• Journal of Communications and Networks
• /
• v.17 no.4
• /
• pp.406-418
• /
• 2015

Cognitive radio networks (CRNs) have emerged as a promising solution to the problem of spectrum under utilization and artificial radio spectrum scarcity. The paradigm of dynamic spectrum access allows a secondary network comprising of secondary users (SUs) to coexist with a primary network comprising of licensed primary users (PUs) subject to the condition that SUs do not cause any interference to the primary network. Since it is necessary for SUs to avoid any interference to the primary network, PU activity precludes attempts of SUs to access the licensed spectrum and forces frequent channel switching for SUs. This dynamic nature of CRNs, coupled with the possibility that an SU may not share a common channel with all its neighbors, makes the task of multicast routing especially challenging. In this work, we have proposed a novel multipath on-demand multicast routing protocol for CRNs. The approach of multipath routing, although commonly used in unicast routing, has not been explored for multicasting earlier. Motivated by the fact that CRNs have highly dynamic conditions, whose parameters are often unknown, the multicast routing problem is modeled in the reinforcement learning based framework of learning automata. Simulation results demonstrate that the approach of multipath multicasting is feasible, with our proposed protocol showing a superior performance to a baseline state-of-the-art CRN multicasting protocol.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.2A
• /
• pp.179-187
• /
• 2011

Recently, cognitive radio attracts lots of interest to effectively utilize the limited spectral resource. In the previous researches, we proposed a method to enhance the system capacity of the overall network by using Selfish Symbiotic architecture and Non-selfish Symbiotic architecture. In this research, we further enhance the previous works to OFDM-based CR networks by using efficient subchannel allocation. The system performance is evaluated through intensive simulations with multiple primary users as well as a single primary user with different numbers of CR users.

• Journal of the Korean Solar Energy Society
• /
• v.22 no.4
• /
• pp.97-106
• /
• 2002

The purpose of this study is to analyze the life cycle cost of primary cooling system by systematic support cost. Life Cycle Cost(LCC) is the process of making an economic assessment of an item, area, system, or facility by considering all significant costs of ownership over an economic life, expressed in terms of equivalent costs. The essence of life cycle costing is the analysis of equivalent costs of various alternative proposals. In order to select economical primary cooling system in early heat source plan stages, the research investigates cost items and cost characteristics during project process phases such as planning/design, construction, maintenance /management, and demolition/sell phases. The study also analyze the life cycle cost by capacity leading to suggest the most economical primary cooling system by systematic support cost.

• Journal of Communications and Networks
• /
• v.18 no.3
• /
• pp.340-350
• /
• 2016

The performance of large-scale cognitive radio (CR) networks with secondary users sustained by opportunistically harvesting radio-frequency (RF) energy from nearby primary transmissions is investigated. Using an advanced RF energy harvester, a secondary user is assumed to be able to collect ambient primary RF energy as long as it lies inside the harvesting zone of an active primary transmitter (PT). A variable power (VP) transmission mode is proposed, and an energy-based opportunistic spectrum access (OSA) strategy is considered, under which a secondary transmitter (ST) is allowed to transmit only if its harvested energy is larger than a predefined transmission threshold and it is outside the guard zones of all active PTs. The transmission probability of the STs is derived. The outage probabilities and the throughputs of the primary and the secondary networks, respectively, are characterized. Compared with prior work, the throughput can be increased by as much as 29%. The energy-based OSA strategy can be generally applied to a non-CR setup, where distributed power beacons (PBs) are deployed to power coexisting wireless signal transmitters (WSTs) in a wireless powered sensor network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 1999.11a
• /
• pp.384-389
• /
• 1999

Most document consists of primary content and supporting material, such as footnotes, detailed explanations, and illustrations, and the related supporting materials are linked as hypertext on web document. However the content of hypertext links Is appeared in the new windows on present web browser. Then the user will leave the primary material, may lose the entire context, and must have some difficulties to return to the primary context when the interest disappears. Using the technique for fluid links, we can solve these problems easily. If the mouse is putted on the link, the related material is presented in between lines or at margin maintaining the context of primary material. In this paper, we introduce the various browsing techniques using fluid links, analyze the forms and the features, and then we propose the best way to implement inJava.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.9 no.4
• /
• pp.51-57
• /
• 2013

Research on calibration of array antenna has become a hot spot in the area of signal processing and it is necessary to obtain the phase mismatch of each antenna channel. This paper presents a new calibration method for an array antenna system. In order to calibrate the phase mismatch of each antenna channel, we used primary synchronization signal (PSS) which exists in LTE downlink frame. Primary synchronization signal (PSS) is based on a Zadoff-Chu sequence which has a good correlation characteristic. By using correlation calculation, we can extract primary synchronization signal (PSS). After extracting primary synchronization signal (PSS), we use it to calibrate and reduce the phase errors of each antenna channel. In order to verify the new array antenna calibration algorithm which is proposed in this paper, we have simulated the proposed algorithm by using MATLAB. The array antenna system consists of two antenna elements. The phase mismatch of first antenna and second antenna is calculated accurately by proposed algorithm in the experiment test. Theory analysis and MATLAB simulation results are shown to verify the calibration algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.12
• /
• pp.3081-3099
• /
• 2012

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.15 no.6
• /
• pp.2128-2147
• /
• 2021

Cognitive radio systems are being implemented recently to tackle spectrum underutilization problems and aid efficient data traffic. Spectrum sensing is the crucial step in cognitive applications in which cognitive user detects the presence of primary user (PU) in a particular channel thereby switching to another channel for continuous transmission. In cognitive radio systems, the capacity to precisely identify the primary user's signal is essential to secondary user so as to use idle licensed spectrum. Based on the inherent capability, a new spectrum sensing technique is proposed in this paper to identify all types of primary user signals in a cognitive radio condition. Hence, a spectrum sensing algorithm using improved convolutional neural network and long short-term memory (CNN-LSTM) is presented. The principle used in our approach is simulated annealing that discovers reasonable number of neurons for each layer of a completely associated deep neural network to tackle the streamlining issue. The probability of detection is considered as the determining parameter to find the efficiency of the proposed algorithm. Experiments are carried under different signal to noise ratio to indicate better performance of the proposed algorithm. The PU signal will have an associated modulation format and hence identifying the presence of a modulation format itself establishes the presence of PU signal.

• Journal of the Korean Society for Library and Information Science
• /
• v.53 no.2
• /
• pp.49-68
• /
• 2019

The curriculum in primary and secondary school is at the heart of the education. In education, a curriculum is broadly defined as the comprehensive plan consisting of educational goal and objectives, instructional content, materials, teaching and learning method. Many countries has national level curricula in primary and secondary education, such as the Korea. Korean national curriculum has been revised 10 times. Currently, '2015 revised curriculum' is applied in korea. On the other hand, the Korean library association developed called a 'Library and information life' curriculum for information literacy instruction in 2007. However, this curriculum is based on the '2007 revised national curriculum', so it differs from the system and contents structure of the '2015 revised national curriculum'. Since the primary and secondary school applying the '2015 revised national curriculum', 'Library and information life' curriculum should be revised. Therefore, this study suggests the direction of revising the 'Library and information life' curriculum after comparing and analyzing '2015 revised curriculum' and 'Library and information life' curriculum.

• Journal of The Korean Association of Information Education
• /
• v.18 no.2
• /
• pp.307-316
• /
• 2014

In this study, we analyzed he computer operating system curriculum in primary and middle schools and suggested the content framework for them through review of previous research. After surveying primary and middle school teachers, we developed the framework based on the spiral curriculum. Through these surveys, we were able to determine when and how students should be introduced to the as curriculum. The content framework focuses on two areas: understanding and practicing computer OS. Each area has 4 levels which are based on the students' grade. We suggested developing textbooks and materials about computer OS; establishing Information Science as a part of the primary school curriculum: and offering lectures about computer OS to student teachers at the National Universities of Education.