• Journal of Communications and Networks
• /
• 제11권2호
• /
• pp.157-165
• /
• 2009

In this paper, we investigate a dynamic spectrum sharing problem for the centralized uplink cognitive radio networks using orthogonal frequency division multiple access. We formulate a large-scale joint rate and power allocation as an optimization problem under quality of service constraint for secondary users and interference constraint for primary users. We also suggest admission control to nd a feasible solution to the optimization problem. To implement the resource allocation on a large-scale, we introduce a notion of using the conservative factors $\alpha$ and $\beta$ depending on the outage and violation probabilities. Since estimating instantaneous channel gains is costly and requires high complexity, the proposed algorithm pursues a practical and implementation-friendly resource allocation. Simulation results demonstrate that the large-scale joint rate and power allocation incurs a slight loss in system throughput over the instantaneous one, but it achieves lower complexity with less sensitivity to variations in shadowing statistics.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권4호
• /
• pp.1471-1488
• /
• 2018

Interference mitigation is a significant issue in the cognitive heterogeneous networks, this paper studied how to reduce the interference to macrocell users (MU) and improve system throughput. Establish the interference model with imperfect spectrum sensing by analyzing the source of interference complexity. Based on the user topology, the optimize problem was built to maximize the downlink throughput under given interference constraint and the total power constraint. We decompose the resource allocation problem into subcarrier allocation and power allocation. In the subcarrier assignment step, the allocated number of subcarriers satisfies the requirement of the femtocell users (FU).Then, we designed the power allocation algorithm based on the Lagrange multiplier method and the improved water filling method. Simulation results and performance analyses show that the proposed algorithm causes less interference to MU than the algorithm without considering imperfect spectrum sensing, and the system achieves better throughput performance.

• 한국치위생학회지
• /
• 제15권3호
• /
• pp.371-377
• /
• 2015

Objectives: The purpose of the study was to investigate the relation between learning strategy and academic achievement in the dental hygiene students. Methods: A self-reported questionnaire was completed by 207 dental hygiene students in Gyeongnam from April 1 to 30, 2014. The questionnaire consisted fo 51 questions of learning strategy and 1 question of academic achievement. The data were analyzed using SPSS 17.0 program for descriptive analyses, t-test, Pearson correlation and multiple regressing analysis. Results: The organized strategy and learning time management had a significantly positive influence on high scores in the junior and senior students. Learning strategie(r=0.419) and cognitive strategies(r=0.343), metacognitive strategies(r=0.239), resource management strategies(r=0.415) had significantly positive correlation to academic achievement. Cognitive strategy of learning strategies(p<0.05) and resource management strategies(p<0.001) had a positive effect on higher academic achievement. Conclusions: The learning strategies will provide the dental hygiene students with active participations.

• ETRI Journal
• /
• 제44권3호
• /
• pp.400-412
• /
• 2022

In cognitive radio networks (CRNs), the computational complexity of resource allocation algorithms is a significant problem that must be addressed. However, the high computational complexity of the optimal solution for tackling resource allocation in CRNs makes it inappropriate for use in practical applications. Therefore, this study proposes a power-based pricing algorithm (PPA) primarily to reduce the computational complexity in downlink CRN scenarios while restricting the interference to primary users to permissible levels. A two-stage approach reduces the computational complexity of the proposed mathematical model. Stage 1 assigns subcarriers to the CRN's users, while the utility function in Stage 2 incorporates a pricing method to provide a power algorithm with enhanced reliability. The PPA's performance is simulated and tested for orthogonal frequency-division multiplexing-based CRNs. The results confirm that the proposed algorithm's performance is close to that of the optimal algorithm, albeit with lower computational complexity of O(M log(M)).

• 한국통신학회논문지
• /
• 제34권9A호
• /
• pp.697-703
• /
• 2009

인지무선 통신장치(cognitive radio)는 일반적으로 일차 사용자(primary user)와의 간섭을 피하기 위해 어떠한 일차 사용자도 점유하고 있지 않은 주파수 자원을 활용한다. 그러나 비어있는 주파수 자원을 발견할 수 없을 경우, 인지무선 통신장치는 언더레이(underlay) 형태로 일차 사용자들과 주파수를 공유할 수 있으며, 이 때 스스로의 통신이 일차 사용자들에게 간섭을 미치지 않도록 전송 전력을 조절해야 한다. 본 논문은 셀룰라 네트워크의 상향링크 주파수 자원을 사용하는 언더레이 주파수 공유 방법을 제안한다. 셀룰라 네트워크의 범위 안에 존재하는 한쌍의 인지무선 통신장치들이 단방향 점대점(point-to-point) 통신 링크를 생성할 때 사용할 수 있는 전송 전력의 재한을 계산하고, 계산된 전송 전력을 적용할 수 있는 실용적인 상향 링크 공유 방안을 제시한다. 또한 시뮬레이션을 통해 제안된 상향 링크 공유 방안이 하향 링크 주파수 자원을 공유하는 것에 비해 인지무선 통신장치의 부담(overhead)을 줄일 뿐만 아니라 점대점 통신 링크의 수율(throughput) 성능을 향상시킬 수 있음을 보인다.

• 대한가정학회지
• /
• 제33권6호
• /
• pp.137-148
• /
• 1995

The purpose of this study was to classify the cognitive management style of housewives, to explore the effect of demographic variables on the style, and to investigate satisfaction of resources such as money, time and energy, according to different styles. For this purpose, the samples of 355 housewives were collected in Seoul. And various analysis methods, such as frequencies, percentages, means, chi-square test and GLM, were employed. The results of this study were as follows ; 1) Among 355 respondents, systematic managers, analyzing managers, holistic managers and feeling managers were 103, 96, 82 and 74 respectively. 2) Depending on information gathering and evaluation, the style was influenced by wives' education, wives' employment status, and family life cycle. 3) By style, satisfaction of resource was differenciated significantly. Between money, time and energy resources, especially, satisfaction of energy resource had significant differences.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제9권11호
• /
• pp.4387-4404
• /
• 2015

The energy-efficient design of sensing-based spectrum sharing of a multi-input and multi-output (MIMO) cognitive radio (CR) system with imperfect multiple antenna spectrum sensing is investigated in this study. Optimal resource allocation strategies, including sensing time and power allocation schemes, are studied to maximize the energy efficiency (EE) of the secondary base station under the transmit power and interference power constraints. EE problem is formulated as a nonlinear stochastic fractional programming of a nonconvex optimal problem. The EE problem is transformed into its equivalent nonlinear parametric programming and solved by one-dimension search algorithm. To reduce searching complexity, the search range was founded by demonstration. Furthermore, simulation results confirms that an optimal sensing time exists to maximize EE, and shows that EE is affected by the spectrum detection factors and corresponding constraints.

• 대한인간공학회지
• /
• 제28권3호
• /
• pp.73-79
• /
• 2009

Driving is a complex psychomotor task often interrupted by secondary activities that increase cognitive workload and divert attention away from the roadway. The risk of inattentive driving is known to vary with age. To assess the characteristics of advancing age on driver's cognitive workload under dual task condition, we evaluate the performance of 96 drivers divided into three age groups: 20's, 40's, and 60's. This study considers driver's cognitive workload in the context of urban and highway driving. Error rate & Dual task cost are used to measure driver's cognitive workload. Results indicate that age impacts cognitive workload during dual task driving conditions.

• 한국통신학회논문지
• /
• 제33권11A호
• /
• pp.1013-1020
• /
• 2008

코그니티브 라디오(cognitive radio) 기술 중 같은 지역에서 코그니티브 사용자와 우선사용자가 주파수를 공유하여 사용하는 방법은 단위 지역 당 주파수 사용효율을 향상시킬 수 있는 중요한 기술로 인식되고 있다. 본 논문에서는 코그니티브 라디오 시스템이 우선사용자에게 간섭을 미치지 않으며 동일 지역에서 우선사용자와 주파수를 공유할 수 있는 직교 빔 형성 방법을 제안한다. 제안된 방법은 우선사용자의 채널상태정보(channel state information)로부터 얻어진 부공간에 직교하는 코그니티브 라디오 사용자를 위한 부공간을 형성함으로써 우선사용자에게 간섭을 주지 않으며 주파수를 공유할 수 있는 코그니티브 라디오 사용자를 위한 다중 빔을 생성한다. 그러고, 코그니티브 라디오 시스템의 합 용량을 증가시키기 위해 기회적 무선자원할당 기법을 적용하였다. 전산모의 실험을 통해 제안된 주파수 공유 방법이 우선사용자에게 간섭을 주지 않음을 보였고 코그니티브 라디오 기지국이 2개의 안테나를 사용할 경우 시스템 합용량이 일반 셀룰라 시스템의 빔 포밍을 적용한 결과와 유사하게 사용자 20명에서 최대 2.72bps/Hz를 얻을 수 있음을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권6호
• /
• pp.2873-2892
• /
• 2019

Reducing the interference to the licensed mobile users and obtaining the energy efficiency are key issues in cognitive heterogeneous networks. A corresponding rate loss constraint is proposed to be used for the sensing-based spectrum sharing (SBSS) model in cognitive heterogeneous networks in this paper. Resource allocation optimization strategy is designed for the maximum energy efficiency under the proposed interference constraint together with average transmission power constraint. An efficiency algorithm is studied to maximize energy efficiency due to the nonconvex optimal problem. Furthermore, the relationship between the proposed protection criterion and the conventional interference constraint strategy under imperfect sensing condition for the SBSS model is also investigated, and we found that the conventional interference threshold can be regarded as the upper bound of the maximum rate loss that the primary user could tolerate. Simulation results have shown the effectiveness of the proposed protection criterion overcome the conventional interference power constraint.