• 한국위성정보통신학회논문지
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• 제7권1호
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• pp.7-12
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• 2012

본 논문에서는 인지무선통신에서 중요한 기술 중 하나인 스펙트럼 센싱의 Hidden node의 문제나 셀룰라 시스템에서 셀 경계에서 CPE(Customer-Primise equipments)의 낮은 SNR(Signal to Noise Ratio)로 인한 센싱 성능 저하를 해결하기 위해 CPE들의 협력릴레이 기법을 사용한 협력 스펙트럼 센싱을 제안하고 검출확률 성능을 분석한다. 송신단과 수신단 사이의 릴레이(Relay) 적용된 협력 스펙트럼 센싱은 가상의 공간 다이버시티이득(Spatial Diversity Gain)을 얻을 수 있어 센싱 성능이 향상된다. 협력 통신 기법 중 AF(Amplify and Forward)와 DF(Decoded and Forward)방식이 대표적이다. 따라서 이 두가지 협력통신 기법을 적용하여 협력스펙트럼 센싱의 검출확률의 성능을 비교하고 분석한다.

• 한국의류산업학회지
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• 제23권3호
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• pp.323-336
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• 2021

This study investigated the cognitive process of fashion design images through eye activity tracking. Differences in the cognitive process and gaze activity according to image elements were confirmed. The results of the study are as follows. First, a difference was found between groups in the gaze time for each section according to the model and design. Although model diversity is an important factor leading the interest of observers, the simplicity of the model was deemed more effective for observing the design. Second, the examination of the differences by segments regarding the gaze weight of the image area showed differences for each group. When a similar type of model is repeated, the proportion of face recognition decreases, and the proportion of design recognition time increases. Conversely, when the model diversity is high, the same amount of time is devoted to recognizing the model's face in all the processes. Additionally, there was a difference in the gaze activity in recognizing the same design according to the type of model. These results enabled the confirmation of the importance of the model as an image recognition factor in fashion design. In the fashion industry, it is important to find a cognitive factor that attracts and retains consumers' attention. If the design recognition effect is further maximized by finding service points to be utilized, the brand's sustainability is expected to be enhanced even in the rapidly changing fashion industry.

• 전자공학회논문지
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• 제51권4호
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• pp.3-9
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• 2014

ECMA-392는 개인 휴대용 장치를 위한 최초의 CR (cognitive radio) 표준으로서, 2개까지의 전송 안테나를 지원하며 이를 위한 전송 다이버시티 기법으로는 개방루프 방식만을 지원한다. 본 논문에서는 ECMA-392 시스템을 위한 간단한 형태의 부반송파 그룹핑(sub-carrier grouping) 기반 폐루프 전송 다이버시티 기법을 설계하고자 한다. ECMA-392 시스템에 적합한 부반송파 그룹핑 방법을 제시할 것이며, 각각의 부 반송파 그룹에 대해 채널 환경에 따른 전송 안테나 선택 방법을 제안한다. 이때 피드백 정보량을 줄이기 위해, 채널 환경에 따른 전송 안테나 결정을 수신단에서 하고 결정된 전송 안테나의 인덱스 값만을 송신단에 보내주는 방식을 사용한다. ECMA-392 표준에서 제시하는 개방루프 전송 다이버시티 기법들과의 성능비교를 통해, ECMA-392 시스템에 폐루프 전송 다이버시티 기법의 도입 여부에 대한 판단 근거를 제시하고자 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.632-650
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• 2013

The paper considers a spectrum sharing cognitive radio (CR) network coexisting with a primary network under the average interference power constraint. In particular, the secondary user (SU) is assumed to carry delay-sensitive services and thus shall satisfy a given delay quality-of-service (QoS) constraint. The secondary receiver is also assumed to be equipped with multiple antennas to perform maximal ratio combining (MRC) to enhance SU performance. We investigate the effective capacity of the SU with MRC diversity under aforementioned constraints in Nakagami fading environments. Particularly, we derive the optimal power allocation to achieve the maximum effective capacity of the SU, and further derive the effective capacity in closed-form. In addition, we further obtain the closed-form expressions for the effective capacities under three widely used power and rate adaptive transmission schemes, namely, optimal simultaneous power and rate adaptation (opra), truncated channel inversion with fixed rate (tifr) and channel inversion with fixed rate without truncation (cifr). Numerical results supported by simulations are presented to consolidate our studies. The impacts on the effective capacity of various system parameters such as the number of antennas, the average interference power constraint and the delay QoS constraint are investigated in detail. It is shown that MRC diversity can significantly improve the effective capacity of the SU especially for cifr transmission scheme.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.185-186
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• 2008

We propose an efficient spectrum sensing scheme for cognitive radio systems with multiple antennas. By utilizing the property of multiple receive antennas, spectrum sensing without idle period is possible. Simulation results show that the detection probability is enhanced with the number of receive antennas, which explains the effect of the spatial diversity.

• 정보통신설비학회논문지
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• 제8권3호
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• pp.111-115
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• 2009

Cognitive Radio (CR) technology is proposed for using the unused spectrum band efficiently because of the spectrum scarcity problems. Spectrum sensing is one of the most challenging issues in cognitive radio system. In this paper, we focus on the signal detection of WiBro system band. As most of the modulated signals can be treated as cyclostationary random process, we can detect the signal of the OFDM signals in WiBro system. OFDM symbols using WiBro system have several pilot subcarriers and periodic pilots have cyclostationary characteristic. To improve the detection performance, we get diversity gain using multiple antennas.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2047-2066
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• 2016

In this paper, we investigate joint power allocation and relay selection (PARS) schemes in non-orthogonal cooperative protocol (NOCP) based cognitive relay networks. Generally, NOCP outperforms the orthogonal cooperative protocol (OCP), since it can provide more transmit diversity. However, most existing PARS schemes in cognitive relay networks focus on OCP, which are not suitable for NOCP. In the context of NOCP, we first derive the joint constraints of transmit power limit for secondary user (SU) and interference constraint for primary user (PU). Then we formulate optimization problems under the aforementioned constraints to maximize the capacity of SU in amplify-and-forward (AF) and decode-and-forward (DF) modes, respectively. Correspondingly, we derive the closed form solutions with respect to different parameters. Numerical results are provided to verify the performance improvement of the proposed PARS schemes.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.379-383
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• 2008

Cognitive Radio (CR) technology is proposed for using the unused spectrum band efficiently because of the spectrum scarcity problems. Spectrum sensing is one of the most challenging issues in cognitive radio system. In this paper, we focus on the signal detection of WiBro system band. As most of the modulated signals can be treated as cyclostationary random process, we can detect the signal of the OFDM signals in WiBro system. OFDM symbols using WiBro system have several pilot subcarriers and periodic pilots have cyclostationary characteristic. To improve of the detection performance, we get diversity gain using multiple antennas.

• Journal of Nutrition and Health
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• 제31권9호
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• pp.1457-1467
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• 1998

The relationship between cognitive function and dietary patterns in Korean elderly women was investigated in this study. Twenty-four-hour dietary recall and cognitive function tests were performed in 170 elderly women aged over 60 years. Average age of the subjects was 71 years and the average number of family members was 3.3. Most of the subjects had less than seven years of education and their monthly income was much lower than the Korean average. Most of the subjects engaged in regular exercise and did not indulge in drinking and smoking. The average cognitive function score of the subjects was 58.4. Most of the subjects appeared to consume insufficient amount of food ; average intakes of energy, Ca, iron, vitamin A, and riboflavin were lower than RDA for the elderly. Cognitive function score was positively related to education level and regularity of exercise. Also, cognitive function score had a strong relationship with food intake such as total amounts of foods, fish and shellfish, milk and dairy products, total animal food, fruit, bread and sugar. Energy, protein, Ca, p, riboflavin, and niacin were also shown to have positive relationships to cognitive function score, while carbohydrate caloric ratio had a negative relationship with cognitive function. According to the results of multiple regression analysis, factors that most influenced on cognitive function were education level and riboflavin intake. The subjects who had more than seven years of education had significantly higher cognitive function scores than those with no school education. And cognitive function scores f3r those who consumed more than 2/3 of the RDA for most nutrients were significantly higher than the ones fir the subjects who consumed less than 2/3 of the RDA. These results suggest that proper education and adequate nutrient intake in quantity and quality by achieving food diversity are essential in maintaining cognitive function in later life (Korean J Nutrition 31(9) : 1457-1467, 1998)

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권3호
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• pp.924-944
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• 2014

This paper investigates the power allocation and outage performance of MIMO full-duplex relaying (MFDR), based on orthogonal space-time block codes (OSTBC), in cognitive radio systems. OSTBC transmission is used as a simple means to achieve multi-antenna diversity gain. Cognitive MFDR systems not only have the advantage of increasing spectral efficiency through spectrum sharing, but they can also extend coverage through the use of relays. In cognitive MFDR systems, the primary user experiences interference from the secondary source and relay simultaneously, owing to full duplexing. It is therefore necessary to optimize the transmission powers at the secondary source and relay. In this paper, we propose an optimal power allocation (OPA) scheme based on minimizing the outage probability in cognitive MFDR systems. We also analyse the outage probability of the secondary user in noise-limited and interference-limited environments in Nakagami-m fading channels. Simulation results show that the proposed schemes achieve performance improvements in terms of reducing outage probability.