• The KIPS Transactions:PartB
• /
• v.12B no.2 s.98
• /
• pp.137-142
• /
• 2005

Since wireless communication cost is relatively expensive, the mobile games using cellular phones or PDAs are mostly played after being downloaded unlike more updated types of phone-to-phone or online games. In particular, the upbringing games, in which garners foster virtual companion animals or vegetables as their avata, have been spotlighted. It is essential to supply variety of items for upbringing avatas. However, due to diverse tastes for avatas and limited storage of mobile terminals, game manias must download their desired items from homepages. In addition, game developers must inform users through SMS messages whenever a new item is created. To do so, they must link WEB server and WAP server to Call Back URL or ARS. This paper proposed a linkage method suitable for JAVA-based mobile phone operating system. The proposed method will consequently increase life cycle of a game and reinforce profitability.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.14 no.8
• /
• pp.1836-1842
• /
• 2010

Sensor network, which is technology to realize the ubiquitous environment, recently, could apply to the field of Mechanic & electronic Security System, Energy management system, Environment monitoring system, Home automation and health care application. However, feature of wireless networking of sensor network is vulnerable to eavesdropping and falsification about message. Presently, PKC(public key cryptography) technique using ECC(elliptic curve cryptography) is used to build up the secure networking over sensor network. ECC is more suitable to sensor having restricted performance than RSA, because it offers equal strength using small size of key. But, for high computation cost, ECC needs to enhance the performance to implement over sensor. In this paper, we propose the optimizing technique for multiplication, core operation in ECC, to accelerate the speed of ECC.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.920-925
• /
• 2010

A home network system is made up of home devices and wire and wireless network can not only be the subject of cyber attack from a variety factors of threatening, but also have security weakness in cases of hacking, vicious code, worm virus, DoS attack, tapping of communication network, and more. As a result, a variety of problems such as abuse of private life, and exposure and stealing of personal information arose. Therefore, the necessity for a security protocol to protect user asset and personal information within a home network is gradually increasing. Thus, this dissertation designs and suggests a home network security protocol using user authentication and approach-control technology to prevent the threat by unauthorized users towards personal information and user asset in advance by providing the gradual authority to corresponding devices based on authorized information, after authorizing the users with a Public Key Certificate.

• Journal of KIISE:Computer Systems and Theory
• /
• v.26 no.10
• /
• pp.1206-1216
• /
• 1999

이동 호스트란 시간과 공간의 제약 없이 필요한 기능을 수행하고, 또한 원하는 정보에 접근할 수 있는 휴대용 컴퓨터를 일컫는다. 이동 컴퓨팅 환경이란 이러한 이동 호스트들을 지원할 수 있도록 구성된 분산 환경이다. 따라서 이동 컴퓨팅 환경에서의 분산 알고리즘은 정적 호스트만을 고려한 기존의 분산 환경에서와는 다르게 이동 호스트의 여러 가지 특성들을 고려하여 제안되어야 한다. 즉, 이동 컴퓨팅 환경의 도래로 인하여 이동성과 휴대성, 그리고 무선 통신과 같은 특성들을 고려한 새로운 분산 상호 배제 알고리즘이 필요하다. 이제까지 이동 컴퓨팅 환경에서의 상호 배제 알고리즘은 토큰 링 구조에 기반을 두고 설계되었다. 토큰 링 구조는 이동 호스트들의 위치를 유지하기 위하여 높은 비용을 필요로 하는 단점을 가지고 있다. 본 논문에서는 균형 높이 트리(height-balanced tree)라는 새로운 모형을 제안함으로써 정적 분산 환경과 이동 분산 환경이 혼합된 환경에서 상호 배제 비용을 감소시킬 수 있는 새로운 알고리즘을 제안하며, 각 경우에 있어서의 비용을 산출하고 평가한다.Abstract The mobile host is a potable computer that carries out necessary functions and has the ability to access desirable informations without any constraints in time and space. Mobile computing environment is a distributed environment that is organized to support such mobile hosts. In that environment, distributed algorithms of which environment not only with static hosts but with mobile host's several properties should be proposed. With the emergence of mobile computing environments, a new distributed mutual exclusion method should be required to consider properties mobile computing system such as mobility, portability, and wireless communication. Until now, distributed mutual exclusion methods for mobile computing environments are designed based on a token ring structure, which have the drawbacks of requiring high costs in order to locate mobile hosts. In this paper, we propose a distributed mutual exclusion method that can reduce such costs by structuring the entire system as a height-balanced tree for static distributed networks and for networks with mobile hosts. We evaluated the operation costs in each case.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.11
• /
• pp.2576-2583
• /
• 2015

In a full-duplex (FD) wireless cellular network, uplink (UL) users induce the severe inter-user interference to downlink (DL) users. Therefore, a user scheduling that makes a pair of DL user and UL user to use the same radio resource simultaneously influences the system performances significantly. In this paper, we first formulate an optimization problem for user scheduling to minimize the occurrence of outage, aiming to guarantee the quality of service of users, and then we propose a suboptimal user scheduling algorithm with low complexity. The proposed scheduling algorithm is designed in a way where the DL user with a worse signal quality has a higher priority to choose its UL user that causes less interference. Simulation results show that the FD system using the proposed user scheduling algorithm achieves the optimal performance and significantly decreases the outage probability compared with the conventional half-duplex cellular system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.10B
• /
• pp.899-915
• /
• 2003

Delivering rich and continuous media contents robustly over a wide range of network conditions of the wired/wireless Internet is a highly challenging task. To address this challenges, the continuous media applications at the edge of network has become more and more adaptive while the best-effort Internet is slowly progressing towards improved networking services. That is, the role of network adaptive media delivery, which dynamically links the quality demand of application contents to the underlying networking services, has become more crucial. In this paper, we will first review the required network adaptation functionalities seen from the application side: congestion control / rate control, error control, and synchronization / adaptive playout. Then, we start the coverage of networking support issues that helps the realization of network adaptive media streaming - from network support and protocol support toward consolidated support via middleware. Finally, we propose a dynamic network adaptation framework that efficiently leverages its awareness of both media application (including contents) and underlying networking support.

• Journal of Korean Society of Transportation
• /
• v.26 no.4
• /
• pp.123-133
• /
• 2008

Information collection systems and applications in a ubiquitous environment has emerged as a leading issue in transportation and logistics. A productive application example is a traffic information collection system based on probe vehicles and wireless communication technology. Estimation of hourly OD pairs using probe OD data is a possible target. Since probe OD data consists of sample OD pairs, which vary over time and space, computation of sample rates of OD pairs and expansion of sample OD pairs into static OD pairs is required. In this paper, the authors proposed a method to estimate sample OD data with probe data in Jeju City and expand those into static OD data. Mean absolute percentage difference (MAPD) error between observed traffic volume and assigned traffic volume was about 22.9%. After removing abnormal data, MAPD error improved to 17.6%. Development of static OD estimation methods using probe vehicle data in a real environment is considered the main contribution of this paper.

• Journal of Advanced Navigation Technology
• /
• v.14 no.6
• /
• pp.859-864
• /
• 2010

In the next generation system, a study on realization of Multi-Core system is in progress for applying it in multi service network. Therefore some mobile systems are expected to be appeared. These systems can support WiBro, WCDMA, CDMA, etc with single terminal. These systems have to support various FA using broadband frequency and hand over to other service network. Especially, in the telecommunication system composed of cell, the transmit power can be interference at adjacent system, has effect on system channel capacity and cell size. In this paper, we improve the unstable transmit power caused by unsettled system operation, propose the RF(Radio Frequency) Calibration method which can use the transmit power stably even during hand over between heterogeneous networks causing unstable power change. Also we used proposed method and analysed used electricity of system during hand over between heterogeneous networks.

• Journal of Advanced Navigation Technology
• /
• v.17 no.5
• /
• pp.484-490
• /
• 2013

With the rapid development of wireless communication at VHF and UHF bands, there is an increasing need for the reliable propagation prediction tools. Therefore, the different propagation models that have been developed in many countries as well as korea has been trying to secure a model suitable for their geographical area but then it is giving us a different result when we compared it to measured values. In this paper, based on the measurements of DTV broadcasting services in domestic urban area, analysis and comparison of ITU-R P.1546 and BCAST models provide errors between measured and predicted values, and some points for improving SMI system has been proposed. As a result, P.1546 model provides the valid predicted data similar to measured data, but BCAST model has some problems of large deviation and higher prediction to measured data. In future, these problems and diffractions due to high buildings need to be studied further.

• The Journal of the Korea Contents Association
• /
• v.9 no.9
• /
• pp.9-17
• /
• 2009

RFID (Radio Frequency Identification) is a next generation technology that will replace barcode. RFID can identify an object by reading ID inside a RFID tag using radio frequency. However, because a RFID tag replies its unique ID to the request of any reader through wireless communication, it is vulnerable to attacks on security or privacy through wiretapping or an illegal reader's request. The RFID authentication protocol has been studied actively in order to solve security and privacy problems, and is used also in tag search. Recently, as the number of tags is increasing in RFTD systems and the cost of data collection is also rising, the importance of effective tag search is increasing. This study proposed an efficient search method that solved through ta9 group the problem of large volume of database computation in Miyako Ohkubo's hash chain mechanism, which meets requirements for security and privacy protection. When we searched first the group of tags with access rate of 5 or higher in a database with 100,000 records, search time decreased by around 30%.