• Journal of Internet Computing and Services
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• v.12 no.2
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• pp.75-83
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• 2011

Wireless services and devices that use frequency increase more and more because of advancement of the industry. Therefore, the available spectrum band becomes increasingly insufficient. Cognitive Radio, which adaptively utilizes the vacant licensed spectrum band, is considered as an effective way to utilize the spectrum resource shortage. CR user should move from current allocated channel to vacant channel to avoid the interference to the primary user when the primary user appears in the current channel. In this case, CR system undergoes the break off time until handshake is completed. So, in order to guarantee the Quality of Service(QoS) of CR system, fast handshake method is required. In this paper, we propose the embedded control signal transmission technique to reduce the break off time. This method can transmit the control signals in data transmission period as well as the broadcasting period. Proposed method can improve the data throughput and decrease the break off time. Computer based simulation proves that our proposed scheme outperforms conventional one.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.77-83
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• 2013

Nowadays, the limitation of Lighting control and management skills is the excessive cost of equipments, the operational difficulties and wasting energy. To solve this problem is in need of communication and management S/W that is worked out complexly well as a information system of smart lighting energy, which is loaded wireless network facility. This paper made a study od the energy saving technology through energy monitoring and we developed LEIS(Lighting Energy Information Sysem) to converge this one. LEIS is monitoring and control lighting energy data that is collelcted from sensors by Zigbee mesh network and shows lighting use information by visualization to users. It is consists of lighting energy information data base based on LEM(Lighting Energy Metering) information and LEIS Web application, provide function scenario to manage energy optimization through LEIS.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.5
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• pp.87-91
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• 2019

WSN is a wirelessly configured network of sensor nodes with limited power such as batteries. If the sensor node's battery is exhausted, the node is no longer available. Therefore, if the network is to be used for a long time, energy consumption should be minimized. There are many Wireless Sensor Network Protocols to improve energy efficiency, including Cluster-based and chain-based Protocols. Cluster-based Protocols elect Cluster Heads and divide sensor field into Clusters. The Cluster Head collects the data in the Cluster and transmits it to the Base Station. In the case of nodes elected as Cluster Heads, there is a problem of energy consumption. The chain-based Protocol links sensor nodes in a chain and finally transmits all data to the Base Station. In this paper, we intend to increase the network lifetime by using a chain to reduce the energy consumption of the Cluster Head in the Cluster-based Protocol, LEACH Protocol.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1152-1160
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• 2004

OFDM technique was adopted as the standard of IEEE 802.1 la and it has been widely used for wireless LAN, European DVB/DAB system, Korean DMB system. In the standard of IEEE 802.11a the data packet is composed of two parts, preamble and data. Preamble is composed of short pilots and long pilots, which are used for synchronization and estimation of frequency offset and channel. We can also compensate phase noise effect in the transceiver by using above pilots. The phase noise is more complicate than frequency offset and seriously affects system performance. In this paper, we newly propose CPE and ICI simultaneous compensation method to compensate phase noise generated by transceiver oscillator and compare with previous studies. As results, phase noise effect can be significantly compensated by CPE cancellation method, PNS algorithm and our proposed CPE and ICI compensation method. Especially, the proposed CPE and ICI compensation method can achieve the best BER performance compared with original OFDM, CPE cancellation method and PNS algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.391-398
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• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.159-166
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• 2008

Recently, according to the rapid development of location positioning technology and wireless communications technology and increasement of usage of moving object data, many researches and developments on the real-time locating systems which provides real time service of moving object data stream are under proceeding. However, MO (Moving Object) DBMS used based system in the in these systems is the inefficient management of moving object data streams, and the existing DSMS (Data Stream Management System) has problems that spatio-temporal data are not handled efficiently. Therefore, in this thesis, we designed and implemented spatio-temporal DSMS for efficient real-time management of moving object data stream. This thesis implemented spatio-temporal DSMS based STREAM (STanford stREam dAta Manager) of Stanford University is supporting real-time management of moving object data stream and spatio-temproal query processing and filtering for reduce the input loading. Specifically, spatio-temporal operators of the spatio-temporal DSMS support standard interface of SQL form which extended "Simple Feature Specification for SQL" standard specifications presented by OGC for compatibility. Finally, implemented spatio-temporal DSMS in this thesis, proved the effectiveness of the system that as applied real-time monitoring areas that require real-time locating of object data stream DSMS.

• International journal of advanced smart convergence
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• v.6 no.1
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• pp.57-67
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• 2017

In this paper, propose an algorithm to improve network lifetime by equally consuming energy of LEACH - Mobile sensor nodes. LEACH is one of energy efficient protocols. However, we did not consider the mobility of nodes. Therefore, the transmission reception success rate of the moving data is reduced. LEACH-Mobile is a protocol that has improved the drawbacks of these LEACH. However, since LEACH-Mobile has a larger number of data packets and consumes more energy than LEACH, it has a disadvantage that the lifetime of the network is short. In order to improvement these disadvantage, Based on the average of the remaining energy of the node, cluster heads are elected with a number of nodes whose energies are larger than the average of the remaining energy from the member nodes. After that, by trying to increase the lifetime of the network by equalizing the remaining energy. In to confirm whether improve the lifetime of the network, In this paper, the number of nodes and the position of all nodes are varied for each specific round, the rest energy is equalized, and the algorithm which uniformly selected the cluster head is compared with LEACH.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.83-86
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• 2003

With the opening of digital broadcast services and development of wire/wireless Internet, the current multimedia broadcasting is provided for has various services. The user will be provided lots of various content through the various channel and media. Content provider and consumer want the various service using content with the better quality which is fit to user preference. For transmitting this content in the limited transmission channel capacity, it needs to transmit the highly compressed content which user wants. The content of 3D mesh model-based on MPEG-4 enables the various content service that provides the lower capacity and the better quality, and Targeting service enables just provide the contents that user more wants and likes. The adaption of Java application program and 3D program can provide the content service utilizing 3D mesh model, so content provider and consumer can share the more information about the content. This paper has presented the study on the targeting service using compression of 3D mesh model-based on MPEG-4 and the adaptation of Java application program using it

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.5
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• pp.183-189
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• 2009

Recently, PCS, PDA and mobile devices, such as the proliferation of spread, GPS (Global Positioning System) the use of, the rapid development of wireless network and a regular user even images, audio, video, multimedia data, such as increased use is for. In particular, video data among multimedia data, unlike the moving object, text or image data that contains information about the movements and changes in the space of time, depending on the kinds of changes that have sigongganjeok attributes. Spatial location of objects on the flow of time, changing according to the moving object (Moving Object) of the continuous movement trajectory of the meeting is called, from the user from the database that contains a given query trajectory and data trajectory similar to the finding of similar trajectory Search (Similar Sub-trajectory Retrieval) is called. To search for the trajectory, and these variations, and given the similar trajectory of the user query (Tolerance) in the search for a similar trajectory to approximate data matching (Approximate Matching) should be available. In addition, a large multimedia data from the database that you only want to be able to find a faster time-effective ways to search different from the existing research is required. To this end, in this paper effectively divided into a grid to search for the trajectory to the trajectory of moving objects, similar to the effective support of the search trajectory offers a new grid-based search techniques.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5A
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• pp.459-468
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• 2006

Current routing in sensor networks focuses on finding methods for energy-efficient route setup and reliable relaying of data from the sensors to the sink so that the lifetime of the network is maximized. The existing routing protocols do not have routing tables to determine a path when packets are transferred. A sensor network by a routing table increases a cost of maintaining and updating a path, because sensor nodes have characteristics to be mobile and constrained capacity and resources. This paper proposes a new routing algorithm by broadcasting a bitmap in order to reduce the number of messages transferred when routing paths are established. Each node has a routing table with a bitmap, which contains link information. A bitmap is formed two-dimensional array, which consists of each row and column represented with a bit. The node only updates its own bitmap if it receives a bitmap from another adjacent nodes after the broadcasting. There by, each node has a bitmap with partial links information not total links information on the network. The proposed routing algorithm reduces the number of messages for routing establishment at least 10% compared with the previous algorithms.