• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.1
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• pp.34-45
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• 2013

Due to its self-configuring nature, the tactical mobile ad hoc network is used for communications between tactical units and the command and control center (CCC) in battlefields, where communication infrastructure is not available. However, when a tactical unit moves far away from the CCC or there are geographical constraints, the data link between two communicating nodes can be broken, which results in an invalid data route from the tactical units to CCC. In order to address this problem, in this paper we propose a hierarchical connectivity maintenance scheme, namely ADLCoM (Autonomous Data Link Connectivity Maintenance). In ADLCoM, each tactical unit has one or more GW (gateway), which checks the status of data links between tactical units. If there is a possibility of link breakage, GWs request ground or aerial unmanned vehicles to become a relay for the data link. The simulation results, based on tactical scenarios, show that the proposed scheme can significantly improve the network performance with respect to data delivery ratio.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.3
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• pp.71-83
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• 2020

Resilience is the capacity to maintain essential services under a range of circumstances from normal to extreme. It is achieved through the ability of assets, networks, systems and management to anticipate, absorb and recover from disturbance. It requires adaptive capacity in respect of current and future risks and uncertainties as well as experience to date. The agricultural infrastructures with high resilience can not only reduce the size of the disaster relatively, but also minimize the loss by reducing the time required for recovery. This study aims to evaluate the most suitable drought countermeasures with the analysis of various resilience indices by predicting future agricultural water shortage under land use and climate change scenarios for agricultural areas in Jeju Island. The results showed that the permanent countermeasure is suitable than the temporary countermeasures as drought size and the cost required for recovery increase. Wide-area water supply system, which is a kind of water grid system, is identified as the most advantageous among countermeasures. It is recommended to evaluate the capability of agricultural infrastructure against drought with the various Resilience Indices for reliable assessment of long-term effect.

• Journal of KIISE:Information Networking
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• v.37 no.1
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• pp.35-41
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• 2010

Since the ad-hoc network allow nodes to communicate each other without infrastructure system and predefined configuration, it comes into the spotlight that is suitable to ubiquitous society. In ad-hoc network, route recovery mechanism is considered important. Normally route recovery is needed to solve the link failure problem because there is no route maintaining system like a router in ad-hoc networks. In this paper we propose BS-AODV(Bidirectional Searching-AODV) route recovery method. The proposed method is a local repair method that can be applied in all of the network area. Unlike a limited local repair method in AODV. the proposed method adopts the bidirectional searching method where the upstream/downstream nodes can send the route maintenance messages. Restricting the flooding of route request messages, the proposed scheme attempts to minimize the costs of local repair, the performance of the proposed scheme is evaluated through the simulations. In two scenarios which variate the node numbers and node speed, the comparison among the proposed scheme, AODV and AOMDV is shown in terms of the control traffic and data delivery ratio.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.391-399
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• 2018

V2X communication is a technology in which a vehicle exchanges information with various entities such as other vehicles, infrastructure, networks, pedestrians, etc. through a wired or wireless network. Recently, V2X communication technology has been steadily developed and recently it has played an important role in autonomous cooperation driving technology combined with autonomous vehicle technology. Autonomous vehicles can utilize the external information received via V2X communication to extend the recognition range of existing sensors and to support more safe and natural autonomous driving. In order to operate these autonomous cooperative vehicles on public roads, the security and reliability of autonomous V2X communication should be verified in advance. In this paper, we present test scenarios and test procedures of secure V2X communication for cooperative automated driving and present verification results.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.1
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• pp.1-10
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• 2007

An advantage of the mobile ad hoc network (MANET) is that mobile nodes can self-organize the network topology without the help of network infrastructure. However, for the perfect self-organization of the MANET, each mobile node needs to self-configure its address. Even though a mobile node configures a unique address during the booting time, its address may conflict with nodes in other MANETs since MANETs containing the same address can be merged. The address autoconfiguration protocol implemented in this work consists of the strong DAD (Duplicate Address Detection) and the weak DAD. A unique address of a node is assigned by the strong DAD during the booting time and the weak DAD is used to detect address conflict and resolve address conflict during the ad hoc routing. In this work, we have implemented address autoconfiguration in the IPv6-based MANET using AODV as the routing protocol. We describe how the IPv6 address autoconfiguration is implemented and verify our implementation by showing the test scenarios on our testbed.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.6
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• pp.358-370
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• 2007

Software simulations have been widely used for the design and application development of a wireless sensor network that is an infrastructure of ubiquitous computing. In this study, we develop a sensor network simulator that can verify the behavior of sensor network applications, estimate execution time and power consumption, and simulate a large-scale sensor network. To implement the simulator, we use an instruction-level parallel discrete-event simulation method. Instruction-level simulation uses executable images loaded into a real sensor board as workload, such that it results in the high degree of details. Parallel simulation makes simulation of a large-scale sensor network possible by distributing workload into multiple computers. The simulator can predict the amount of power consumption based on operating time of modules in a sensor node and counting the number of executed instructions by kind. Also it can simulate ubiquitous applications with various scenarios and debug programs. Instruction traces used as workload for simulations are executable images produced by the cross-compiler for ATmega128L microcontroller.

• Korean Journal of Remote Sensing
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• v.27 no.3
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• pp.339-351
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• 2011

This study investigates the potentials of satellite, ground measurement data, and geo-spatial information within an urban area for the mapping of the Urban Environmental Quality (UEQ) parameters. The UEQ indicates a complex and various parameters resulting from both human and natural factors, which are greenness, climate, air pollution, the urban infrastructure, and etc. Multi-spectral remote sensing data from the Landsat ETM and TM sensors for the mapping of air pollution by the Haze Optimized Transform (HOT) technique, Urban Heat Island (UHO using the emissivity-fusion method in Seoul from 2000 to 2006 in fine resolution (30m) were analyzed for the estimation of UEQ index. Although the UHI values are similar ($8.4^{\circ}C{\sim}9.1^{\circ}C$) during these years, the spatial coverage of "hot" surface temperature (> $24^{\circ}C$) significantly increased from 2000 to 2006 due to the rapid urban development. Furthermore, high correlations between vegetation index and land surface temperature were achieved with a correlation coefficients of 0.85 (2000), 0.81 (2001), 0.84 (2002), and 0.89 (2006), respectively. It was found that the proposed method was successfully analyzed spatial structure of the UEQ and the scenarios of the best and worst areas within the city were also identified. Based on the quantifiable fine resolution satellite image parameters, UEQ can promote the understanding of the complex and dynamic factors controlling urban environment.

• Journal of Korean Society of Transportation
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• v.36 no.2
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• pp.129-140
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• 2018

In this study, we analyzed the electric vehicle (EV) purchasing behavior with market segmentation in Seoul using the binary logit model. For the model estimation, the experimental design of SP survey generated 24 scenarios with purchase price, charging station availability, and driving range of EVs. The results of market segmentation analysis indicated that the owners of subcompact and compact size cars were primarily affected by the purchasing price while those of mid and full size cars were more sensitive to the charging station availability. By housing type, the charging station availability was the most important factor for the residents of apartment while the purchase price was the most important factor to choose the EVs. These results presented that the EV supply strategy of the automobile manufacturer should be diversified according to the marketing target and the expansion of the public charging infrastructure should be the top priority in the government policy.

• Journal of the Korean Society for Railway
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• v.12 no.3
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• pp.427-436
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• 2009

This paper introduced Railway Network Design Problem (RNDP) to provide priority decisions on high-speed railway investment scenarios defined by various network segments and train systems. The RNDP optimizes the objective functions of minimize total travel time. Results show that the priority of high-speed railway investment is found to be East-west, West-coast, and South-coast line respectively. An entirely new line built with 400km/h is found to be the best alternative to East-west line. Regarding West-coast and South-coast line, the combined alternative of upgrading Geolla and Kyeonjon line with 200km/h and building a new line with 400km/h and 350km/h for remains of each line is the best.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.333-341
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• 2018

Recently, there has been a growing interest in user-centered smart city services. This study examines the spatial information type to derive a smart city service scenario through space - based communication and aims to establish a direction for user - centered experience factor scenario. The results of this study are meaningful for presenting basic data to suggest a space scenario where citizens can experience smart city as walking map and experience route applicable to future smart city test bed. In particular, we simulated the walking scenarios in the smart city test bed through Walking Map, which is tested the service direction based on user requirements. Through this study, we confirmed that smart city service through existing infrastructure can be used multipurpose. The spatial information and the experience factor linkage model and the walking map through the persona model presented in this study can be utilized as a preliminary scenario applicable to the future smart city test bed.