• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3080-3099
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• 2016

In this paper, we propose an algorithm for energy efficient cooperative communication in wireless sensor network (WSN). The algorithm computes the appropriate transmission distance corresponding to optimal broadcast bit error probability, while taking the circuit energy consumption and the number of cooperating nodes into consideration. The algorithm guarantees minimum energy consumption by choosing higher value of bit error probability for cooperative phase and lower value of bit error probability for broadcast phase while maintaining the required end-to-end reliability. The simulation results show that the proposed algorithm provides significant energy saving gain when compared with traditional fixed distance schemes and is suitable for applications demanding energy efficiency with high quality of reception.

• ETRI Journal
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• 제43권1호
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• pp.17-30
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• 2021

At present, multiple input multiple output radars offer accurate target detection and better target parameter estimation with higher resolution in high-speed wireless communication systems. This study focuses primarily on power allocation to improve the performance of radars owing to the sparsity of targets in the spatial velocity domain. First, the radars are clustered using the kernel fuzzy C-means algorithm. Next, cooperative and noncooperative clusters are extracted based on the distance measured using the kernel fuzzy C-means algorithm. The power is allocated to cooperative clusters using the Pareto optimality particle swarm optimization algorithm. In addition, the Nash equilibrium particle swarm optimization algorithm is used for allocating power in the noncooperative clusters. The process of allocating power to cooperative and noncooperative clusters reduces the overall transmission power of the radars. In the experimental section, the proposed method obtained the power consumption of 0.014 to 0.0119 at K = 2, M = 3 and K = 2, M = 3, which is better compared to the existing methodologies-generalized Nash game and cooperative and noncooperative game theory.

• 한국정보통신학회논문지
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• 제17권8호
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• pp.1811-1819
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• 2013

본 논문에서는 무선통신에서의 시스템 성능을 향상시키기 위해 협력통신에서 매우 중요한 도움노드를 선정하는 방법에 대하여 연구를 수행하였다. 본 논문에서 제안한 BT-COMAC (busy tone cooperative MAC) 프로토콜은 사후(reactive) 도움노드 선정기법을 채용하였으며, 기존 기법의 장점을 극대화하면서 단점을 보완한 새로운 협력통신용 MAC 프로토콜이다. 컴퓨터 모의실험을 통해 성능평가를 수행하였으며, 시스템 처리량과 채널 액세스 지연시간을 성능평가 척도로 사용하였다. 모든 통신노드들이 통신영역 내에서 독자적으로 움직이는 이동성 모델을 사용하였으며, 슬로우 페이딩 채널 환경에서 수신 전력을 기반으로 전송속도를 결정하는 방법을 사용하였다. 성능평가 결과 본 논문에서 제안한 기법이 기존 방식에 비해 시스템 처리량 측면에서 최대 15% 정도 성능개선을 달성한 것을 확인할 수 있었다.

• 한국과학교육학회지
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• 제20권1호
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• pp.174-182
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• 2000

본 연구에서는 협동학습을 적용한 공통과학 수업에서 학생의 의사소통 불안 수준을 고려한 소집단 구성의 효과와 의사소통 불안에 따른 차이를 조사하였다. 고등학교 세 학급 (112명)을 협동학습 두 반과 전통학습 한 반으로 무선 배치하였다. 협동학습 두 반의 학생들을 의사소통 불안 검사 점수에 기초한 의사소통 불안 수준에 따라서 이질 집단과 동질 집단으로 구성하였다. 11차시 동안 물질에 관한 수업 후, 학업 성취도, 자아존중감, 과학 학습 동기, 그리고 협동학습 과정에서의 의사소통 능력 부족에 대한 인식과 도움 받기에 대한 기대감을 조사하였다. 이원 변량 분석 결과 학업 성취도에서는 주효과나 상호작용 효과가 없었다. 그러나, 과학 학습 동기의 네 하위 범주 가운데 관련성과 만족감 점수에서 수업 처치의 주효과가 유의미하였다. 사후 비교에서 이질 집단의 점수가 통제 집단보다 유의미하게 높았다. 협동학습 과정에서의 도움 받기에 대한 기대감에 대해서는 이질 집단의 점수가 동질 집단보다 높았다. 의사소통 불안 상위 수준의 학생들은 하위 수준보다 자아존중감이 더 낮았고, 의사소통 능력에 대한 부족함을 많이 느꼈다.

• Journal of Communications and Networks
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• 제15권5호
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• pp.457-463
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• 2013

In recent days, cooperative diversity and communication security become important research issues for wireless communications. In this paper, to achieve low probability of interception (LPI) and high throughput in the cooperative single-carrier frequency division multiple access (SC-FDMA) system, a new physical layer transmission scheme is proposed, where a new encryption algorithm is applied and adaptive modulation is further considered based on channel state information (CSI). By doing so, neither relay node nor eavesdropper can intercept the information signals transmitted from user terminal (UT). Simulation results show above new physical layer transmission scheme brings in high transmission safety and secrecy rate. Furthermore, by applying adaptive modulation and coding (AMC) technique according to CSI, transmission throughput can be increased significantly. Additionally, low peak-to-average power ratio (PAPR) characteristic can still be remained due to the uniform distribution of random coefficients used for encryption algorithm.

• 한국간호교육학회지
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• 제16권2호
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• pp.202-212
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• 2010

Purpose: The purpose of this study was to identify the effectiveness of the JigsawⅣ cooperative learning in a facilitative communication class of nursing students. Achievement, communication skill, self-directed learning and experience during the class were measured. Method: This study was a pretest and posttest design with two subject groups. 43 students were in experimental (JigsawⅣ) group and 47 ones were in control (general small discussion) group. Classes were conducted over a 6-week period. The collected data was analyzed by the SPSS 12.0 program. Result: After taking part in the educational program, the experimental group had significantly more improvement in communication skill (F=6.81, p=.002) and self-directed learning (F=11.81, p=.000). In addition, the experimental group showed significantly higher scores for concentration in the class (t=2.26, p=.27), positive emotional state (t=3.01, p=.003) and active participation (t=2.78, p=.007) compared to the control group. However, the achievement between the two groups was not significantly different (F=3.29, p=.073). Conclusion: The findings of this study show that JigsawⅣ cooperative learning has positive effects in improvement of communication skill and self-directed learning. Also, students were excited and interested in the class during cooperative learning. Based on these findings, the author suggests developing additional educational programs focusing on nursing students.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2838-2858
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• 2019

Traditional channel models for vehicle-to-vehicle (V2V) communication usually assume fixed velocity in static scattering environment. In the realistic scenarios, however, time-variant velocity for V2V results in non-stationary statistical properties of wireless channels. Dynamic scatterers with random velocities and directions have been always utilized to depict the non-stationary statistical properties of the channel. In this paper, a non-stationary geometry-based cooperative scattering channel model is proposed for multiple-input multiple-output (MIMO) V2V communication systems, where a birth-death process is used to capture the appearance and disappearance dynamic properties of moving scatterers that reflect the time-variant time correlation and Doppler spectrum characteristics. Moreover, our model has more straight and concise to study the impact of the vehicular traffic density on channel characteristics and thus avoid complicated procedure in deriving the analytical expressions of the channel parameters and functions. The numerical results validate our analysis and demonstrate that setting important parameters of our model can appropriately build up more purposeful measurement campaigns in the future.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.13-19
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• 2012

In this paper, we investigate cooperative transmission in one-dimensional random wireless networks. In this scheme, a stationary source communicates with a stationary destination with the help of N relays, which are randomly placed in a one-dimensional network. We derive exact and approximate expressions of the average outage probability over Rayleigh fading channels. Various Monte-Carlo simulations are presented to verify the accuracy of our analyses.

• Journal of electromagnetic engineering and science
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• 제9권2호
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• pp.66-70
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• 2009

The decode-and-forward cooperative communication protocol allows single-antenna users in wireless environments to obtain the powerful benefits of multi-antenna systems without the need for physical arrays. Evaluating the performance of this protocol through simulations is time-consuming and therefore, a need exists for an analytical BER expression to serve as a reference. This paper proposed such an expression for coherently BPSK-modulated data.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2011년도 한국컴퓨터종합학술대회논문집 Vol.38 No.1(D)
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• pp.267-268
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• 2011

Recent research activities in cooperative communication focus on achieving energy efficiency and reliability. Relay selection strategy for cooperative communication improves the performance significantly. However, due to imbalance consumption of power, network might die earlier and more than 90% energy remains unused. In this paper, we provide a framework of an energy-efficient medium access control protocol that minimizes these problems and improves energy efficiency.