• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1976-1996
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• 2011

Cognitive radio (CR) MAC protocol provides access control of unused spectrum resources without causing interference to primary users. To achieve this goal, in this paper a TDMA based cooperative multi-channel cognitive radio MAC (MCR-MAC) protocol is proposed for wireless ad hoc networks to provide reliable protection for primary users by achieving cooperative detection of incumbent system signals around the communication pair. Each CR node maintains transmission opportunity schedules and a list of available channels that is employed in the neighbor discovery period. To avoid possible signal collision between incumbent systems and cognitive radio ad hoc users, we propose a simple but efficient emergency notification message exchanging mechanism between neighbor CR nodes with little overhead. Our simulation results show that the proposed MCR-MAC can greatly reduce interference with primary users and remarkably improve the network throughput.

• Journal of information and communication convergence engineering
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• 제13권4호
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• pp.221-227
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• 2015

Spectrum sensing plays an essential role in a cognitive radio network, which enables opportunistic access to an underutilized licensed spectrum. In conventional cooperative spectrum sensing (CSS), all cognitive users (CUs) in the network spend the same amount of time on spectrum sensing and waste time in remaining silent when other CUs report their sensing results to the fusion center. This problem is solved by the superposition cooperative spectrum sensing (SPCSS) scheme, where the sensing time of a CU is extended to the reporting time of the other CUs. Subsequently, SPCSS assigns the CUs different sensing times and thus affects both the sensing performance and the throughput of the system. In this paper, we propose an algorithm to determine the optimal sensing time of each CU for SPCSS that maximizes the achieved system throughput. The simulation results prove that the proposed scheme can significantly improve the throughput of the cognitive radio network compared with the conventional CSS.

• 한국통신학회논문지
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• 제34권11A호
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• pp.822-830
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• 2009

The spectrum efficiency of mobile communication networks can be improved dramatically adopting multiple antennas technologies. In order to guarantee the licensed rights of primary user (PU), the cognitive radio system should perform in a relatively low interference manner when it gets access to the spectrum of licensed networks. In this paper, we explore a uniformly distributed circular antenna array to implement beamforming algorithm that is accomplished by optimization method at the base station of cognitive radio networks, and therefore we can suppress the interference to PU by steering quite low transmission power toward PU and constructing a narrow beam toward cognitive user (CU). By reducing the constraint number of the optimization problem, we also propose a null steering algorithm that steers rather low radiation power toward PU, while the other areas in the same cell are covered by radiation power except the local area around PU. It is pursued to reduce the computation load and enlarge the capacity of cognitive radio networks extremely. The simulation results demonstrate that the proposed algorithms process superior performance.

• International Journal of Advanced Culture Technology
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• 제6권4호
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• pp.309-316
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• 2018

The main purpose of this study is to understand how cognitive factors influence the way people interact with information/information systems, by conducting comprehensive and in-depth literature reviews and a theoretical synthesis of related research. Adaptive systems have been built around an individual user's characteristics, such as interests, preferences, knowledge and goals. Individual differences in the ability to use new information and communication technology have been an important issue in all fields. Performance differences in utilizing new information and communication technology are sufficiently predictable that we can begin to coordinate them. Therefore, it is necessary to understand cognitive mechanisms to explain differences between individuals as well as the levels of performance. The theoretical synthesis from this study can be applied to design intelligent (i.e., human friendly) systems in our everyday lives. Further research should explore optimization design for user, by integrating user's individual traits (such as emotion and intent) and system modules to improve the interactions of human-system in data-driven environments.

• 한국건설관리학회논문집
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• 제24권6호
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• pp.91-98
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• 2023

Construction accidents result from a combination of factors, including both the actions of workers and the safety conditions on site. Despite advancements in enhancing construction site safety, there remains a gap in comprehending the cognitive processes underlying workers' unsafe behavior. This paper investigates and validates a qualitative model that delves into the potential causes of workers' unsafe actions by examining their cognitive processes, employing a system dynamics approach. By analyzing the interplay of various loops within this model, it offers both short- and long-term safety strategies for managers intent on minimizing unsafe behavior among workers. Specifically, safety managers should prioritize increasing workers' awareness of hazards through education and fostering a positive safety mindset. Moreover, they should task frontline supervisors with directly addressing and rectifying instances of unsafe behavior by workers. Lastly, construction safety managers ought to formulate safety strategies that take into account the cognitive states of workers to mitigate any adverse consequences of biased safety management. The outcomes of this research contribute to our comprehension of methods to enhance hazard perception among workers, curtail unsafe actions, and ultimately reduce construction accidents from a cognitive standpoint.

• 대한인간공학회지
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• 제32권2호
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• pp.159-165
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• 2013

Objective: The aim of this study was to predict human performance time in finding objects on multi-display monitors using ACT-R cognitive architecture. Background: Display monitors are one of the representative interfaces for interaction between people and the system. Nowadays, the use of multi-display monitors is increasing so that it is necessary to research about the interaction between users and the system on multi-display monitors. Method: A cognitive model using ACT-R cognitive architecture was developed for the model-based evaluation on multi-display monitors. To develop the cognitive model, first, an experiment was performed to extract the latency about the where system of ACT-R. Then, a menu selection experiment was performed to develop a human performance model to find objects on multi-display monitors. The validation of the cognitive model was also carried out between the developed ACT-R model and empirical data. Results: As a result, no significant difference on performance time was found between the model and empirical data. Conclusion: The ACT-R cognitive architecture could be extended to model human behavior in the search of objects on multi-display monitors.. Application: This model can help predicting performance time for the model-based usability evaluation in the area of multi-display work environments.

• 산업경영시스템학회지
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• 제23권61호
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• pp.1-11
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• 2000

Ergonomic vehicle design is very important for driver's safety and sensibility. Many studies have emphasized the physical factors of human operator and usability of control devices. However, driver's cognitive factors such as the shape of cognitive map have not been well documented. The aim of this research is to find the relationship between the shape of Instrument Pane (IP) in driver's cognitive map and the real vehicle. To do this, Sketch Map Method (SMM), that is an extraction method of cognitive map, was employed to extract the shape of middle-aged driver's cognitive map. In this study, SMM was modified to formulate driver's cognitive map because this process is not being in the existing SMM. Next, correlation was analyzed between individual cognitive map and the shape of real vehicle's IP. The result showed that the position of volume control switch and cigar jack was similar between these but the position of others wasn't.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.39-44
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• 2010

본 논문에서는 최근에 많은 주목을 받고있는 상황인지 시스템을 협동릴레이 시스템에 적용하였을 때 상황인지 협동 릴레이 시스템의 성능을 유도하였다. 협동 릴레이 시스템은 기회전송 릴레이를 채택하였을 때와 채택하지 않았을 때의 성능을 비교하였다. 특히 목적지에서 시스템 구현의 간편성 때문에 많이 채택하고 있는 선택 결합방식을 고려하였는데, 이 경우 필수적으로 발생되는 채널 상태 정보(CSI)를 주고받으면서 발생되는 지연의 영향을 고려하였다. 분석결과 기회전송 릴레이를 채택할 경우 기회전송 릴레이를 채택하지 않은 경우보다 주어진 조건에서 최대 0.6 dB 열화 되었으며, 시스템의 성능은 상황인지 릴레이의 주파수 획득 확률보다는 채널 상태정보의 지연에 더욱 민감한 영향을 받음을 알 수 있었다.

• 한국도서관정보학회지
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• 제22권
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• pp.245-276
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• 1995

This study analyzed the process of information service and its factors in the cognitive viewpoint. And developed a conceptual model to help in developing future information systems and services. The results of this study were summarized as follows : 1) The paradigm of information user study is changing from the system-centered to the user-centered one. 2) The researchers describe the user's internal cognitive process as the starting point of the information service. 3) The user's personal cognitive process influence the process of the information service over. And the focus is a microscopic one including the factors of the perception and recognition of the stimulus, remembering and searching information, reasoning the rules, recognition of the patterns, formalization of the concepts, etc. 4) The information librarian performs the role as a knowledge/ information system interface, and his knowledge structure reflects the organization of that knowledge/information system. 5) The information librarians can perform their role as information specialists actively and offensively. And the performance of the librarians can be measured on the scales of the su n.0, pplying capability of relevant information and the client satisfaction.

• 한국시스템다이내믹스연구
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• 제5권1호
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• pp.127-142
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• 2004

Feedback loop dominance is a key concept to understand structural driving forces of system behavior. In this paper, we propose two kinds of shifts in dominant feedback loops: continuous shifts (CS) and discrete shifts (DS). With the help of questionnaires, we verified three hypotheses regarding cognitive biases in perceiving the shifts in dominant feedback loops: 1) failure in perceiving continuous shifts, 2) tendency of decision making based on discrete shifts, and 3) different perception on the dominant feedback loops between level variables and rate variables. We discussed the implication of these cognitive biases on time delay and timing strategy in decision-making processes.