• Journal of KIISE:Databases
• /
• v.32 no.3
• /
• pp.315-325
• /
• 2005

In mobile computing environments, a mobile host caches the data items to use the bandwidth efficiently and improve the response time of transactions. If the data items cached in mobile host are updated in the server, the server broadcasts an invalidation report for maintaining the cache consistency of mobile hosts. However, this method has a problem that the response time of mobile transactions can be long since their commit decision is delayed until receiving the invalidation report from the server In this paper, we propose the USR-MT method for improving the response time of mobile transactions. As the UGR-MT method can make a commit decision by using the data group information before receiving the invalidation report, the response time of mobile transactions can be improved. Also our method can improve the cache's efficiency since it prevents all the contents of a cache from being invalidated in the case that the disconnection of a mobile host is longer than the broadcast period of invalidation report.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.3
• /
• pp.258-267
• /
• 2013

Recently, Proxy Mobile IPv6(PMIPv6) networks have been drawing attention as the mobility management protocol that uses limited wireless resources effectively. And the multicast, which is a core technology of the Internet broadcast system such as mobile IPTV, has been widely discussed mainly based on PMIPv6 network. However, PMIPv6-based multicast cannot support the global mobility directly between different PMIPv6 domains because PMIPv6 is basically designed for local mobility in single PMIPv6 domain. Moreover, PMIPv6-based multicast causes the disconnection of services because it does not solve the packet loss problem during binding and group joining procedure. In this paper, we propose a global mobility scheme that supports the seamless multicast service in PMIPv6 networks. The proposed scheme supports the global mobility due to the addition of extra signalling messages between LMAs. Also, it achieves low latency because it performs fast binding and group joining procedure. We present the simulation results which show that the proposed scheme achieves the global mobility with low latency through the NS-2 simulation.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.7
• /
• pp.1694-1705
• /
• 1997

In the future mobile computing environment, it will be generalized that a mobile host with portable Laptop of Palmtop accesses to database through wireless communication channel. For solving the problems which are caused from low bandwidth of wireless communication, mobile hosts cache the datum used frequently on them. Thus the mobile hosts must always retain the cache consistency for the correctness of the cached datum. the cache consistency is mainly affected from the unrestricted host mobility and the disconnection of the communication between mobile hosts and mobile support station. In this situation, the strategy to retain efficiently cache consistency is required. In this paper, we propose a strategy using updatable message for retaining the cache consistency, in the mobile computing environment, with replicated database supporting 2 phase commit protocol. This strategy makes use of a updatable message to resolve the cache consistency problem, since mobile host crosses the boundary of cell. In using of this updatable, it find out and cache only the update data of missing invalidation message. As a result, the proposed strategy utilizes network bandwidth efficiently because it is not need to delete all the cached datum with any datum change.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.1
• /
• pp.233-241
• /
• 2013

One fundamental issue in ad hoc networks is the alternative node election problem, which reflects how well a sensor network is monitored or tracked by sensors. In this paper, we proposed EEAP(Energy-Efficient Alternative Paths). This is a method of selecting an alternative node for path routing management. When some node disconnection on the path routing, using pre-selected backup node provides immediately recover the path recovery. When selecting an alternative node of Step-Parents head node on the path management, the node's energy level and distance information are cared in context-awareness. This is not only increased the system's capacity cost effectively, but also reduce transmission power entire nodes consume energy. As a result, each node could efficiently management and improves the life time for mobile host and extends system coverage.

• Industry Promotion Research
• /
• v.9 no.1
• /
• pp.103-111
• /
• 2024

In this study, the problem of child care gaps has arisen due to the expansion of women's entry into the workforce and the increase in working couples, and the care cliff phenomenon after children enter elementary school has been identified as one of the causes of women's career disconnection and low birth rates, and child care services have been initiated to solve care problems and balance work and family. The importance of childcare services to the safety and well-being of children has been highlighted by the restrictions on school attendance and the absence of caregivers during the COVID-19 pandemic. The government has been making policy efforts to reduce the gap in child care, but problems with the effectiveness and efficiency of the child care system have arisen due to unstable target selection and delivery systems by ministries and projects in the implementation of child care services. Therefore, this study examines the child care services implemented by each ministry to reduce the blind spots of after-school care services in the community and prepare efficient operation plans for various delivery systems, and seeks directions for the development of child care services.

• Korean Chemical Engineering Research
• /
• v.60 no.1
• /
• pp.86-92
• /
• 2022

Recently, the bio-healthcare market is enlarging worldwide due to various reasons such as the COVID-19 pandemic. Among them, biometric measurement and analysis technology are expected to bring about future technological innovation and socio-economic ripple effect. Existing systems require a large-capacity battery to drive signal processing, wireless transmission part, and an operating system in the process. However, due to the limitation of the battery capacity, it causes a spatio-temporal limitation on the use of the device. This limitation can act as a cause for the disconnection of data required for the user's health care monitoring, so it is one of the major obstacles of the health care device. In this study, we report the concept of a standalone healthcare monitoring module, which is based on both triboelectric effects and electromagnetic effects, by converting biomechanical energy into suitable electric energy. The proposed system can be operated independently without an external power source. In particular, the wireless foot pressure measurement monitoring system, which is rationally designed triboelectric sensor (TES), can recognize the user's walking habits through foot pressure measurement. By applying the triboelectric effects to the contact-separation behavior that occurs during walking, an effective foot pressure sensor was made, the performance of the sensor was verified through an electrical output signal according to the pressure, and its dynamic behavior is measured through a signal processing circuit using a capacitor. In addition, the biomechanical energy dissipated during walking is harvested as electrical energy by using the electromagnetic induction effect to be used as a power source for wireless transmission and signal processing. Therefore, the proposed system has a great potential to reduce the inconvenience of charging caused by limited battery capacity and to overcome the problem of data disconnection.

• Journal of KIISE
• /
• v.42 no.10
• /
• pp.1254-1267
• /
• 2015

Recently, excessive installations of APs have caused WLAN interference, and many techniques have been suggested to solve this problem. The AP aggregation technique serves to reduce active APs by moving station connections to a certain AP. Since this technique forcibly moves station connections, the transmission performance of some stations may deteriorate. The AP transmit power control technique may cause station disconnection or deterioration of transmission performance when power is reduced under a certain level. The combination of these two techniques can reduce interference through AP aggregation and narrow the range of interferences further through detailed power adjustment. However, simply combining these techniques may decrease the probability of power adjustment after aggregation and increase station disconnections upon power control. As a result, improvement in performance may be insignificant. Hence, this study suggests a scheme to combine the AP aggregation and the AP transmit power control techniques in OpenFlow-based WLAN to ameliorate the disadvantages of each technique and to reduce interferences efficiently by performing aggregation for the purpose of increasing the probability of adjusting transmission power. Simulations reveal that the average transmission delay of the suggested scheme is reduced by as much as 12.8% compared to the aggregation scheme and by as much as 18.1% compared to the power control scheme. The packet loss rate due to interference is reduced by as much as 24.9% compared to the aggregation scheme and by as much as 46.7% compared to the power control scheme. In addition, the aggregation scheme and the power control scheme decrease the throughput of several stations as a side effect, but our scheme increases the total data throughput without decreasing the throughput of each station.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.8
• /
• pp.304-314
• /
• 2020

This study examined the experiences of the suicide crisis and recovery process by elderly women living alone to identify the essential meaning and components of life as a life to live again. In addition, the recovery of the research participants, as well as the phenomenon of such changes in thought and life, were examined. The results of this study were as follows. Data analysis yielded four components, eight sub-components, and 16 semantic unit reductions. There were four components of suicide attempts and recovery experiences of elderly women. They were "disconnection and disqualification," "repeated hardships," "road of prosperity in trouble," and "generous tolerance." The essential topics of these components have emerged not as individual but as holistic and contextually connectable topics. Finally, to summarize the results, the essential semantic structure of the suicide attempt and recovery experience of elderly women living alone is a result of a dysfunctional social structure and environment, which has placed pressure on the life of research participants. As an alternative method to overcome, they tried to solve the problem through the extreme practice of suicide attempts, but positive energy to live again due to emotional recovery factors recognized through suicide failures have made it possible to cope with the difficult reality.

• Journal of KIISE:Computing Practices and Letters
• /
• v.8 no.5
• /
• pp.583-589
• /
• 2002

The Internet is absolutely contributed to information telecommunication revolution nowadays. Realizing local network at the various type of buildings such as a company and a university, ethernet is used for subnet and FDDI, ATM are used for backbone mainly in order to get internet services. Processing TCP/IP protocol suite and analyzing the protocol exactly is essential to detecting the problem occurring in the network and developing communication equipment. This paper presents implementation of ethernet LAN protocol analyser which monitors and simulates ICP/IP protocol suite carrying the Internet and non-Internet protocol such as Netware and NetBIOS. MS window98 and visual C are used for development environment and application program operates on the NDIS firmware. The performance analysis on the proposed system is carried out as monitoring and simulating the traffic over LAN of a university. In the result of monitoring the system, the processing time of a packet captured over the LAN is about 1.5ms. In case of simulating the system, the processing time to be taken carrying out TCP connection and disconnection once is packet is about 8.6ms. The performance analysis of monitoring and simulation results satisfies with 10 Mbps ethernet LAN environment.

• The KIPS Transactions:PartC
• /
• v.8C no.6
• /
• pp.775-782
• /
• 2001

Recently the use of Linux OS is increasing to tremendous figures. But due to the fact that Linux is distributed on an open-source policy, the need of security is an upcoming question which leads to widespread development of security on a Linux based environment. Cryptography, however, can cause various problems because of difficulty of key management. A lot of researchers have been concentrating on the key recovery technique to eliminate the reverse effect of using these kinds of security and to promote positive aspects of using it. In this thesis I am suggesting an mechanism based on the key recovery technique, as a method to save time in recovery and resetting a disconnection between two end-users through IPSec (IP Security) protocols in a VPN (Virtual Private Network) environment. The main idea of the newly suggested mechanism, KRFSH (Key Recovery Field Storage Header), is to store the information of the session in advance for the case of losing the session information essential to establish a tunnel connection between a SG and a host in the VPN environment, and so if necessary to use the pre-stored information for recovery. This mechanism is loaded on the IPSec based FreeS/WAN program (Linux environment), and so the VPN problem mentioned above is resolved.