• International journal of advanced smart convergence
• /
• 제7권4호
• /
• pp.92-100
• /
• 2018

This paper presents a link adaptation scheme for adaptive full duplex (AFD) systems. The signal modulation levels and communication link patterns are adaptively selected according to the changing channel conditions. The link pattern selection process consists of two successive steps such as a transmit-receive antenna pair selection based on maximum sum rate or minimum maximum symbol error rate, and an adaptive modulation based on maximum minimum norm. In AFD systems, the antennas of both nodes are jointly determined with modulation levels depending on the channel conditions. An adaptive algorithm with relatively low complexity is also proposed to select the link parameters. Simulation results show that the proposed AFD system offers significant bit error rate (BER) performance improvement compared with conventional full duplex systems with perfect or imperfect self-interference cancellation under the same fixed sum rate.

• Journal of Communications and Networks
• /
• 제17권2호
• /
• pp.162-171
• /
• 2015

This paper provides an analytic performance evaluation of the bit error rate (BER) of underlay decode-and-forward cognitive networks with best relay selection over Rayleigh multipath fading channels. A generalized BER expression valid for arbitrary operational parameters is firstly presented in the form of a single integral, which is then employed for determining the diversity order and coding gain for different best relay selection scenarios. Furthermore, a novel and highly accurate closed-form approximate BER expression is derived for the specific case where relays are located relatively close to each other. The presented results are rather convenient to handle both analytically and numerically, while they are shown to be in good agreement with results from respective computer simulations. In addition, it is shown that as in the case of conventional relaying networks, the behaviour of underlay relaying cognitive networks with best relay selection depends significantly on the number of involved relays.

• 한국통신학회논문지
• /
• 제36권5A호
• /
• pp.457-463
• /
• 2011

본 논문에서는 다중 셀 환경에서의 부분공간 간섭 정렬에서 레퍼런스 벡터간의 직교성을 통해 여러 개의 직교 레퍼런스 벡터 조합을 제공함으로써 전체 생의 합 용량이 최대화되도록 레퍼런스 벡터를 선정하는 방법을 제안하였다. 제안된 방법은 전체 셀의 채널용량을 최대화시키는 하나의 벡터를 선정하고 나머지 셀에서는 선택된 레퍼런스 벡터와 직교하는 벡터를 생성하여 채널 용량이 가장 큰 벡터를 각 셀의 레퍼런스 벡터로 선정한다. 제안된 방법은 주어진 채널에 적합한 레퍼런스 벡터를 선정 시 선택의 자유도를 높임으로써 기존보다 전체 셀 전송 용량을 증가시킨다. 전산 모의 실험을 통해 기존의 방법에 비해 높은 셀의 합용량 증대 성능을 보였다.

• 한국지능시스템학회논문지
• /
• 제6권2호
• /
• pp.52-56
• /
• 1996

신경망을 학습하는데 있어서, 망의 학습속도는 학습율에 의해 크게 좌우된다. 그러나 대부분의 정적인 학습율 선택 방법들은 몇몇 결정적인 방법들을 제외하곤 경험적인 방식에 의존해 왔다. 경험적인 방식을 사용하여 좋은 학습율을 찾아내는 것은 배우 지류하고 어려운 일이다. 또한 결정적인 방법들은 학습율의 질을 보장하지는 못한다. 본 논문에서 우리는 새로운 학습율 선택 방법을 제안한다. 우리의 방법은 진화 프로그래밍기법을 사용하여 통계적인 방식으로 접근함으로써 좋은 학습율을 찾을 수 있다. 모의 실험을 통하여 우리의 방식이 경험적인 방식들이나 결정적인 방식보다 우수함을 보였다.

• 한국정보통신학회논문지
• /
• 제18권1호
• /
• pp.42-49
• /
• 2014

듀얼 홉 시스템에서 기존의 두 홉에 대한 채널 정보를 이용하여 가장 좋은 성능을 나타내는 중계 노드 선택 기법은 채널 피드백을 위한 자원의 소모가 크다. 본 논문에서는 듀얼 홉 디코딩 후 전달 중계 시스템에서 첫 번째 홉에 대한 채널 정보만을 필요로 하는 부분 중계 노드 선택 기법을 이용하여 정확한 평균 비트 오차율을 분석한다. 이 때, 독립적인 레일레이 페이딩 채널을 가정하여 M-ary QAM에 대한 정확한 비트 오차율의 표현식을 유도한다. 또한, 수치적 결과를 통해 두 홉에 대한 채널 정보를 이용하여 가장 좋은 성능을 나타내는 중계 노드 선택 기법과 부분 중계 노드 선택 기법에 대한 성능을 비교한다. 여기서, 중계 노드의 수와 첫 번째 홉과 두 번째 홉 간 평균 채널 전력비를 다양하게 가정하여 평균 비트 오차율을 분석한다.

• 한국경영과학회지
• /
• 제41권3호
• /
• pp.1-21
• /
• 2016

The Markowitz portfolio selection model uses estimators to deduce input parameters. However, the estimation errors of input parameters negatively influence the performance of portfolios. Therefore, this model cannot be reliably applied to real-world investments. To overcome this problem, we suggest an algorithm that can exclude stocks with large estimation error from the portfolio by applying a tracking signal to the Markowitz portfolio selection model. By calculating the tracking signal of each stock, we can monitor whether unexpected departures occur on the outcomes of the forecasts on rate of returns. Thereafter, unreliable stocks are removed. By using this approach, portfolios can comprise relatively reliable stocks that have comparatively small estimation errors. To evaluate the performance of the proposed approach, a 10-year investment experiment was conducted using historical stock returns data from 6 different stock markets around the world. Performance was assessed and compared by the Markowitz portfolio selection model with additional constraints and other benchmarks such as minimum variance portfolio and the index of each stock market. Results showed that a portfolio using the proposed approach exhibited a better Sharpe ratio and rate of return than other benchmarks.

• Asian-Australasian Journal of Animal Sciences
• /
• 제21권11호
• /
• pp.1559-1571
• /
• 2008

A rule was developed to constrain the annual rate of inbreeding to a predefined value in a population with different lifetimes between sires and dams, and to maximize the selection response over generations. This rule considers that the animals in a population should be divided into sex-age classes based on the theory of gene flow, and restricts the increase of average inbreeding coefficient for new offspring by limiting the increase of the mean additive genetic relationship for parents selected. The optimization problem of this rule was formulated as a quadratic programming problem. Inputs for the rule were the BLUP estimated breeding values, the additive genetic relationship matrix of all animals, and the long-term contributions of sex-age classes. Outputs were optimal number and contributions of selected animals. In addition, this rule was combined with the optimization of emphasis given to QTL, and further increased the genetic gain over the planning horizon. Stochastic simulations of closed nucleus schemes for pigs were used to investigate the potential advantages obtained from this rule by combining the standard QTL selection, optimal QTL selection and conventional BLUP selection. Results showed that the predefined rates of inbreeding were actually achieved by this rule in three selection strategies. The rule obtained up to 9.23% extra genetic gain over truncation selection at the same rates of inbreeding. The combination of the extended rule and the optimization of emphasis given to QTL allowed substantial increases in selection response at a fixed annual rate of inbreeding, and solved substantially the conflict between short-term and long-term selection response in QTL-assisted selection schemes.

• Journal of Information Processing Systems
• /
• 제9권1호
• /
• pp.31-40
• /
• 2013

In this paper, a novel method is proposed to build an ensemble of classifiers by using a feature selection schema. The feature selection schema identifies the best feature sets that affect the arrhythmia classification. Firstly, a number of feature subsets are extracted by applying the feature selection schema to the original dataset. Then classification models are built by using the each feature subset. Finally, we combine the classification models by adopting a voting approach to form a classification ensemble. The voting approach in our method involves both classification error rate and feature selection rate to calculate the score of the each classifier in the ensemble. In our method, the feature selection rate depends on the extracting order of the feature subsets. In the experiment, we applied our method to arrhythmia dataset and generated three top disjointed feature sets. We then built three classifiers based on the top-three feature subsets and formed the classifier ensemble by using the voting approach. Our method can improve the classification accuracy in high dimensional dataset. The performance of each classifier and the performance of their ensemble were higher than the performance of the classifier that was based on whole feature space of the dataset. The classification performance was improved and a more stable classification model could be constructed with the proposed approach.

• 한국통신학회논문지
• /
• 제30권6C호
• /
• pp.560-569
• /
• 2005

본 논문은 순차적인 간섭제거와 전송 안테나 별 전송률을 제어하는 공간 다중화 전송 MIMO 시스템에서 채널환경에 따라 전송에 사용되는 안테나를 선택하고 데이터 율을 조절하는 알고리즘을 제안한다. 수신기에서 전송에 사용될 송신 안테나 및 전송률을 결정하고, 이는 각 송신 안테나 별 전송률에 대한 피드백 채널을 통해 송신기로 전송된다. 본 연구에서는 각 단계에서 최소의 SINR을 가지는 안테나를 제거해가는 연속적인 단계들로 이루어진 직렬 결정 방식을 제안한다. 또한, 각 연속적인 심볼 추정 단계에서 가장 낮은 신호 대 간섭 비를 갖는 심볼을 먼저 추정하는 "reverse detection ordering"이 각 안테나에 할당되는 용량 차이를 증가시킴으로서 안테나 선택에 의한 이득을 증가시킴을 보인다. 시뮬레이션 결과는 제안된 "reverse detection ordering"을 기반으로 하는 직렬 결정 방식이 낮은 복잡도을 가지면서 heuristic 방식과 비슷한 용량을 제공함을 보여준다.

• 디지털산업정보학회논문지
• /
• 제14권3호
• /
• pp.77-85
• /
• 2018

Multi-User Multiple-Input Multiple-Output (MU-MIMO) is the core technology for improving the channel capacity compared to Single-User MIMO (SU-MIMO) by using multiuser gain and spatial diversity. Key problem for the MU-MIMO is the user selection which is the grouping the users optimally. To solve this problem, we adopt Extreme Value Theory (EVT) at the beginning of the proposed algorithm, which defines a primary user set instead of a single user that has maximum channel power according to a predetermined threshold. Each user in the primary set is then paired with all of the users in the system to define user groups. By comparing these user groups, the group that produces a maximum sum rate can be determined. Through computer simulations, we have found that the proposed method outperforms the conventional technique yielding a sum rate that is 0.81 bps/Hz higher when the transmit signal to noise ratio (SNR) is 30 dB and the total number of users is 100.