• Journal of Communications and Networks
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• 제14권2호
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• pp.179-187
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• 2012

Power saving is one of the most important features that extends the lifetime of portable devices in mobile wireless networks. The IEEE 802.16e mobile broadband wireless access system adopts a power saving mechanism with a binary truncated exponent algorithm for determining sleep intervals. When using this standard power saving scheme, there is often a delay before data packets are received at the mobile subscriber station (MSS). In order to extend the lifetime of a MSS, the battery energy must be used efficiently. This paper presents a dynamically alternating sleep interval scheduling algorithm as a solution to deal with the power consumption problem. We take into account different traffic classes and schedule a proper sequence of power saving classes. The window size of the sleep interval is calculated dynamically according to the packet arrival rate. We make a tradeoff between the power consumption and packet delay. The method achieves the goal of efficiently reducing the listening window size, which leads to increased power saving. The performance of our proposed scheme is compared to that of the standard power saving scheme. Simulation results demonstrate the superior performance of our power saving scheme and its ability to strike the appropriate performance balance between power saving and packet delay for a MSS in an IEEE 802.16e mobile broadband wireless access system.

• 한국통신학회논문지
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• 제31권11A호
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• pp.1101-1112
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• 2006

무선 환경에서의 이동 중 고속의 멀티미디어 서비스 제공에 대한 수요가 증가하면서 (Wireless Broadband internet) 시스템과 같은 MBWA (Mobile Broadband Wireless Access) 기술에 대한 관심이 점차 증가하고 있다. 이러한 WiBro 시스템은 기존의 셀룰라(Cellular) 시스템 기반의 이동 통신망과는 달리 기본적으로 IP 기반의 백본 네트워크로 구성될 것이며 ALL-lP로의 망 진화의 흐름에 따라서 궁극적으로는 IPv6 (IP version six) 기반의 백본 네트워크로 도입될 것이다. 이와 같은 무선 이동 환경에서는 WiBro 시스템의 물리 계층이나 매체 접근 제어 계층에서의 이동성 지원 방안뿐만 아니라 네트워크 계층에서의 이동성 지원 프로토콜 지원이 필요하다. 따라서 본 논문에서는 IPv6 기반의 WiBro 시스템에서 단말의 서브넷 (Subnet) 간 핸드오버 성능을 향상시키기 위한 고속 핸드오버 방안을 제안하고 모의실험을 통해서 제안한 메카니즘 (Mechanism)이 서브넷 간 핸드오버 시 발생할 수 있는 데이터 유실 문제와 핸드오버 지연 발생 문제 등을 개선할 수 있다는 것을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권4호
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• pp.1832-1853
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• 2018

The personal health record (PHR) system is a promising application that provides precise information and customized services for health care. To flexibly protect sensitive data, attribute-based encryption has been widely applied for PHR access control. However, escrow, exposure and abuse of private keys still hinder its practical application in the PHR system. In this paper, we propose a coordinated ciphertext policy attribute-based access control with user accountability (CCP-ABAC-UA) for the PHR system. Its coordinated mechanism not only effectively prevents the escrow and exposure of private keys but also accurately detects whether key abuse is taking place and identifies the traitor. We claim that CCP-ABAC-UA is a user-side lightweight scheme. Especially for PHR receivers, no bilinear pairing computation is needed to access health records, so the practical mobile PHR system can be realized. By introducing a novel provably secure construction, we prove that it is secure against selectively chosen plaintext attacks. The analysis indicates that CCP-ABAC-UA achieves better performance in terms of security and user-side computational efficiency for a PHR system.

• 한국통신학회논문지
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• 제32권3A호
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• pp.261-270
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• 2007

실시간과 비실시간 서비스 클래스의 각 QoS요구 사항을 만족하면서 전체 시스템 용량을 최대화하기 위하여 DTPQ스케줄링 알고리즘이 제안된 바 있다. 기존 DTPQ방식은 개별 서비스 클래스의 QoS를 만족하면서 전체 시스템의 평균 수율을 극대화하기 위해 실시간 서비스의 HOL 패킷의 지연 시간이 정해진 임계값을 넘는 경우에만 서비스하는 접근으로서, 이를 구현하기 위해서는 주어진 환경에서 적절한 지연 임계값을 설정할 수 있어야 한다. 본 논문에서는 실시간 사용자의 채널 상태와 지연 시간에 따라 지연 임계값을 적응적으로 적용하는 A-DTPQ 기반의 스케줄링 기법을 제안한다. 이는 기존의 DTPQ알고리즘과 달리 트래픽 부하 및 채널 특성 등에 따라 지연 임계값을 적응적으로 결정하는 방식이다. 시스템 레벨 시뮬레이션을 통해 제안 방식의 고정된 최적 임계값을 가지는 DTPQ방식보다 성능이 향상시킬 수 있음을 확인하였으며, 향후 연구에서는 다양한 서비스 클래스에 대해 이와 같은 개념을 일반화할 수 있을 것이다.

• ETRI Journal
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• 제26권1호
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• pp.48-52
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• 2004

In this letter, we consider a new packet scheduling algorithm for an orthogonal frequency division multiplexing access/frequency division duplex (OFDMA/FDD)-based system, e.g., mobile broadband wireless access or high-speed portable internet systems, in which the radio resources of both time and frequency slots are dynamically shared by all users under a proper scheduling policy. Our design objective is to increase the number of non-realtime service (e.g., WWW) users that can be supported in the system, especially when the minimum bit rate requirement is imposed on them. The simulation results show that our proposed algorithm can provide a significant improvement in the average outage probability performance for the NRT service, i.e., significantly increasing the number of NRT users without much compromising of the cell throughput.

• ETRI Journal
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• 제26권3호
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• pp.265-268
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• 2004

We develop a simple exact solution method for return link capacity allocation scheduling in a satellite interactive network using a hybrid code-division multiple access / time-division multiple access (CDMA/TDMA) scheme.

• ETRI Journal
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• 제35권2호
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• pp.234-244
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• 2013

Internet protocol television (IPTV) service depends on the network quality of service (QoS) and bandwidth of the broadband service provider. IEEE 802.16j mobile multihop relay Worldwide Interoperability for Microwave Access networks have the opportunity to offer high bandwidth capacity by introducing relay stations. However, to actually satisfy QoS requirements for offering IPTV services (HDTV, SDTV, Web TV, and mobile TV) for heterogeneous users' requests, providers must use a video server for each IPTV service type, which increases the network load, especially bandwidth consumption and forwarding time. In this paper, we present a solution for forwarding IPTV video streaming to diverse subscribers via an 802.16j broadband wireless access network. In particular, we propose a new multicast tree construction and aggregation mechanism based on the unique property of prime numbers. Performance evaluation results show that the proposed scheme reduces both bandwidth consumption and forwarding time.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.956-961
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• 2009

When construction engineers perform their work in the jobsite, they have to record as-built conditions in the project log (Data Collection). On the other hand, the engineers often have to refer to the construction documents when necessary at the job faces (Data Access). The practice of Data Collection and Data Access in the jobsite can be greatly enhanced by utilizing mobile computing with wireless communications. In this paper, two cases of mobile computing applications for construction field management are presented; Mobile Specifications System and Mobile Data Collection System. The demonstration of the process for developing two mobile applications is the primary purpose of the paper. The problems and issues involved with adopting mobile computing for construction field are also presented. The simple information framework for mobile computing has been also proposed as an outcome of the research. As for development tools, readily available relational database and wireless network have been used. The use of commercial mobile broadband was examined for data communication where local area network is not available.

• 정보처리학회논문지C
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• 제12C권6호
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• pp.809-816
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• 2005

MANET(mobile ad hoc network)은 BcN(broadband convergence network)의 액세스 망 중의 하나가 될 수 있으며 이를 통해 접속되는 사용자 노드는 코어망에 멀티홉으로 접속되am로 기존과 다른 새로운 주소 자동 설정 기능이 요구된다. 이에 관련하여 기존 유선 BcN 기반 자동 주소 설정 방식에서 단말의 이동성을 감안한 독립형 MANET의 자동 주소 할당 방식들이 제안되었으나 내부 BcN 망과 연결되는 형태의 액세스 망으로서의 MANET에 관한 주소 설정 방식은 고려되지 않고 있다. 본 논문에서는 뚜선 노드들이 BcN 게이트웨이를 통해 BcN 코어망에 접속할 수 있는 하이브리드 MANET 환경에서의 전역 주소의 할당 기능이 포함된 새로운 자동 주소 할당 방식을 제안하였다. 제안된 방법은 기존 IPv6 NDP(neighbor discovery protocol) 메시지 및 추가 확장을 통해 전역 주소에 사용되는 프리픽스 정보를 모든 모바일 노드들에게 전달할 수 있도록 했으며, 메시지 브로드캐스팅을 사용하지 않음으로써 네트워크 성능에 주는 영향을 최소화하였다.

• Journal of Communications and Networks
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• 제2권1호
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• pp.35-45
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• 2000

this paper presents the concept of "mobile ATM', a proposal for third-generation (3G) mobile communication network infrastructure capable of supporting flexible evolution of radio technologies from today's cellular and data services towards future wireless multimedia services. Mobile ATM provides generic mobility management and QoS-based transport capabilities suitable for integration of multiple radio access technologies including cellular voice. wireless data, and future broadband wireless services. The architecture of a mobile ATM network is outlined in terms of the newly-defined "W-UNI" interface at the radio link and "M-UNI"and "M-UNI" interface which supports unified access for WATM and non-ATM mobile terminals through corresponding interworking functions (IWF) is explained. leading to an understanding of how different radio access technologies are supported by the same ATM-based core network infrastructure. Generic mechanisms for handoff and location management within the core mobile network are discussed. and related protocol extensions over the "W-UNI" and "M-UNI/NNI"interfaces are proposed. the issue of "crossover switch (COS)" selection in mobile ATM is considered, and a unified handoff signaling syntax which supports flexibility in COS selection is described. Typical signaling sequences for call connection and handoff using the proposed protocols are outlined. Experimental results form a proof-of-concept mobile ATM network prototype are presented in conclusion.