Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies,spectrum handoff can guarantee the transmission continuity of secondary users(SUs). In this paper,we...Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies,spectrum handoff can guarantee the transmission continuity of secondary users(SUs). In this paper,we address a new and more generalized spectrum handoff problem in cognitive radio networks(CRNs),by considering simultaneously energy efficiency,multiple spectrum handoffs and multiple channels. Furthermore,effects of the primary users'(PUs')arrival and service rate on the target channel sequence selection are also considered. In order to obtain the energy-efficient target channel sequence,we firstly analyze the energy consumption and the number of delivered bits per hertz in the spectrum handoff process,and formulate a ratio-type energy efficiency optimization problem,which can be transformed into a parametric problem by utilizing fractional programming. Then,we propose an algorithm combining dynamic programming with bisection(DPB)algorithm to solve the energy efficiency optimization problem. Our simulation results verify that the designed target channel sequence has better performance than the existing algorithms in terms of energy efficiency.展开更多
The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes i...The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes is time-varied due to primary user/secondary user(PU/SU) activity and mobility, which result in non-determinacy. This paper studies the spectrum allocation for CRNs with non-deterministic bandwidth of spectrum holes. We present a novel probability density function(PDF) through order statistics as well as its simplified form to describe the statistical properties of spectrum holes, with which a statistical spectrum allocation model based on stochastic multiple knapsack problem(MKP) is formulated for spectrum allocation with non-deterministic bandwidth of spectrum holes. To reduce the computational complexity, we transform this stochastic programming problem into a constant MKP through exploiting the properties of cumulative distribution function(CDF), which can be solved via MTHG algorithm by using auxiliary variables. Simulation results illustrate that the proposed statistical spectrum allocation algorithm can achieve better performance compared with the existing algorithms when the bandwidth of spectrum holes is time-varied.展开更多
Over the past few decades, the world has witnessed a rapid growth in mobile and wireless networks（MWNs） which significantly change human life. However, proliferating mobile demands lead to several intractable challe...Over the past few decades, the world has witnessed a rapid growth in mobile and wireless networks（MWNs） which significantly change human life. However, proliferating mobile demands lead to several intractable challenges that MWN has to face. Software-defined network is expected as a promising way for future network and has captured growing attention. Network virtualization is an essential feature in software-defined wireless network（SDWN）, and it brings two new entities, physical networks and virtual networks. Accordingly, efficiently assigning spectrum resource to virtual networks is one of the fundamental problems in SDWN. Directly orienting towards the spectrum resource allocation problem, firstly, the fluctuation features of virtual network requirements in SDWN are researched, and the opportunistic spectrum sharing method is introduced to SDWN. Then, the problem is proved as NP-hardness. After that, a dynamic programming and graph theory based spectrum sharing algorithm is proposed.Simulations demonstrate that the opportunistic spectrum sharing method conspicuously improves the system performance up to around 20%–30% in SDWN, and the proposed algorithm achieves more efficient performance.展开更多
提出多载荷时间历程的外推方法,给出车下设备承载结构疲劳试验载荷谱编制方法。基于载荷时间历程的雨流计数矩阵,利用二维核密度估计方法(Kernel density estimation,KDE),提出在多载荷时间历程输入条件下的外推方法;应用平均应力修正...提出多载荷时间历程的外推方法,给出车下设备承载结构疲劳试验载荷谱编制方法。基于载荷时间历程的雨流计数矩阵,利用二维核密度估计方法(Kernel density estimation,KDE),提出在多载荷时间历程输入条件下的外推方法;应用平均应力修正公式、累积损伤理论和等效损伤准则,根据外推载荷数据,给出疲劳试验程序谱的编制方法;结合动车组车下设备线路测试数据对外推方法进行验证,编制了车下设备承载结构疲劳试验程序谱,并分别使用疲劳试验程序谱和振动测试数据对承载结构进行疲劳强度计算。数据外推结果表明:多载荷时间历程外推方法计算的损伤与实际载荷损伤误差为3.6%,大的扩展倍数下KDE可以给出低周、大幅值载荷;疲劳强度计算结果表明:由于KDE外推产生了大幅值载荷,疲劳试验程序谱计算的损伤比振动测试数据计算的损伤增加了43.8%,所以,在进行疲劳试验载荷谱编制时,需要计算可能出现的大幅值载荷。此研究为其他结构程序载荷谱的编制提供借鉴案例。展开更多
基金Heilongjiang Province Natural Science Foundation(Grant No.F2016019)；National Natural Science Foundation of China(Grant No.61571162)；Major National Science and Technology Project(2015ZX03004002004)； China Postdoctoral Science Foundation(Grant No.2014M561347).
文摘Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies,spectrum handoff can guarantee the transmission continuity of secondary users(SUs). In this paper,we address a new and more generalized spectrum handoff problem in cognitive radio networks(CRNs),by considering simultaneously energy efficiency,multiple spectrum handoffs and multiple channels. Furthermore,effects of the primary users'(PUs')arrival and service rate on the target channel sequence selection are also considered. In order to obtain the energy-efficient target channel sequence,we firstly analyze the energy consumption and the number of delivered bits per hertz in the spectrum handoff process,and formulate a ratio-type energy efficiency optimization problem,which can be transformed into a parametric problem by utilizing fractional programming. Then,we propose an algorithm combining dynamic programming with bisection(DPB)algorithm to solve the energy efficiency optimization problem. Our simulation results verify that the designed target channel sequence has better performance than the existing algorithms in terms of energy efficiency.
基金supported by the National Natural Science Foundation of China (No.61501065, 91438104,No.61571069 and No.61601067)the Fundamental Research Funds for the Central Universities (No.106112015CDJXY160002,No.106112016CDJXY160001)the Chongqing Research Program of Basic Research and Frontier Technology (No.CSTC2016JCYJA0021)
文摘The spectrum allocation for cognitive radio networks(CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes is time-varied due to primary user/secondary user(PU/SU) activity and mobility, which result in non-determinacy. This paper studies the spectrum allocation for CRNs with non-deterministic bandwidth of spectrum holes. We present a novel probability density function(PDF) through order statistics as well as its simplified form to describe the statistical properties of spectrum holes, with which a statistical spectrum allocation model based on stochastic multiple knapsack problem(MKP) is formulated for spectrum allocation with non-deterministic bandwidth of spectrum holes. To reduce the computational complexity, we transform this stochastic programming problem into a constant MKP through exploiting the properties of cumulative distribution function(CDF), which can be solved via MTHG algorithm by using auxiliary variables. Simulation results illustrate that the proposed statistical spectrum allocation algorithm can achieve better performance compared with the existing algorithms when the bandwidth of spectrum holes is time-varied.
基金supported by the National Natural Science Foundation of China(6102100161133015+4 种基金61171065)the National Natural Science Foundation of China(973 Program)(2013CB329001)the National High Technology ResearchDevelopment Program(863 Program)(2013AA0106052013AA013500)
文摘Over the past few decades, the world has witnessed a rapid growth in mobile and wireless networks（MWNs） which significantly change human life. However, proliferating mobile demands lead to several intractable challenges that MWN has to face. Software-defined network is expected as a promising way for future network and has captured growing attention. Network virtualization is an essential feature in software-defined wireless network（SDWN）, and it brings two new entities, physical networks and virtual networks. Accordingly, efficiently assigning spectrum resource to virtual networks is one of the fundamental problems in SDWN. Directly orienting towards the spectrum resource allocation problem, firstly, the fluctuation features of virtual network requirements in SDWN are researched, and the opportunistic spectrum sharing method is introduced to SDWN. Then, the problem is proved as NP-hardness. After that, a dynamic programming and graph theory based spectrum sharing algorithm is proposed.Simulations demonstrate that the opportunistic spectrum sharing method conspicuously improves the system performance up to around 20%–30% in SDWN, and the proposed algorithm achieves more efficient performance.
文摘提出多载荷时间历程的外推方法,给出车下设备承载结构疲劳试验载荷谱编制方法。基于载荷时间历程的雨流计数矩阵,利用二维核密度估计方法(Kernel density estimation,KDE),提出在多载荷时间历程输入条件下的外推方法;应用平均应力修正公式、累积损伤理论和等效损伤准则,根据外推载荷数据,给出疲劳试验程序谱的编制方法;结合动车组车下设备线路测试数据对外推方法进行验证,编制了车下设备承载结构疲劳试验程序谱,并分别使用疲劳试验程序谱和振动测试数据对承载结构进行疲劳强度计算。数据外推结果表明:多载荷时间历程外推方法计算的损伤与实际载荷损伤误差为3.6%,大的扩展倍数下KDE可以给出低周、大幅值载荷;疲劳强度计算结果表明:由于KDE外推产生了大幅值载荷,疲劳试验程序谱计算的损伤比振动测试数据计算的损伤增加了43.8%,所以,在进行疲劳试验载荷谱编制时,需要计算可能出现的大幅值载荷。此研究为其他结构程序载荷谱的编制提供借鉴案例。
