The Poisson point process(PPP) has been widely used in wireless network modeling and performance analysis due to the independence between its nodes. Therefore, it may not be a suitable model for many of the exclusive ...The Poisson point process(PPP) has been widely used in wireless network modeling and performance analysis due to the independence between its nodes. Therefore, it may not be a suitable model for many of the exclusive networks between the nodes. This paper analyzes the energy efficiency(EE) and optimizes the two-tier heterogeneous cellular networks(Het Nets). Considering the mutual exclusion between macro base stations(MBSs) distribution, the deployment of MBSs is modeled by the Matérn hard-core point process(MHCPP), and the deployment of pico base stations(PBSs) is modeled by the PPP. We adopt a simple approximation method to study the signal to interference ratio(SIR) distribution in two-tier MHCPP-PPP networks and then derive the coverage probabilities, the average data rates and the energy efficiency of Het Nets. Finally, an optimization algorithm is proposed to improve the EE of Het Nets by controlling the transmit power of PBSs. The simulation results show that the EE of a system can be effectively improved by selecting the appropriate transmit power for the PBSs. In addition, two-tier MHCPP-PPP Het Nets have higher energy efficiency than two-tier PPP-PPP Het Nets.展开更多
Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-cover...Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.展开更多
We investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting ferrnions, in optical lattices by means of the perturb...We investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting ferrnions, in optical lattices by means of the perturbation expansion and Bogoliubov approach. The results show that the energy spectrum has a single band structure, and the energy is lower near zero momentum; the excitation spectrum gives corresponding energy gap, and the system is in Mort-insulating state at Tonks limit. The analytic result of energy spectrum is in good agreement with that calculated in terms of Green＇s function at strong correlation limit.展开更多
In this work,we theoretically study hard-core bosons on a two-dimensional square optical superlattice at T = 0.First of all,we present the mean field phase diagram of this model in terms of the chemical potential μ a...In this work,we theoretically study hard-core bosons on a two-dimensional square optical superlattice at T = 0.First of all,we present the mean field phase diagram of this model in terms of the chemical potential μ and the alternating potential strength △.Besides a superfluid(SF) phase at △ = 0 and a charge density wave(CDW)phase in the large △ at half filling,we demonstrate that a supersolid(SS) phase emerges in the moderate △.Then,we focus on the μ = 0,e.g.,half filling case,using large-S semi-classical spin-wave approximation to study the SS to CDW quantum phase transition.In particular,we calculate the ground-state energy and the superfluid density at the level of1/S correction.We then compare the spin-wave results with the large scale quantum Monte Carlo(QMC) simulations using the cluster stochastic series expansion(CSSE) algorithm,and find that while the spin wave method is intuitive with clear physical pictures,the quantum critical point is quite different from that of numerical results which is believed to be accurate.We suggest that as simple as it is,this model still exhibits strong quantum fluctuations near the quantum critical point beyond the power of semiclassical spin-wave approach.展开更多
Colloid-colloid interactions in charge-stabilized dispersions can to The crystallization process and polymorph selection of hard-core some extent be represented by the hard-core Yukawa model. Yukawa model are studied ...Colloid-colloid interactions in charge-stabilized dispersions can to The crystallization process and polymorph selection of hard-core some extent be represented by the hard-core Yukawa model. Yukawa model are studied by means of smart Monte Carlo simulations in the region of face-centered-cubic （fcc） phase. The contact value of bard-core Yukawa potential and the volume fraction of the colloids are fixed, while the Debye screening length can be varied. In the early stage of the crystallization, the precursors with relatively ordered liquid structure have been observed. Although the crystal structure of thermodynamically stable phase is fcc, the system crystallizes into a mixture of fcc and hexagonal close-packed （hcp） structures under small Debye screening length since the colloidal particles act as effective hard spheres. In the intermediate range of Debye screening length, the system crystallizes into a mixture of fcc, hcp, and body-centered-cubic （bcc）. The existence of metastable hcp and bcc structures can be interpreted as a manifestation of the Ostwald＇s step rule. Until the Debye screening length is large enough, the crystal structure obtained is almost a complete fcc suggesting the system eventually reaches to a thermodynamically stable state.展开更多
在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(M...在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(Matern Hard Core Point Processes,MHCPP)对ISAC基站的位置分布进行建模,考虑通信和感知时分复用的系统机制,以典型用户作为研究对象,将其关联到距离最近的基站,分别对通信和感知进行性能指标建模,推导典型用户和关联基站受到的平均干扰功率以及平均吞吐量的下界,并进一步通过仿真验证推导结果的准确性.仿真结果表明:相较于泊松点过程(Poisson Point Processes,PPP),MHCPP对平均干扰功率具有降低效果,通信场景中平均干扰功率降低了30%~43%,感知场景中平均干扰功率降低了91%~93%;随着基站间最小距离的增大,通信平均吞吐量增加,感知平均吞吐量先增后减,在实际场景中需结合系统需求来确定ISAC组网的参数设计.研究结果可为系统设计和扩展性分析提供参考.展开更多
广义Matern硬核点过程(Generalized Matern Hard-Core Point Process,GMHCPP)是在硬核点过程的基础上通过引入竞争函数和删减函数来限制保留概率的一种排斥点过程。针对两层异构蜂窝网络模型中宏基站与微基站的性能进行了深入研究,获得...广义Matern硬核点过程(Generalized Matern Hard-Core Point Process,GMHCPP)是在硬核点过程的基础上通过引入竞争函数和删减函数来限制保留概率的一种排斥点过程。针对两层异构蜂窝网络模型中宏基站与微基站的性能进行了深入研究,获得了该模型的覆盖概率和平均可达速率的近似表达式。首先,基于宏基站的性能差异及其排斥性生成保留概率函数,进而,将宏基站的部署以GMHCPP建模。然后,采用蒙特卡罗模拟方法对基站分布进行仿真,并绘制出了平均干扰信号比与路径损耗因子的关系图,根据该函数图,拟合得到了用泊松点过程近似时GMHCPP的增益因子表达式。最后,将增益因子代入覆盖概率和平均可达速率公式,对两层异构蜂窝网络模型的性能指标进行了仿真与分析。展开更多
基金partly supported by the National Natural Science Foundation of China(Grant No.61871241,No.61701221)the Natural Science Foundation of Jiangsu Province(No.BK20160781)+1 种基金Nantong Science and Technology Project(No.JC2018127,No.JC2019117)the Research Innovation Project for College Graduates of Jiangsu Province(No.KYLX16_0662)。
文摘The Poisson point process(PPP) has been widely used in wireless network modeling and performance analysis due to the independence between its nodes. Therefore, it may not be a suitable model for many of the exclusive networks between the nodes. This paper analyzes the energy efficiency(EE) and optimizes the two-tier heterogeneous cellular networks(Het Nets). Considering the mutual exclusion between macro base stations(MBSs) distribution, the deployment of MBSs is modeled by the Matérn hard-core point process(MHCPP), and the deployment of pico base stations(PBSs) is modeled by the PPP. We adopt a simple approximation method to study the signal to interference ratio(SIR) distribution in two-tier MHCPP-PPP networks and then derive the coverage probabilities, the average data rates and the energy efficiency of Het Nets. Finally, an optimization algorithm is proposed to improve the EE of Het Nets by controlling the transmit power of PBSs. The simulation results show that the EE of a system can be effectively improved by selecting the appropriate transmit power for the PBSs. In addition, two-tier MHCPP-PPP Het Nets have higher energy efficiency than two-tier PPP-PPP Het Nets.
基金supported by the National Science Foundation of China under Grant 61271186
文摘Sensing coverage is a fundamental design issue in wireless sensor networks(WSNs),while sensor scheduling ensures coverage degree to the monitored event and extends the network lifetime.In this paper,we address k-coverage scheduling problem in dense WSNs,we maintain a connected k-coverage energy efficiently through a novel Hard-Core based Coordinated Scheduling(HCCS),in which hardcore is a thinning process in stochastic geometry that inhibits more than one active sensor covering any area redundantly in a minimum distance. As compared with existing coordinated scheduling,HCCS allows coordination between sensors with little communication overhead.Moreover,due to the traditional sensing models in k-coverage analysis is unsuitable to describe the characteristic of transmit channel in dense WSNs,we propose a novel sensing model integrating Rayleigh Fading and Distribution of Active sensors(RFDA),and derive the coverage measure and k-coverage probability for the monitored event under RFDA. In addition,we analyze the influence factors,i.e. the transmit condition and monitoring degree to the k-coverage probability. Finally,through Monte Carlo simulations,it is shown that the k-coverage probability of HCCS outperforms that of its random scheduling counterpart.
文摘We investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting ferrnions, in optical lattices by means of the perturbation expansion and Bogoliubov approach. The results show that the energy spectrum has a single band structure, and the energy is lower near zero momentum; the excitation spectrum gives corresponding energy gap, and the system is in Mort-insulating state at Tonks limit. The analytic result of energy spectrum is in good agreement with that calculated in terms of Green＇s function at strong correlation limit.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10904096,10604024,11474025the Natural Science Foundation of Beijing under Grant No.1092009
文摘In this work,we theoretically study hard-core bosons on a two-dimensional square optical superlattice at T = 0.First of all,we present the mean field phase diagram of this model in terms of the chemical potential μ and the alternating potential strength △.Besides a superfluid(SF) phase at △ = 0 and a charge density wave(CDW)phase in the large △ at half filling,we demonstrate that a supersolid(SS) phase emerges in the moderate △.Then,we focus on the μ = 0,e.g.,half filling case,using large-S semi-classical spin-wave approximation to study the SS to CDW quantum phase transition.In particular,we calculate the ground-state energy and the superfluid density at the level of1/S correction.We then compare the spin-wave results with the large scale quantum Monte Carlo(QMC) simulations using the cluster stochastic series expansion(CSSE) algorithm,and find that while the spin wave method is intuitive with clear physical pictures,the quantum critical point is quite different from that of numerical results which is believed to be accurate.We suggest that as simple as it is,this model still exhibits strong quantum fluctuations near the quantum critical point beyond the power of semiclassical spin-wave approach.
基金the National Natural Science Foundation of China (11172302, 11302226, 10972217)the Opening Fund of State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, China (LNM201503)
文摘Colloid-colloid interactions in charge-stabilized dispersions can to The crystallization process and polymorph selection of hard-core some extent be represented by the hard-core Yukawa model. Yukawa model are studied by means of smart Monte Carlo simulations in the region of face-centered-cubic （fcc） phase. The contact value of bard-core Yukawa potential and the volume fraction of the colloids are fixed, while the Debye screening length can be varied. In the early stage of the crystallization, the precursors with relatively ordered liquid structure have been observed. Although the crystal structure of thermodynamically stable phase is fcc, the system crystallizes into a mixture of fcc and hexagonal close-packed （hcp） structures under small Debye screening length since the colloidal particles act as effective hard spheres. In the intermediate range of Debye screening length, the system crystallizes into a mixture of fcc, hcp, and body-centered-cubic （bcc）. The existence of metastable hcp and bcc structures can be interpreted as a manifestation of the Ostwald＇s step rule. Until the Debye screening length is large enough, the crystal structure obtained is almost a complete fcc suggesting the system eventually reaches to a thermodynamically stable state.
文摘在通感一体化(Integrated Sensing And Communication,ISAC)网络中,组网设计决定着通信和感知的性能.为给系统设计提供一般性的参考,利用随机几何(Stochastic Geometry,SG)从网络层面对组网设计进行数学建模和性能分析.基于硬核点过程(Matern Hard Core Point Processes,MHCPP)对ISAC基站的位置分布进行建模,考虑通信和感知时分复用的系统机制,以典型用户作为研究对象,将其关联到距离最近的基站,分别对通信和感知进行性能指标建模,推导典型用户和关联基站受到的平均干扰功率以及平均吞吐量的下界,并进一步通过仿真验证推导结果的准确性.仿真结果表明:相较于泊松点过程(Poisson Point Processes,PPP),MHCPP对平均干扰功率具有降低效果,通信场景中平均干扰功率降低了30%~43%,感知场景中平均干扰功率降低了91%~93%;随着基站间最小距离的增大,通信平均吞吐量增加,感知平均吞吐量先增后减,在实际场景中需结合系统需求来确定ISAC组网的参数设计.研究结果可为系统设计和扩展性分析提供参考.
文摘广义Matern硬核点过程(Generalized Matern Hard-Core Point Process,GMHCPP)是在硬核点过程的基础上通过引入竞争函数和删减函数来限制保留概率的一种排斥点过程。针对两层异构蜂窝网络模型中宏基站与微基站的性能进行了深入研究,获得了该模型的覆盖概率和平均可达速率的近似表达式。首先,基于宏基站的性能差异及其排斥性生成保留概率函数,进而,将宏基站的部署以GMHCPP建模。然后,采用蒙特卡罗模拟方法对基站分布进行仿真,并绘制出了平均干扰信号比与路径损耗因子的关系图,根据该函数图,拟合得到了用泊松点过程近似时GMHCPP的增益因子表达式。最后,将增益因子代入覆盖概率和平均可达速率公式,对两层异构蜂窝网络模型的性能指标进行了仿真与分析。
