• Korean Journal of Environment and Ecology
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• v.28 no.2
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• pp.128-141
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• 2014

This study established a plan to establish the roadside green for enhancing the urban green network and enhancing of urban greenery in Songpa-gu. As for the present conditions of the streets, that of the parks, the green axes, sidewalk in Songpa-gu were analyzed. This study derived 19 parks by the roadside and 13 lines to connect green axes. The result of roadside greenery status were selected 56,546m lines by natural green space and constructed green space. The result of sidewalks width were selected 8,600m lines that sidewalks width more than 5m for enhancing urban green network in Songpa-gu. For enhancing the urban green network lines were selected: Olympic Expressway, Songpa-daero, Nambusunhwan-no and Wiryeseong-gil. To improve the street planting strips, two plans were suggested: to improve the green structures of the street planting strips mainly with shrubs and to effectively create street planting strips through the green spaces along the streets. A plan to promote the amount of planting street trees in Songpa-gu analyzed the streets. Complements the understory layer sections were the highest the entire length of 34,206 m of 63.6% in strengthening for network streets. Greenspace network streets were calculated for planting of volume by promotion plan. Planting volume increased 4,708 trees before expand planting plan, so the total tree was considered 9,518 trees.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.422-427
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• 2005

In this paper, Doherty amplifier is designed by the need of improving the linearity and efficiency of wireless network and repeater for WCDMA. It is designed to maintain the high linearity and efficiency at the low efficiency period of the power amplifier after analyzing Doherty technique using the active load-pull in condition of the high efficiency power amplifier implementation according to the variation of input power. CW 1-tone experimental results at the WCDMA frequency 2.11$\~$2.17 CHz shows that Doherty amplifier, which achieves pore. add efficiency(PAE) 50$\%$ at 6dB back off the point from maximum output power 52.3dBm, obtains higher efficiency of 13.3$\%$ than class AB. finding optimum bias point after adjusted gate voltage, Doherty amplifier shows that IMD3 improves 4dB.

• Journal of Advanced Navigation Technology
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• v.21 no.2
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• pp.206-211
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• 2017

Recently computing devices by connecting to a network, grid computing, the next generation of digital neural networks that provide maximum service will connect all of the computer such as a PC or server, PDA into one giant network makes the virtual machine. Therefore, we propose the grid computing implementation model to be applied to meteorological business field as follows. First, grid computing will be used for tasks such as the development of numerical models below the mid-scale or test operations, and the final backup of the weather supercomputer. Second, the resources that will constitute grid computing are limited to business PCs and Linux servers operated by the central government considering operational efficiency. Third, the network is restricted to the LAN section, which suggests the implementation of high performance computing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.205-213
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• 2012

In this paper, we propose a new channel hopping scheme based on IEEE 802.11h as a good countermeasure against jamming attacks in IEEE 802.11 wireless networks. 802.11h Dynamic Frequency Selection (DFS) is a mechanism which enables hopping to a best channel with full channel measurement, not a randomly chosen channel, when the current link quality degradation occurs due to interferers such as military radars. However, under jammer attacks, this needs a time for full channel measurement before a new channel hopping and due to link disconnection during the time network performance degradation is inevitable. In contrast, our proposed schemes make an immediate response right after a jammer detection since every device is aware of next hopping channel in advance. To do this, a next hopping channel is announced by Beacon frames and the channel is selected by full channel measurement within Beacon intervals. Simulation results show that proposed scheme minimizes throughput degradation and keeps the advantages of DFS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.180-186
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• 2017

In this paper we propose a traffic aware Demand Wakeup MAC(TADW-MAC) protocol, in which low data delay and high throughput can be achieved, for wireless sensor networks. With the TADW-MAC protocol, the problem of the DW-MAC protocol, which schedules only one packet to deliver during the Sleep period in a multi-hop transmission is resolved. DW-MAC is not adequate for the applications such as object tracking and fire detection, in which busty data should be transmitted in a limited time when an event occurs [6-8]. When an event occurs, duty cycle can be adjusted in the TADW-MAC protocol to get less energy consumption and low latency. The duty cycle mechanism has been widely used to save energy consumption of sensor node due to idle listening in wireless sensor networks. But additional delay in packet transmission may be increased in the mechanism. Our simulation results show that TADW-MAC outperforms RMAC and DW-MAC in terms of energy efficiency while achieving low latency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.8
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• pp.667-673
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• 2014

In a smart shipyard area, it is possible to integrate a variety of ship modules from separate sites into a final ship construction by using mobile applications. In this paper, we proposed the LTE femtocell network configuration which is applicable to sub shipyard, the traffic exchange method with shipyard headquarter and offload method to separate the general traffic. We defined the mode change in a femtocell gateway for supporting offload for general traffic between the main server in shipyard headquarter and sub shipyard, the offload data managements and message definition. We check the transmitted/received message flow in the wireless link, and consider the performance of the proposed method using state the transition diagram. It is expected that our results can improve the productivity within a smart shipyard by mobile communications and LTE femtocell network.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.127-134
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• 2012

Four river project in the South Korea contributes to solve flood damages and water shortages. Also, it has purpose for creating water ecosystem and improving the level of people' cultural leisure and quality of life through inducing water quality improvement and river restoration. It is necessary to monitor a variety of observing data in river areas among dozens to hundreds of kilometer for safe river administration. The 20th construction area of the four river project is located on Hapcheon areas, where wireless mesh network was installed to manage the basin. In the process of network construction, the characteristic of surrounding areas is considered about embodying secure service by investing the least expense. Besides, transmission environment analysis is performed such as LOS tests and reception level analysis, and transmission speed measurement to create safe service. Reception level in all places is confirmed among -55 dBm ~ -70 dBm, and data transmission speed proves more than 20 Mbps.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.341-349
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• 2017

CCN proposes that intermediate network nodes on a network path for a transmitted data-packet cache the data-packet. If the nodes receive request packets for the cached data, the nodes can directly respond to the request-packets using the cached data. Since a request-packet can be responded by one of the intermediate nodes on a path of the request-packet, both faster response time and decreased data transmission amount are expected comparing to the existing host centric networking. However, CCN is vulnerable against forgery attacks because data-packet receivers cannot identify a data provider. Hence, a data authentication scheme is essentially needed to make CCN more secure. But such a data authentication process is one of the main causes of CCN-based service delays. This paper first analyzes the problems of a CCN data authentication scheme, then proposes an improved authentication operation scheme for efficiently authenticating data, and finally evaluates its performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.955-963
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• 2009

In this paper, we propose a medium access control(MAC) protocol for reducing the energy efficiency and for improving the transmission efficiency in underwater acoustic sensor networks. In underwater environment, the transmission delay is longer and bandwidth is smaller than terrestrial environment. Considering these points, we propose a new MAC protocol to enhance throughput and to manage efficiently the energy of nodes. The proposed protocol operates as a channel reservation scheme to decrease data collisions, and uses a mechanism to control the hidden node problem and the exposed node problem occurred in ad hoc networks. The proposed protocol consists of the slotted based transmission frame and reduces data collisions between nodes by putting separately the reservation period in the transmission frame. In addition, it is able to solve the hidden node problem and the exposed node problem by reservation information between nodes. We carry out the simulation to evaluate the proposed protocol in terms of the average energy consumption, the ratio of collision, throughput, and the average transmission delay, and compare the proposed protocol to a traditional MAC protocol in the underwater environment. The simulation results show that the proposed protocol outperforms the traditional protocol under a various of network parameters.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.67-73
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• 2009

This paper proposes a new fast vertical handover mechanism to optimize and enhance the existing fast vertical handover HMIPv6(FV-HMIP) mechanism in heterogeneous wireless access networks. The proposed mechanism ad opts the IEEE 802.21 Media Independent Handover Function(MIHF), and thus is called the "MFV-HMIP". The Media Independent Handover Service (MIIS) in the IEEE 802.21 MIHF is extended by including new L3 inform ation to provide domain prefixes of heterogeneous neighbouring mobility anchor points(MAPs). This can eliminate the heterogeneous neighbouring MAP discovery phase in the existing FV-HMIP. Thus, the proposed MFV-HMIP can reduce the signalling traffic over wireless link and increase the possibility of predictive mode operation. Therefore, the proposed MFV-HMIP mechanism can be superior to the existing FV-HMIP mechanism for wireless resource efficiency, handover latency, and packet loss. Through analytic performance evaluations and computer si mulations, the proposed mechanism can be shown to optimize and enhance the existing mechanism.