• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.28-35
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• 2011

Cooperative ARQ scheme is effective for better QoS guarantee for the next generation mobile communication systems where multimedia data transmission highly increases. In this paper, we propose a cooperative ARQ strategy in ad hoc cognitive relays for mobile multimedia communication for supporting instantaneous cooperation in MANET environment. In the proposed strategy, to support real time, delay-sensitive services, whenever a frame is transmitted from the source, each relay actively senses the SINR of the signal transmitted from the source, and determine whether to propose retransmission or not before the destination transmits feedback signal. To minimize the false retransmission decision or needless retransmission, we propose an adaptive sensing threshold optimization algorithm to maintain suboptimal sensing thresholds for each relay. By computer simulation, it is shown that the proposed cooperative ARQ retransmission scheme outperforms the conventional schemes with respect to frame transmission delay and frame loss probability in real time multimedia data transmission system.

• Korean Journal of Organic Agriculture
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• v.28 no.4
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• pp.477-490
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• 2020

In this paper, the factors influencing the differentiation of environment-friendly agricultural products from the intention of environment-friendly farming experience were analyzed through logit analysis. The main analysis results are summarized as follows. First, the contents to experience in environment-friendly agricultural innovation in Jeonnam province are environment-friendly agricultural product harvesting (33.8%), making food using environment-friendly agricultural products (24.1%) and environment-friendly ecological experience (20.1%). Second, significant variables affecting the intention to experience environment-friendly agriculture were analyzed as whether they were members of the consumer cooperative, whether they were children under the age of two, and whether they were children under the age of high school. In other words, it was analyzed that the more members of the consumer cooperative, the more families with children under the age of two, and the more families with student children, the more likely they are to participate in environment-friendly farming experiences. Third, significant variables that affect the recognition of the differentiation of environment-friendly agricultural products in Jeonnam province were found to be environment education and dual income. In other words, it is analyzed that consumers who receive environment education and dual-income families are more likely to recognize environment-friendly agricultural products in Jeonnam province differently than in other regions.

• Journal of Environmental Impact Assessment
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• v.18 no.1
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• pp.51-57
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• 2009

Corylopsis coreana Uyeki is endemic species in the Korean peninsula and is designated a Category Endangered Plant Species by the Wildlife Protection Act of South Korea. We developed the plan and cooperative model within the local community for the species conservation. In order to carry out this plan we first investigated the ecological characteristics of the species. The species shows patterns of discontinuous distribution and is coupled with the unusual feature of only growing on northern exposed slopes. Although Corylopsis coreana is cut the stem every year, many new sprouts are still grown from the root. Natural germination of the seed occurs only on north-facing slopes, but not on south-facing slopes at spring. That is, the species is highly influenced by soil moisture until the seedling stage has been reached. This factor limits the distribution of the species. When saplings are planted on south-facing slopes, they grow well. The information we gathered greatly helped with efforts to draw up conservation plans. In addition, when the information was shared with the local community, builders and residents showed great interest and displayed a will to help with conservation efforts. Therefore, a cooperative model within the local community was drawn up for the conservation of the species. Accordingly this model could be applied at mitigation measure at environment impact assessment.

• Journal of the Korean Society of Earth Science Education
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• v.2 no.1
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• pp.41-47
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• 2009

This study examined the difference for the ability of self-directed learning and information literacy(the ability to use information) between small group-cooperative instruction of ICT practical environment and explanatory instruction using ICT of general classroom in middle school science education. The 138 students(7th grade) participated in this study were classified in two group, experimental group(68) and controlled group(70). Experimental small group consisted of 5-6 students who had different levels and the ability of each the group was equal. The teaching of experimental group was made in the science lab which was equipped with computers to connect super high-speed Internet. The teaching of control group was made in general classroom. Under these two environment, this study was executed during 10 weeks. As the result, Small group-cooperative learning using ICT was more effective in diminishing the gap of information literacy in middle school students. And in the ability of self-directed learning, the small group learning using ICT was also more effective than general classroom instruction.

• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.450-462
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• 2004

In this paper, we describe a system for controlling the perceptual processes of two cooperative mobile robots that addresses the issue of enhancing perceptual awareness. We define awareness here as knowing the location of other robots in the environment. The proposed system benefits from a formalism called perceptual anchoring. Here, perceptual anchoring enhances the awareness of the system by employing an anchor-based active gaze control strategy or active perceptual anchoring to control the perceptual effort according to what is important at a given time. By anchoring we extend the notion of awareness as knowing what the symbols in the control module represent to by connecting them to the objects or features in the environment. We demonstrate the present system through a simulation of two nonholonomic mobile robots performing a cooperative transportation by carrying a cargo to a target location where there are two other robots moving about. The system is able to efficiently focus the perceptual effort and thus able to safely carry the cargo to the target position.

• Journal of Korean Elementary Science Education
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• v.27 no.4
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• pp.446-454
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• 2008

The purpose of this study was to examined the effects of different grouping according to the levels of students' achievement in science cooperative learning on students' science academic achievements, science-related attitudes, perceptions of science learning environment and self-efficacies. The results of this study can be summarized as following. First, the homogeneous grouping was more effective than the heterogeneous grouping in improving the science academic achievements of high academic ability students. Second, the homogeneous grouping was more effective than the heterogeneous grouping in improving the science-related attitude of students, especially for low academic ability students. Third, both the homogeneous grouping and the heterogeneous grouping improved the perceptions of science learning environment of students. For low academic ability students, the homogeneous grouping was more effective. Fourth, the homogeneous grouping was more effective than the heterogeneous grouping in improving self-efficacies of students, especially for middle and low academic ability students.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.127-132
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• 2016

For a practical mobile robot team such as carrying out a search and rescue mission in a disaster area, the localization have to be guaranteed even in an environment where the network infrastructure is destroyed or a global positioning system (GPS) is unavailable. The proposed architecture supports localizing robots seamlessly by finding their relative locations while moving from a global outdoor environment to a local indoor position. The proposed schemes use a cooperative positioning system (CPS) based on the two-way ranging (TWR) technique. In the proposed TWR-based CPS, each non-localized mobile robot act as tag, and finds its position using bilateral range measurements of all localized mobile robots. The localized mobile robots act as anchors, and support the localization of mobile robots in the GPS-shadow region such as an indoor environment. As a tag localizes its position with anchors, the position error of the anchor propagates to the tag, and the position error of the tag accumulates the position errors of the anchor. To minimize the effect of error propagation, this paper suggests the new scheme of full-mesh based CPS for improving the position accuracy. The proposed schemes assuring localization were validated through experiment results.

• Journal of Auto-vehicle Safety Association
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• v.15 no.3
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• pp.34-42
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• 2023

Simulation-based virtual testing is known to be a major requirement for verifying the safety of autonomous driving functions. However, in the simulation environment, there is a difficulty in that all driving environments related to the autonomous driving system must be realistically modeled. In particular, C-ITS (Cooperative-Intelligent Transport Systems) is essential for urban autonomous driving of Lv.4, but the approach to modeling for C-ITS service in the MILS (Model in the Loop Simulation) environment is not yet clear. Therefore, this paper aims to deal with V2X (Vehicle to Everything) modeling methods to effectively apply C-ITS-based autonomous cooperative driving services in the MILS environment. First, major C-ITS services and use cases for autonomous cooperative driving are analyzed, and a modeling method of V2X signals for C-ITS service simulation is proposed. Based on the modeled V2X messages, the validity of the proposed approach is reviewed through simulations on the C-ITS service use case.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.148-155
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• 2008

In wireless data communication systems, retransmission of an erroneous packet is inevitable due to the harsh communication environment. In this paper, an efficient retransmission scheme using cooperation from neighboring nodes is investigated. In the cooperative retransmission scheme, an erroneous packet is transmitted to the destination by cooperative nodes which have favorable channels. This cooperative retransmission scheme requires no a priori information of neighboring nodes and has no limitation on the number of cooperating nodes. Distributed beamforming is used to accommodate multiple cooperating nodes. Phase and frequency offsets of cooperating signals are extracted from the NACK message and used to co-phase retransmitted data packets. The outage probability of the cooperative retransmission scheme is analyzed for the case of perfect synchronization and when the offsets are estimated. To reduce the impact of the residual phase and frequency offsets in cooperating signals, a low-rate feedback scheme is also investigated. It is shown that improved outage probability and reduced packet error rate (PER) performance can be achieved even for long data packets. The proposed cooperative retransmission scheme is found to outperform simple retransmission by the source as well as decode-and-forward cooperation.

• Journal of Communications and Networks
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• v.13 no.3
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• pp.240-249
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• 2011

Cooperative diversity protocols have attracted a great deal of attention since they are thought to be capable of providing diversity multiplexing tradeoff among single antenna wireless devices. In the high signal-to-noise ratio (SNR) region, cooperation is rarely required; hence, the spectral efficiency of the cooperative protocol can be improved by applying a proper cooperation selection technique. In this paper, we present a simple "cooperation selection" technique based on instantaneous channel measurement to improve the spectral efficiency of cooperative protocols. We show that the same instantaneous channel measurement can also be used for relay selection. In this paper two protocols are proposed-proactive and reactive; the selection of one of these protocols depends on whether the decision of cooperation selection is made before or after the transmission of the source. These protocols can successfully select cooperation along with the best relay from a set of available M relays. If the instantaneous source-to-destination channel is strong enough to support the system requirements, then the source simply transmits to the destination as a noncooperative direct transmission; otherwise, a cooperative transmission with the help of the selected best relay is chosen by the system. Analysis and simulation results show that these protocols can achieve higher order diversity with improved spectral efficiency, i.e., a higher diversity-multiplexing tradeoff in a slow-fading environment.