• Smart Media Journal
• /
• v.8 no.2
• /
• pp.21-28
• /
• 2019

Recent research on energy harvesting wireless sensor networks focuses on the development of techniques to solve the limited energy resource problem and to extend the whole network life efficiently. Energy harvesting technology can increase the lifetime of a network, but data transmission becomes unavailable when it harvests energy from radio frequency, resulting longer network delay with respect to the increased time in energy harvesting. Therefore, building energy harvesting wireless sensor network should consider the possible network delay as well as the network lifetime problem. In this paper, we propose a new MAC protocol that minimizes end-to-end network delay by adjusting the data transmission time for a packet based on estimating the energy for data transmission along with the amount of traffic flowing into the network and harvested energy. For this goal, it engineers an energy management mechanism that adjusts the sleep time of the network by measuring energy harvesting time. In addition, with simulation results it shows that the proposed MAC protocol improves the performance in terms of energy consumption and end-to-end delay, compared to the existing MAC protocols.

• Proceedings of the Korea Contents Association Conference
• /
• 2009.05a
• /
• pp.306-311
• /
• 2009

We initially obtained human diseases-related proteins dataset from the OMIM and the SWISS PROT and then constructed disease-related protein-protein interaction network. The protein network contains 40 hub proteins such as CALM1, ACTB and ABL2. The protein network can be derived the map of the relationship between different disease proteins, denoted disease interaction network. We demonstrate that the associations between diseases are directly correlated to their underlying protein-protein interaction networks. From constructed the disease-protein bipartite network, we derived 38 diseasomal proteins, including APP, ABL1 and STAT1. We previously demonstrated that hub proteins in the network tend to be diseasomal proteins in the disease-related protein sub-networks. However, we found that 18% hubs are only diseasomal proteins in the whole disease network. At this point, we could not elucidate difference in the hub-diseasomal proteins tendency between sub0network and whole network. In spite of we still have unsolved problems, our results elucidate that the discovery of protein interaction networks assigned by diseases will provide insight into the underlying molecular mechanisms and biological processes in complex human disease system.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.1
• /
• pp.47-58
• /
• 2018

The heterogeneous cellular network (HCN) is most significant as a key technology for future fifth generation (5G) wireless networks. The heterogeneous network considered consists of randomly macrocell base stations (MBSs) overlaid with femtocell base stations (BSs). The stochastic geometry has been shown to be a very powerful tool to model, analyze, and design networks with random topologies such as wireless ad hoc, sensor networks, and multi- tier cellular networks. The HCNs can be energy-efficiently designed by deploying various BSs belonging to different networks, which has drawn significant attention to one of the technologies for future 5G wireless networks. In this paper, we propose switching off/on systems enabling the BSs in the cellular networks to efficiently consume the power by introducing active/sleep modes, which is able to reduce the interference and power consumption in the MBSs and FBSs on an individual basis as well as improve the energy efficiency of the cellular networks. We formulate the minimization of the power onsumption for the MBSs and FBSs as well as an optimization problem to maximize the energy efficiency subject to throughput outage constraints, which can be solved the Karush Kuhn Tucker (KKT) conditions according to the femto tier BS density. We also formulate and compare the coverage probability and the energy efficiency in HCNs scenarios with and without coordinated multi-point (CoMP) to avoid coverage holes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.3
• /
• pp.497-505
• /
• 2015

Existing Wi-Fi networks require users to follow network settings of the AP (Access Point), resulting in inconveniences for users, and the password of the AP is shared by all users connected to the AP, causing security information leaks as time goes by. We propose, in this work, a personalized secure Wi-Fi network, in which each user is assigned her own virtual Wi-Fi network. One virtual Wi-Fi per user makes the user-centric network configuration possible. A user sets a pair of her own SSID and password on her device a priori, and the AP publishes its public key in a suitable way. The AP also maintains an open Wi-Fi channel, to which users can connect anytime. On user's request, the user device sends a connection request message containing a pair of SSID and password encrypted with the AP's public key. Receiving the connection request message, the AP instantiates a new virtual AP secured with the pair of SSID and password, which is dedicated to that single user device. This virtual network is securer because the password is not shared among users. It is more convenient because the network adapts itself to the user device. Experiments show that these advantages are obtained with negligible degradation in the throughput performance.

• Korea journal of population studies
• /
• v.31 no.3
• /
• pp.107-130
• /
• 2008

The study of Korean diaspora has focused on migration, adaptation, and identity of overseas Koreans in China, the CIS, Japan, and the United States. However, the contemporary concept of a diaspora is a way of understanding migration, cultural difference, identity politics, and so on. Thus, this more broadly defined diaspora is used to mean a dispersion of people of a common national origin or of common beliefs living in exile. As of 2007, it is estimated that there are about 7 million Koreans living in 170 countries outside the Korean peninsula. Some have left Korea involuntarily and some others voluntarily. But most of them actively try to maintain their identity and culture as Koreans. With the large number of overseas Koreans, there has recently been the recognition of the importance of networking among overseas Koreans in the 21st century. The purpose of this paper is to emphasize the necessity of Korean Global Network of overseas Koreans. In doing so, this paper reviewed the case of Jewish and Chinese network. Then, this paper indicates the problems in the networking of overseas Koreans and suggests the policy implications for Korean Global Network. Above all, there should be changes in the government's policy towards overseas Koreans in the direction of organizing networks of overseas Koreans to coexist with the mother country. The government should adopt a policy to restore trust in overseas Koreans. It should take a pragmatic approach to the mutual interests in the socioeconomic relations instead of taking a political approach to overseas Koreans.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.12
• /
• pp.529-538
• /
• 2002

Conventional method to reduce the handoff call blocking probability(PBH) in mobile communication system is to reserve a predetermined number of channels only for handoff calls. To determine the number of reserved channels, an optimization problem, which is generally computationally heavily involved, must be solved. In this Paper, we propose a call admission control (CAC) scheme that can be used to reduce the PBH without reserving channels in advance. For this, we define a new measure, gain, which depends on the state of the system upon the arrival of a new call. The proposed CAC decision rule relies on the gain computed when a new call arrives. SRN, an extended stochastic Petri nets, provides compact modeling facilities for system analysis can be calculated performance index by appropriate reward to the model. In this Paper, we develop SRN models which can perform the CAC with gain. The SRN models are 2 level hierarchical models. The upper layer models are the structure state model representing the CAC and channel allocation methods considering QoS with multimedia traffic The lower layer model Is to compute the gain under the state of the upper layer models.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.5A
• /
• pp.473-484
• /
• 2011

In this paper, we analyze and propose the Joint Call Admission Control(JCAC) scheme to combine network selection scheme and radio resource reservation based Call Admission Control(CAC) in LTE-WLAN heterogeneous networks. First, We propose the JCAC system that uses network decision rate to select a network for terminal and radio resource reservation scheme in overlaying LTE-WLAN network environment. And we analyze the performance of a proposed system using markov chain model. The performance is presented in terms of the new call blocking probability, handoff call dropping probability, and channel utilization of each network. As a performance result of the our research, the system using JCAC is better than the system using non-JCAC. We found a suitable resource reservation rate that is 10% in the system using JCAC. Our work may be useful as a guideline of resource reservation rate to introduce JCAC system using resource reservation scheme in overlaying LTE-WLAN network environment.

• Journal of Korea Multimedia Society
• /
• v.15 no.8
• /
• pp.1038-1047
• /
• 2012

The SIP(Session Initation Protocol) is an application layer protocol that is used to establish, release, and change the call session of the IP telephony. In the SIP signalling networks, when the number of the UA(User Agent) requested the call session increase, the number of messages to be processed by SIP proxy server increase. It often will be caused the overload of the SIP proxy server. In this paper, we proposed the overload control method with a normal queue and a delay queue in the SIP proxy server. When it is estimated the overload of the server by the excess of the high threshold in the normal queue, new INVITE messages will be put into the delay queue to reduce the load of the server. It results in some delay of the call session from the INVITE message. Subsequently when the number of messages in the normal queue is reduced below the low threshold, the INVITE messages in the delay queue is processed. The simulation results showed that the number of the retransmission messages by our proposed method was 45% less than the one by the method with single queue. The results also showed that the average call success rate by the proposed method was 2% higher than the one by the method with single queue.

• Proceedings of the Korean Information Science Society Conference
• /
• 2004.10b
• /
• pp.268-270
• /
• 2004

네트워크가 보편화되면서 어떠한 정보의 교환도 시간과 장소에 상관없이 가능하게 되었다. 자체 실험실에서 실험한 값을 포함하여 분산된 다양한 소스로부터 많은 실험 값의 정보를 통합하는 즉, 멀티 소스 데이터에 대한 통합 규칙을 만들 수 있다면 다양하고 유용한 정보를 얻을 수 있을 것이다. 또한 통합된 규칙을 통해서 새로운 안목으로 실험을 진행할 수도 있으며, 미처 생각하지 못했던 관련 지식을 습득할 수도 있을 것이다. 본 논문에서는 이러한 분산된 데이터를 통합하여 멀티 소스 데이터들 간의 통합 규칙을 만들고 이의 분석 기반이 되도록 하는 방법에 대해 소개한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 2005.11a
• /
• pp.1003-1005
• /
• 2005

클러스터 시스템의 성능과 관련되어 중요성이 강조되는 분야로 SAN(System Area Network)을 이야기할 수 있다. 특히 infiniband 제품의 출시는 이 분야에 대한 관심을 더욱 집중시키는 계기가 되었다. 이에 본 논문에서는 Infiniband가 보여주는 단순한 네트워크적인 특징 이외에 응용 프로그램의 성능에 어떠한 영향을 미치는가에 대하여 실험하고 분석하였다.