제6권6호
• /
• pp.1689-1706
• /
• 2012

The preservation of temporal dependencies among a group of processes that exchange continuous media at runtime is a key issue for emerging mobile distributed systems (MDS), such as monitoring of biosignals and interactive multiuser games. Although several works are oriented to satisfy temporal dependencies, most of them are not suitable for MDSs. In general, an MDS is characterized by the absence of global references (e.g. shared memory and wall clock), host mobility, limited processing and storage capabilities in mobile hosts, and limited bandwidth on wireless communication channels. This paper proposes an asymmetric synchronization protocol to be used at runtime in an MDS without using a common reference. One main aspect of our synchronization protocol is that it translates temporal constraints to causal dependencies of the continuous media data as seen by the mobile hosts. We simulate the protocol by considering a cellular network environment and by using MPEG-4 encoders. The simulation results show that our protocol is effective in reducing the synchronization error. In addition, the protocol is efficient in terms of processing and storage costs at the mobile devices, as well as in the overhead attached per message across the wired and wireless channels.