• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.1
• /
• pp.85-92
• /
• 2002

In this study, we analyzed and experimented micro-strip line inductors and capacitors for a SAW duplexer, an important devise for mobile communication. For SAW duplexers, micro-strip line lumped elements must have small impedance values, below several tens of nH or several tens of pF, and a small area pattern. In this study, we performed theoretical analysis of flat line type, meander line type, and spiral line type inductors and interdigital capacitors on a LiTaO$_3$ Piezo-crystal. We proposed a measurement method to evaluate small values of lumped elements accurately with network analyzer. In experiments, we confirmed validity of the theoretical analysis method through fabrication and characterization of micro-strip line lumped elements. The analysis method in this paper can be applied to SAW duplexers well as other microwave devices.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.2 no.3
• /
• pp.325-333
• /
• 1998

In this paper, conventional STM(Synchronous Transfer Mode) supports another traffics by using idle channels. Proposed mobile terminals are distributed independently at the BSA(Basic Service Area). So, MAC(Medium Access Control) specified on the wireless ATM networks, which is managing statistics multiplewing functions, idle channel's ultilization is maximized and multimedia service characteristic for conventional wired networks based fixed assignment scheme(connection-oriented) and random assignment scheme(connection-oriented) improving on dynamic reservation based MAC protocol.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.07a
• /
• pp.382-384
• /
• 2005

현재 무선 네트워크를 통한 패킷 데이터 서비스의 수요가 증가하고 있다. CDMA2000 이동통신망의 패킷데이터 서비스는 넓은 영역을 커버하는 대신에 비용이 높고 대역폭이 낮다. 반면에 802.11b 무선 LAN의 경우 작은 지역만을 커버할 수 있지만 대역폭이 크고 비용이 낮은 특성이 있다. 따라서 무선 LAN과 CDMA2000 이동통신망과 효율적으로 연동하여 사용한다면 많은 성과를 얻을 수 있다. 이에 본 논문은 기존 CDMA2000 이동통신망과 무선 LAN의 효율적인 연동을 통해서 끊김 없는 서비스를 받을 수 있는 이중모드 단말의 구현을 제안한다. 본 논문에서 제안하는 이중모드 단말은 무선 네트워크의 상태를 파악하여 네트워크를 선택하고 자동으로 연결을 관리한다. 또한 끊김 없는 핸드오프를 위한 동작을 통해 사용자가 끊김 없는 데이터 서비스를 받을 수 있도록 한다.

• IE interfaces
• /
• v.19 no.1
• /
• pp.1-8
• /
• 2006

The mobile communication network has to offer good quality of services (QoS), high capacity, and more coverage at a lower cost. However, with the increase of cellular user, the shortage of capacity due to unbalanced call distribution and lack of QoS are common. This paper deals with dynamic sectorization for efficient resource management to solve load unbalancing among microcells in CDMA (Code Division Multiple Access) microcellular system. Dynamic load balancing can be effected by grouping micro-cells properly and grouping can be developed through a routing mechanism. Therefore, we use ants and their routes to choose the optimum grouping of micro-cells into sectors using Multiple Ant Colony System (MACS)in this paper.

• Journal of information and communication convergence engineering
• /
• v.9 no.4
• /
• pp.405-410
• /
• 2011

In this paper, a conflict-avoided resource reservation scheme for UWB (Ultra Wide Band) WPAN (Wireless Personal Area Network) with D-MAC (Distributed Medium Access Control) is proposed. Since distributed characteristic of the WiMedia D-MAC supporting DRP (Distributed Reservation Protocol) scheme may cause lots of conflicts, overall performances of the WiMedia D-MAC can be deteriorated. In addition, once a DRP conflict occurs, only one of the DRP reservations involved in that DRP conflict maintains the reserved MASs, while the other DRP reservation must be terminated and DRP negotiations for them have to be re-started. Such DRP termination and renegotiation time delays due to the DRP conflicts can be a critical problem to the mobile devices transceiving real-time QoS traffic streams. Therefore, we propose a mechanism to avoid DRP conflicts by providing a kind of path diversity using relay transmission scheme and demonstrate its performance improvements via simulation results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.05a
• /
• pp.73-75
• /
• 2010

Current communication and broadcasting services are moved to integrated convergence service. So IPTV(Internet Protocol based TeleVision) services are growth rapidly. Traditional TV were provide simplex service. but IPTV will provide duplex service that is possible of interaction with TV and audience. Therefore current researches are focusing the Social TV service. at this point, we see the trend of Social TV system for research and implementation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.10
• /
• pp.2579-2585
• /
• 2014

Location-Based Services can be defined as services that integrated a mobile network device's position with other information so as to provide added value to users. One of the most important elements in the LBS is the ability to locate objects. In this paper, the positioning techniques using radio signal were introduced, and the positioning principles and accuracies for LBS of smart phone were analyzed. As a result, the some techniques for improving user security were suggested.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.11 no.4
• /
• pp.19-38
• /
• 2007

Graph theory is becoming increasingly significant as it is applied of mathematics, science and technology. It is being actively used in fields as varied as biochemistry(genomics), electrical engineering(communication networks and coding theory), computer science(algorithms and computation) and operations research(scheduling). The powerful results in other areas of pure mathematics. Rhis paper, besides giving a general outlook of these facts, includes new graph theoretical proofs of Fermat's Little Theorem and the Nielson-Schreier Theorem. New applications to DNA sequencing (the SNP assembly problem) and computer network security (worm propagation) using minimum vertex covers in graphs are discussed. We also show how to apply edge coloring and matching in graphs for scheduling (the timetabling problem) and vertex coloring in graphs for map coloring and the assignment of frequencies in GSM mobile phone networks. Finally, we revisit the classical problem of finding re-entrant knight's tours on a chessboard using Hamiltonian circuits in graphs.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04d
• /
• pp.394-396
• /
• 2003

비동기식 제 3 세대 이동통신 시스템인 GPRS 망은 기존의 제 2 세대 통신인 GSM(Global System for Mobile Communication)방식에 GGSN(Gateway GPRS Support Node)과 SGSN(Serving GPRS Support Node)노드를 추가함으로써 패킷 교환 방식을 가능하게 하였다. GPRS 망에서 멀티미디어 서비스들의 QoS 제공을 위하여, GPRS 망과 인터넷 망을 연결시켜주는 관문(Gateway) 역할을 수행하는 GGSN 노드의 실시간 트래픽들에 대한 처리 능력 분석이 필수적이다. 따라서. GGSN에서 클래스별 QoS 보장을 위한 정확한 성능 분석이 필요하다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.910-913
• /
• 2012

통신기술의 발달과 스마트 폰의 급격한 보급으로 인하여 모바일 환경은 음성 데이터 기반의 환경에서 인터넷 데이터 기반의 환경으로 급격히 변화되었다. 이로 인하여 음성 서비스 처리 위주의 음성 데이터 기반 모바일 환경은 대용량 동영상 서비스, 인터넷, 메신저 등의 유선 네트워크 환경과 같은 다양한 서비스가 요구되는 환경으로 변화되었다. 이러한 환경 변화로 인하여 모바일 네트워크는 무선 네트워크상의 취약점 뿐 만 아니라 유선환경의 네트워크 취약점을 동시에 지니는 환경으로 변화되었고, 이로 인한 다양한 새로운 취약점들이 부각되기 시작하였다. 본 논문에서는 이와 같이 새롭게 부각되고 있는 모바일 Packet Switched Core Network(PSCN) 환경에서 Service Provider(SP)의 Service Recover로 인해 유발되는 Paging Table Denial of Service(PT-DoS)를 효율적으로 제어하기 위한 Delay Access Control(DAC) 기반의 QoS를 이용한 방법을 설계/구현하였다. 그리고 실험을 통해, PT-DoS를 차단하여 PSCN 공격을 미연에 방지하는 효과를 확인하였다.