• Journal of Communications and Networks
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• v.11 no.2
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• pp.148-156
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• 2009

The fixed spectrum assignment policy in today's wireless networks leads to inefficient spectrum usage. Cognitive radio network is a new communication paradigm that enables the unlicensed users to opportunistically use the spatio-temporally unoccupied portions of the spectrum, and hence realizing a dynamic spectrum access (DSA) methodology. Interference temperature model proposed by Federal Communications Commission (FCC) permits the unlicensed users to utilize the licensed frequencies simultaneously with the primary users provided that they adhere to the interference temperature constraints. In this paper, we formulate two NP-hard optimal scheduling methods that meet the interference temperature constraints for cognitive radio networks. The first one maximizes the network throughput, whereas the second one minimizes the scheduling delay. Furthermore, we also propose suboptimal schedulers with linear complexity, referred to as maximum frequency selection (MFS) and probabilistic frequency selection (PFS). We simulate the throughput and delay performance of the optimal as well as the suboptimal schedulers for varying number of cognitive nodes, number of primary neighbors for each cognitive node, and interference temperature limits for the frequencies. We also evaluate the performance of our proposed schedulers under both additive white gaussian noise (AWGN) channels and Gilbert-Elliot fading channels.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.1
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• pp.193-198
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• 2005

Changes in visuospatial cognitive performance, blood oxygen saturation and heart rate due to the highly concentrated oxygen administration were observed in this study. Six male ($25.8 \pm$1.0) and six female (($23.8 \pm$ 1.9) adults were asked to perform 20 visuospatial tasks with the same level of difficulties by supplying two different oxygen levels (21%, 30%). Experiment consisted of Rest1 (1 min.), Control (1 min.), Task (4 min.), and Rest2 (4 min.) and physiological signals such as blood oxygen saturation and heart rate were measured through each stage. The result showed the accuracy of task performance increased significantly at 30% oxygen concentration compared with 21%, which means oxygen supply has positive effects on visuospatial cognitive performance. When 30% oxygen was supplied, blood oxygen saturation during control and task phases was increased and heart rate was decreased compared with 21%. It means that 30% oxygen can stimulate brain activities by directly increasing the actual level of blood oxygen concentration during cognitive performance, and enough oxygen supply during cognitive performance make heart rate decrease.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.921-924
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• 2008

Recently, ultra-wideband(UWB) technology based on the transmission of short duration pulses has gained much interest for its application to wireless communications. Various wireless communication and wireless broadcast will require more efficient use of frequency. Cognitive radio technology is an intelligent technology which can sense the spectrum environment and adaptively adjust the parameters for wireless transmission. In this paper, by using Cognitive UWB, the spectrum efficiency of the transmission channels is largely improved, and the interference between the other systems can be effectively avoided.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2323-2340
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• 2012

Recent advances in cognitive radio technology have drawn immense attention to higher layer protocols above medium access control, such as transmission control protocol (TCP). Most proposals to improve the TCP performance in cognitive radio (CR) networks have assumed that either all nodes are in CR networks or the TCP sender side is in CR links. In those proposals, lower layer information such as the CR link status could be easily exploited to adjust the congestion window and improve throughput. In this paper, we consider a TCP network in which the TCP sender is located remotely over the Internet while the TCP receiver is connected by a CR link. This topology is more realistic than the earlier proposals, but the lower layer information cannot be exploited. Under this assumption, we propose an enhanced TCP protocol for CR networks called TCP for cognitive radio (TCP-CR) to improve the existing TCP by (1) detection of primary user (PU) interference by a remote sender without support from lower layers, (2) delayed congestion control (DCC) based on PU detection when the retransmission timeout (RTO) expires, and (3) exploitation of two separate scales of the congestion window adapted for PU activity. Performance evaluation demonstrated that the proposed TCP-CR achieves up to 255% improvement of the end-to-end throughput. Furthermore, we verified that the proposed TCP does not deteriorate the fairness of existing TCP flows and does not cause congestions.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.04a
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• pp.206-209
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• 2014

Control message exchange is major job for cognitive radio to exist and use spectrum opportunistically. For this control message exchange they need a common control channel (CCC). Once this channel is affected by a primary user, communication stops until new CCC is setup. This takes substantial time and if they could not get free channel, this halt continues for long time. To prevent such cease of communication, we propose a combination of two networks, namely WLAN and UWB, to let the communication continue. In our proposed idea if the CCC of a certain CR in WLAN is affected, the CR changes its network from WLAN to UWB and keeps the communication because UWB cannot be affected by PU. In the proposed idea every cognitive radio has two transceivers; one for the overlay network (WLAN) and another UWB network. If a primary user is detected in the spectrum of a cognitive radio, it continues exchanging control messages under the UWB network and in parallel negotiates for a new CCC using the WLAN network. This idea solves the communication interruption until new CCC is setup.

• Journal of the Korean Society of Safety
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• v.38 no.5
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• pp.15-26
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• 2023

The relationship between the knowledge, attitude, and practice of the person in charge of designating a Class III facility was analyzed to improve its practice. As a field of knowledge, system knowledge and technical knowledge were considered, and attitudes were divided into cognitive, affective, and behavioral attitudes. A knowledge, attitude, and practice (KAP) survey was conducted, and the relationship among them was analyzed through correlation and regression analyses. The factors affecting the level of practice in designating the Class III facility were technical knowledge in the field of knowledge and cognitive and behavioral attitudes in the field of attitudes. Cognitive and behavioral attitudes were the two factors that most influenced the practice of designating a Class III facility. It is thought that the higher the level of cognitive and behavioral attitudes, the greater the ability to practice designating the Class III facility. The general characteristics of respondents influencing cognitive and behavioral attitudes were analyzed by safety inspection.

• Journal of the Korea Safety Management & Science
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• v.14 no.3
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• pp.229-236
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• 2012

소프트웨어 기반의 시스템 설계과정에서 설계자가 고려해야 하는 요소들이 다양해지면서 시스템 설계가 점점 어려워지고 있다. 다양한 설계 요소들이 존재하지만 사용자의 특성 및 직무, 사용가능한 정보기술의 특성 등이 핵심적인 요소로 간주된다. 또한 정보기술이 발달하면서 인간과 시스템의 상호작용이 점점 인지적인 특징을 지니게 되었다. 따라서 사용성 높고, 효율적이면서 안전한 소프트웨어 기반의 시스템을 개발하기 위해서는 시스템 설계자가 사용자의 인지적인 요구사항 및 그들의 직무를 시스템 설계과정에서 체계적으로 다룰 수 있어야 한다. 그러나 소프트웨어 공학, 시스템 공학 및 인간-컴퓨터 상호작용 등에서의 전통적인 시스템 설계 방법은 이러한 설계자의 설계활동을 효과적으로 지원하는데 한계가 있었다. 그 대안으로 인지시스템공학(cognitive systems engineering; CSE)은 인간중심의 설계철학을 바탕으로 소프트웨어 기반의 복잡한 시스템 설계과정에서 설계자의 활동을 체계적으로 도와줄 수 있는 유용한 개념과 방법을 제공해주고 있다. CSE는 원래 사람이 실시간으로 감시 및 제어해야 하는 복잡한 사회기술적 시스템(예: 원자력발전소 및 공항관제소)의 분석, 설계 및 평가를 위해 태동한 학문이다. 그러나 CSE에서 제공하는 이론적 및 방법론적 프레임워크는 소프트웨어 기반의 시스템을 설계하는 데에도 유용하게 활용할 수 있는 충분한 가능성을 갖고 있다. 이 논문은 CSE의 근간을 이루는 핵심 개념 및 원칙을 고찰하고 소프트웨어 기반 시스템 설계에의 활용가능성 및 그 방안을 논의한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.6
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• pp.677-687
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• 2008

CR technology is an intelligent technology which can sense the spectrum environment an adaptively adjust the parameters for wireless transmission. In this paper, by using CR-UWB, the spectrum efficiency of the transmission channel is largely improved; Furthermore, the interference to other system can be effectively avoided. In this paper, we propose a solution on interference problem of UWB system using cognitive radio. We use interference temperature model of cognitive radio that has proposed by FCC for estimating interference signal. Calculating channel capacity of UWB system with interference temperature, we suggest how to solve interference problem. We have used genetic algorithm in cognitive engine's calculation precess. The proposed UWB System with cognitive radio shows very efficient in solving interference problem.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.35-41
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• 2017

To solve the shortage of radio spectrum and utilize spectrum resource more efficiently, cognitive radio technologies are proposed, and many studies on cognitive radio have been conducted. Multi-hop routing is one of the important technologies to enable the nodes to transmit data further with lower power in ad-hoc cognitive radio networks. In a multi-channel cognitive radio networks, each channel should be allocated to minimize interference to primary users. In the multi-hop routing, channel allocation should consider the inter-channel interference to maximize network throughput. In this paper, we propose multi-channel scheduling scheme which minimizes inter-channel interferences and avoids collision with primary users for the multi-hop multi-channel cognitive radio networks. The proposed scheduling is designed to determine both of routing path and channel selection. The performance of proposed channel allocation scheme is evaluated by the computer simulation in the aspect of capacity and collision rate.

• The Journal of Korea Robotics Society
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• v.13 no.2
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• pp.113-120
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• 2018

To fly a drone or unmanned aerial vechicle(UAV) safely, its pilot needs to maintain high situation awareness of its flight space. One of the important ways to improve the flight space awareness is to integrate both the global and the local navigation map a drone provides. However, the drone pilot often has to use the inconsistent reference frames or perspectives between the two maps. In specific, the global navigation map tends to display space information in the third-person perspective, whereas the local map tends to use the first-person perspective through the drone camera. This inconsistent perspective problem makes the pilot use mental rotation to align the different perspectives. In addition, integrating different dimensionalities (2D vs. 3D) of the two maps may aggravate the pilot's cognitive load of mental rotation. Therefore, this study aims to investigate the relation between perspective difference ($0^{\circ}$, $90^{\circ}$, $180^{\circ}$, $270^{\circ}$) and the map dimensionality matches (3D-3D vs. 3D-2D) to improve the way of integrating the two maps. The results show that the pilot's flight space awareness improves when the perspective differences are smaller and also when the dimensionalities between the two maps are matched.