• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권12호
• /
• pp.5943-5962
• /
• 2017

A resource allocation algorithm based on simultaneous wireless information and power transfer (SWIPT) to maximize the system throughput is proposed in orthogonal frequency division multiplexing (OFDM) relay networks. The algorithm formulates the problem under the peak power constraints of the source and each subcarrier (SC), and the energy causality constraint of the relay. With the given SC allocation of the source, we give and prove the optimal propositions of the formulated problem. Then, the formulated problem could be decomposed into two separate throughput maximization sub-problems by setting the total power to transfer energy. Finally, several SC allocation schemes are proposed, which are energy priority scheme, information priority scheme, balanced allocation scheme and exhaustive scheme. The simulation results reveal that the energy priority scheme can significantly reduce computational complexity and achieve approximate performance with the exhaustive scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권5호
• /
• pp.2015-2028
• /
• 2016

In this paper, we propose a sum transmission rate maximization based cooperative spectrum sharing protocol with quality-of-service (QoS) support for both of the primary and secondary systems, which exploits the situation when the primary system experiences a weak channel. The secondary transmitter ST_b which provides the best performance for the primary and secondary systems is selected to forward the primary signal. Specifically, ST_b helps the primary system achieve the target rate by using a fraction of its power to forward the primary signal. As a reward, it can gain spectrum access by using the remaining power to transmit its own signal. We study the secondary user selection and optimal power allocation such that the sum transmission rate of primary and secondary systems is maximized, while the QoS of both primary and secondary systems can be guaranteed. Simulation results demonstrate the efficiency of the proposed spectrum sharing protocol and its benefit to both primary and secondary systems.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권12호
• /
• pp.5614-5633
• /
• 2018

Mobile Edge Computing (MEC) and Wireless Power Transfer (WPT) are both recognized as promising techniques, one is for solving the resource insufficient of mobile devices and the other is for powering the mobile device. Naturally, by integrating the two techniques, task will be capable of being executed by the harvested energy which makes it possible that less intrinsic energy consumption for task execution. However, this innovative integration is facing several challenges inevitably. In this paper, we aim at prolonging the battery life of mobile device for which we need to maximize the harvested energy and minimize the consumed energy simultaneously, which is formulated as residual energy maximization (REM) problem where the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device are all considered as key factors. To this end, we jointly optimize the offloading ratio, energy harvesting time, CPU frequency and transmission power of mobile device to solve the REM problem. Furthermore, we propose an efficient convex optimization and sequential unconstrained minimization technique based combining method to solve the formulated multi-constrained nonlinear optimization problem. The result shows that our joint optimization outperforms the single optimization on REM problem. Besides, the proposed algorithm is more efficiency.

• 지구물리와물리탐사
• /
• 제19권1호
• /
• pp.11-19
• /
• 2016

나머지 정적보정 기법중에서 가장 많이 쓰이는 주행시간 분해기법과 겹쌓기제곱 최대화기법의 적용성을 육상 탄성파자료에서 비교 검토하였다. 모든 발파점과 수신점에 대한 임의의 나머지 정적보정값(시간차이)과 무작위 잡음이 포함된 모델자료에서 겹쌓기제곱 최대화기법은 주행시간 분해기법에 비해 흐트러진 반사 이벤트를 정확히 정렬시키고 보정과정에서 출력된 발파점과 수신점의 정적보정 그래프가 입력된 값과 거의 같은 진폭으로 역전된다는 점에서 신호대잡음이 작은 자료의 반사면 향상에 보다 효과적이었다. 나머지 정적보정에 적합한 입력인자(최대허용 시간차이, 상관창, 반복횟수)들은 공통중간점 자료외에 공통발파점 겹쌓기자료와 공통수신점 겹쌓기자료에 대한 연속 테스트를 거쳐 효과적으로 진단할 수 있었다. 나머지 정적보정에 앞서 송수신점의 높이보정 및 풍화대 깊이보정을 실시하여 장파장 시간차이를 제거하고 진동수-파수 필터링, 예측곱풀기, 시간변화 빛띠흰색화로 잡음을 줄여 교차상관의 오차를 최소화시킨다. 또한 나머지 정적보정후 수직시간차 역보정을 거쳐 속도를 재분석하여 겹쌓기한 결과 저류층을 포함한 반사면들의 향상된 연속성 및 분해능을 확인할 수 있었다.

• 한국정보통신학회논문지
• /
• 제17권12호
• /
• pp.2826-2834
• /
• 2013

이동 애드혹 네트워크에서 단말의 전력절감과 관련된 기술은 송신전력제어(transmit power control; TPC), 전력절감모드(power-saving mode; PSM), 라우팅(routing)으로 나뉠 수 있다. TPC와 PSM은 주로 하위 물리 및 데이터링크 계층에서 담당하는 반면 라우팅은 상위 네트워크 계층에서 담당하므로 이들 알고리즘들이 하나의 목적을 위해 보다 나은 성능을 제공하기 위해서는 통합된 관점에서의 알고리즘 설계가 필요하다. 따라서 본 논문에서는 애드혹 네트워크에서 주어진 종단간 전송률을 만족시키면서 전송 경로의 생존시간을 최대화하는 것을 목적으로 전력절감과 라우팅의 결합 알고리즘을 제안한다. 제안 방안은 먼저 단말의 송신전력을 줄이기 위하여 TPC 또는 PSM을 적용하여 개별 단말의 생존시간을 증가시키고, 이후 결정된 노드 생존시간을 고려하여 라우팅을 수행함으로써 멀티홉 전체 경로의 생존시간을 극대화한다. 시뮬레이션 결과 제안방식은 네트워크의 단말 수 및 간섭량의 변화에 따라 요구 전송률을 만족시키면서 생존시간을 극대화시킨다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제15권6호
• /
• pp.2204-2224
• /
• 2021

This paper studies secure wireless transmission from a multi-antenna transmitter to a single-antenna intended receiver overheard by multiple eavesdroppers with considering the imperfect channel state information (CSI) of wiretap channel. To enhance security of communication link, the artificial noise (AN) is generated at transmitter. We first design the robust joint optimal beamforming of secret signal and AN to minimize transmit power with constraints of security quality of service (QoS), i.e., minimum allowable signal-to-interference-and-noise ratio (SINR) at receiver and maximum tolerable SINR at eavesdroppers. The formulated design problem is shown to be nonconvex and we transfer it into linear matrix inequalities (LMIs). The semidefinite relaxation (SDR) technique is used and the approximated method is proved to solve the original problem exactly. To verify the robustness and tightness of proposed beamforming, we also provide a method to calculate the worst-case SINR at eavesdroppers for a designed transmit scheme using semidefinite programming (SDP). Additionally, the secrecy rate maximization is explored for fixed total transmit power. To tackle the nonconvexity of original formulation, we develop an iterative approach employing sequential parametric convex approximation (SPCA). The simulation results illustrate that the proposed robust transmit schemes can effectively improve the transmit performance.

• Advances in Energy Research
• /
• 제1권2호
• /
• pp.97-106
• /
• 2013

This study designs and tests a photovoltaic system with distributed maximum power point tracking (DMPPT) methodology using a field programmable gate array (FPGA) controller. Each solar panel in the distributed PV system is equipped with a newly designed DC/DC converter and the panel's voltage output is regulated by a FPGA controller using PI control. Power from each solar panel on the system is optimized by another controller where the quadratic maximization MPPT algorithm is used to ensure the panel's output power is always maximized. Experiments are carried out at atmospheric insolation with partial shading conditions using 4 amorphous silicon thin film solar panels of 2 different grades fabricated by Chi-Mei Energy. It is found that distributed MPPT requires only 100ms to find the maximum power point of the system. Compared with the traditional centralized PV (CPV) system, the distributed PV (DPV) system harvests more than 4% of solar energy in atmospheric weather condition, and 22% in average under 19% partial shading of one solar panel in the system. Test results for a 1.84 kW rated system composed by 8 poly-Si PV panels using another DC/DC converter design also confirm that the proposed system can be easily implemented into a larger PV power system. Additionally, the use of NI sbRIO-9642 FPGA-based controller is capable of controlling over 16 sets of PV modules, and a number of controllers can cooperate via the network if needed.

• KIEE International Transactions on Power Engineering
• /
• 제5A권4호
• /
• pp.396-402
• /
• 2005

In an electricity market with imperfect competition, participants devise bidding plans and transaction strategies to maximize their own profits. The market price and the quantity are concerned with the operation reserve as well as the bidding system and demand curves in an electricity market. This paper presents a market model combined by an energy market and an operating reserve market. The competition of the generation producers in the combined market is formulated as a gaming of selecting bid parameters such as intersections and slopes in bid functions. The Nash Equilibrium (NE) is analyzed by using bi-level optimization; maximization of Social Welfare (SW) and maximization of the producers' profits.

• Journal of the Korean Data and Information Science Society
• /
• 제12권1호
• /
• pp.103-125
• /
• 2001

The Box-Cox transformation is a well known family of power transformation that brings a set of data into agreement with the normality assumption of the residuals and hence the response variable of a postulated model in regression analysis. This paper proposes a new method for estimating the Box-Cox transformation using maximization of the Sample Entropy statistic which forces the data to get closer to normal as much as possible. A comparative study of the proposed procedure with the maximum likelihood procedure, the procedure via artificial regression estimation, and the recently introduced maximization of the Shapiro-Francia W' statistic procedure is given. In addition, we generate a table for the optimal spacings parameter in computing the Sample Entropy statistic.

• Journal of electromagnetic engineering and science
• /
• 제19권1호
• /
• pp.31-36
• /
• 2019

In this study, an effective method for designing an electromagnetic multilayer radome is introduced. This method is achieved by using ant colony optimization for a continuous domain in the transmission coefficient maximization with stability for a wide angle of incidence in both perpendicular and parallel polarizations in specific X- and Ku-bands. To obtain the optimized parameter for a C-sandwich radome, particle swarm optimization algorithm is operated to give a clear comparison on the effectiveness of ant colony optimization for a continuous domain. The qualification of an optimized multilayer radome is also compared with an effective solid radome type in transmitted power stability and presented in this research.