• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.53-58
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• 2012

With a game-theoretic view, p-persistence slotted ALOHA is structured as a non-cooperative game, in which a Nash equilibrium is sought to provide a value for the probability of attempting to deliver a packet. An expression of Nash equilibrium necessarily includes the number of active outer stations, which is hardly available in many practical applications. In this paper, we thus propose a Bayesian scheme of predicting the number of active outer stations prior to deciding whether to attempt to deliver a packet or not. Despite only requiring the minimal information that an outer station is genetically able to acquire by itself, the Bayesian scheme demonstrates the competitive predicting performance against a method which depends on heavy information.

• Industrial Engineering and Management Systems
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• v.12 no.3
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• pp.264-273
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• 2013

Credit option is a policy that has been studied by many researchers in the area of supply chain management. This policy has been applied in practice to improve the profits of supply chain members. Usually, a credit option policy is proposed by the seller, and often under a symmetric information environment where members have complete information on each others' operations. In this paper, we investigate two scenarios: firstly, the seller offers a credit option to the buyer, and secondly, the buyer attempts to stretch the length of the credit period offered by the seller. The proposed model in both scenarios will be investigated under an asymmetric information structure where some information are private and are only known to the individual who has knowledge of this information. The interactions between buyer and seller will be modeled by non-cooperative Stackelberg games where the buyer and seller take turn as leader and follower. Among some of the numerical results obtained, the seller and buyer's profits obtained from symmetric information games are larger than those obtained from an asymmetric information game in both scenarios. Furthermore, both buyer and seller's profit in the second scenario are better than in the first scenario.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.5
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• pp.680-687
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• 2014

PGA(phase gradient autofocus) has been widely used to remove motion induced phase errors in the ISAR(inverse synthetic aperture radar) imaging. The critical process for the processing time and image quality is windowing stage in PGA. In this paper, the new method to determine window size based on polynomial least square approximation is proposed. Moreover, dominant range bins are selected for efficient phase error estimation, which improve image quality and speed up convergence. The simulation results show that the proposed algorithm provides high quality ISAR images while computational efficiency of inherent PGA is retained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1721-1735
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• 2016

Power-efficient base station (BS) operation is one of the important issues in future green cellular networks. Previously well-known BS operation schemes, the cell zooming scheme and the cell wilting and blossoming scheme, require tight cooperation between cells in cellular networks. With the previous schemes, the non-cooperative BSs of a serving cell and neighboring cells could cause coverage holes between the cells, thereby seriously degrading the quality of service as well as the power saving efficiency of the cellular networks. In this paper, we propose a novel power-efficient BS operation scheme for green downlink heterogeneous cellular networks, in which the networks virtually adjust the coverage of a serving macrocell (SM) and neighboring macrocells (NMs) without adjusting the transmission power of the BSs when the SM is lightly loaded, and the networks turn off the BS of the SM when none of active users are associated with the SM. Simulation results show that our proposed scheme significantly improves the power saving efficiency without degrading the quality of service (e.g., system throughput) of a downlink heterogeneous LTE network and outperforms the previous schemes in terms of system throughput and power saving efficiency. In particular, with the proposed scheme, macrocells are able to operate independently without the cooperation of a SM and NMs for green heterogeneous cellular networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3432-3448
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• 2015

Interference can cause serious problems in our daily life. Traditional ways in localizing a target can't work well when it comes to the source of interference for it may take an uncooperative or even resistant attitude towards localization. To tackle this issue, we take the BPSN (Binary Proximity Sensor Networks) and consider a passive way in this paper. No cooperation is needed and it is based on simple sensor node suitable for large-scale deployment. By dividing the sensing field into different patches, when enough patches are formed, good localization accuracy can be achieved with high resolution. Then we analyze the relationship between sensing radius and localization error, we find that in a finite region where edge effect can't be ignored, the trend between sensing radius and localization error is not always consistent. Through theoretical analysis and simulation, we explore to determine the best sensing radius to achieve high localization accuracy.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.6
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• pp.579-589
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• 2016

This research focuses on accomplishing analysis problems and issues by examining the policies and systems related to geo-spatial big data which have recently arisen, and suggests political and systemic improvement plan for service activation. To do this, problems and probable issues concerning geo-spatial big data service activation should be analyzed through the examination of precedent studies, policies and planning, pilot projects, the current legislative situation regarding geo-spatial big data, both domestic and abroad. Therefore, eight political and systematical improvement plan proposals are suggested for geo-spatial big data service activation: legislative-related issues regarding geo-spatial big data, establishing an exclusive organization in charge of geospatial big data, setting up systems for cooperative governance, establishing subsequent systems, preparing non-identifying standards for personal information, providing measures for activating civil information, data standardization on geo-spatial big data analysis, developing analysis techniques for geo-spatial big data, etc. Consistent governmental problem-solving approaches should be required to make these suggestions effectively proceed.

• World Technopolis Review
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• v.3 no.3
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• pp.139-152
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• 2014

The current transportation regime is largely based on two alternatives: (1) fixed route public transit, and (2) private ownership of internal combustion engine (ICE) powered vehicles per households. This paper analyzes one possible transportation alternative, Micro Electric Vehicles or MEVs, and compares with the ICE vehicles in terms of social, economic and environmental benefits, especially emphasizing its environmental advantage over ICE vehicles for future sustainability. While some representative models of MEVs exist in a limited market capacity, but global technical standards are generally insufficient and non-homogenous across nations, which restricts the development of the proposed transportation sector. The focus of this paper is to analyze the characteristics and potential benefits of MEVs in economical and environmental perspectives, including development status and technical standards, with a particular focus in the E.U., the U.S., Japan, and Korea. Based on the data of analysis, this paper aims to derive and propose a cooperative and adaptive global policy framework designed to speed up adoption and expansion of the global MEV market, including passenger and utility vehicles. We propose MEV to be a new mobility segment in the global transportation market because of their advantage in environmental impact, sustainability, overall cost of ownership, and safety.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4432-4450
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• 2014

It is widely observed that in practical wireless cooperative communication systems, different links may experience different fading characteristics. In this paper, we investigate into the outage probability and channel capacity of two-way amplify-and-forward (TWAF) relaying systems operating over a mixed asymmetric Rician and Rayleigh fading scenario, with different amplification policies (AP) adopted at the relay, respectively. As TWAF relay network carries concurrent traffics towards two opposite directions, both end-to-end and overall performance metrics were considered. In detail, both uniform exact expressions and simplified asymptotic expressions for the end-to-end outage probability (OP) were presented, based on which the system overall OP was studied under the condition of the two source nodes having non-identical traffic requirements. Furthermore, exact expressions for tight lower bounds as well as high SNR approximations of channel capacity of the considered scenario were presented. For both OP and channel capacity, with different APs, effective power allocation (PA) schemes under different constraints were given to optimize the system performance. Extensive simulations were carried out to verify the analytical results and to demonstrate the impact of channel asymmetry on the system performance.

• Journal of Communications and Networks
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• v.17 no.5
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• pp.499-505
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• 2015

We analyze the performance of multistage cooperation in decode-and-forward relay networks where the transmission between source and destination takes place in $T{\geq}2$ equal duration and orthogonal time phases with the help of relays. The source transmits only in the first time phase. All relays that can decode the source's transmission forward the source's message to the destination in the second time phase, using a space-time code. During subsequent time phases, the relays that have successfully decoded the source message using information from all previous transmitting relays, transmit the space-time coded symbols for the source's message. The non-decoding relays keep accumulating information and transmit in the later stages when they are able to decode. This process continues for T cooperation phases. We develop and analyze the outage probability of multistage cooperation protocol under orthogonal relaying. Through analytical results, we obtain the near-optimal placement strategy for relays that gives the best performance when compared with most other candidate relay location strategies of interest. For different relay network topologies, we also investigate an interesting tradeoff between an increased SNR and decreased spectral efficiency as the number of cooperation stages is increased. It is also shown that the largest multistage cooperation gain is obtained in the low and moderate SNR regime.

• Journal of the Korean association of regional geographers
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• v.21 no.2
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• pp.226-241
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• 2015

This research aims to analyse rural change by increasing in urban-to-rural migrants in rural Jeju. In particular, the author analysed changes in rural area focusing on non-agricultural sector and local organization. Urban-to-rural migrants into rural Jeju have been causing increase in tourism business. Such an increase in tourism business caused increase in construction of service space and changes in land use. Meanwhile, the local organization formed by urban-to-rural migrants has differences in its members and its activities and implementing system of activities in comparison with those of native local organizations. The Seowgipo Rural Migrants Cooperative, which is the research target, has characters of urbanism even thoug it was formed in rural area.