针对高速铁路快速移动所引起的高多普勒频移进而可实现速率受限的问题,基于时延分多址和多普勒分多址技术,提出了高铁场景多用户上行链路的正交时频空间(orthogonal time frequency space,OTFS)多址传输方案。首先,基于高铁场景建立OTF...针对高速铁路快速移动所引起的高多普勒频移进而可实现速率受限的问题,基于时延分多址和多普勒分多址技术,提出了高铁场景多用户上行链路的正交时频空间(orthogonal time frequency space,OTFS)多址传输方案。首先,基于高铁场景建立OTFS多址的多用户系统模型;其次,在基站处将串行干扰消除应用于上行链路传输,利用多用户之间的信号差异消除干扰,实现对用户信号的正确检测;最后,根据互信息定理和迹运算的性质推导可实现速率的闭式表达式。仿真结果表明,相比于传统的多址传输方案,所提方案能更好地进行资源分配和抵抗多普勒频移,满足高速场景下车地通信上行传输的可实现速率需求。展开更多
In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to...In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.展开更多
In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buri...In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.展开更多
针对目前物理层安全研究大多未考虑信道估计误差对安全性能的影响,研究基于非理想信道状态信息(Channel State Information,CSI)的全双工双向中继网络安全性能。假设系统中用户之间没有直连链路,且无法获取CSI;采用最优中继选择方案,选...针对目前物理层安全研究大多未考虑信道估计误差对安全性能的影响,研究基于非理想信道状态信息(Channel State Information,CSI)的全双工双向中继网络安全性能。假设系统中用户之间没有直连链路,且无法获取CSI;采用最优中继选择方案,选取最优中继将信号进行解码转发至目的端;根据最大最小原则推导出系统安全容量和保密中断概率(Secrecy Outage Probability,SOP)的表达式,进一步分析影响系统保密性能的主要因素,并对比全双工与半双工系统性能的差异。仿真结果表明,当中继节点处在用户间的中点位置时,系统保密性能最好;同时,减小信道估计误差、窃听链路的平均信噪比及剩余自干扰能够有效降低系统SOP,适当地增加中继数目可以获得更好的安全性能。展开更多
文摘针对高速铁路快速移动所引起的高多普勒频移进而可实现速率受限的问题,基于时延分多址和多普勒分多址技术,提出了高铁场景多用户上行链路的正交时频空间(orthogonal time frequency space,OTFS)多址传输方案。首先,基于高铁场景建立OTFS多址的多用户系统模型;其次,在基站处将串行干扰消除应用于上行链路传输,利用多用户之间的信号差异消除干扰,实现对用户信号的正确检测;最后,根据互信息定理和迹运算的性质推导可实现速率的闭式表达式。仿真结果表明,相比于传统的多址传输方案,所提方案能更好地进行资源分配和抵抗多普勒频移,满足高速场景下车地通信上行传输的可实现速率需求。
基金supported in part by National Natural Science Foundation of China under Grant 62461024Jiangxi Provincial Natural Science Foundation of China under Grant 20224ACB202001.
文摘In high-speed railway(HSR)wireless communication,the rapid channel changes and limited high-capacity access cause significant impact on the link performance.Meanwhile,the Doppler shift caused by high mobility leads to the inter-carrier interference.In this paper,we propose a reconfigurable intelligent surface(RIS)-assisted receive spatial modulation(SM)scheme based on the spatial-temporal correlated HSR Rician channel.The characteristics of SM and the phase shift adjustment of RIS are used to mitigate the performance degradation in high mobility scenarios.Considering the influence of channel spatial-temporal correlation and Doppler shift,the effects of different parameters on average bit error rate(BER)performance and upper bound of ergodic capacity are analyzed.Therefore,a joint antenna and RIS-unit selection algorithm based on the antenna removal method is proposed to increase the capacity performance of communication links.Numerical results show that the proposed RIS-assisted receive SM scheme can maintain high transmission capacity compared to the conventional HSR-SM scheme,whereas the degradation of BER performance can be compensated by arranging a large number of RIS-units.In addition,selecting more RIS-units has better capacity performance than activating more antennas in the low signal-to-noise ratio regions.
基金the National Natural Science Foundation of China(Nos.41172290 and40572160)
文摘In order to evaluate the feasibility of safe mining close to the contact zone under reduced security coal pillar conditions at a coal mine in eastern China, the interaction mechanism of the interface between deep buried sand and a paleo-weathered rock mass was investigated in the laboratory by direct shear testing. A DRS-1 high pressure soil shear testing machine and orthogonal design method were used in the direct shear tests. Variance and range methods were applied to analyze the sensitivity of each factor that has an influence on the mechanical characters of the interface. The test results show that the normal pressure is the main influencing factor for mechanical characteristics of the interface, while the lithological characters and roughness are minor factors; the shear stress against shear displacement curve for the interface shows an overall hyperbola relationship, no obvious peak stress and dilatancy was observed.When the normal pressure is 6 MPa, the shear strengths of interfaces with different roughness are basically the same, and when the normal pressure is more than 8 MPa, the larger the roughness of the interface, the larger will be the shear strength; the shear strength has a better linear relationship with the normal pressure, which can be described by a linear Mohr–Coulomb criterion.
文摘针对目前物理层安全研究大多未考虑信道估计误差对安全性能的影响,研究基于非理想信道状态信息(Channel State Information,CSI)的全双工双向中继网络安全性能。假设系统中用户之间没有直连链路,且无法获取CSI;采用最优中继选择方案,选取最优中继将信号进行解码转发至目的端;根据最大最小原则推导出系统安全容量和保密中断概率(Secrecy Outage Probability,SOP)的表达式,进一步分析影响系统保密性能的主要因素,并对比全双工与半双工系统性能的差异。仿真结果表明,当中继节点处在用户间的中点位置时,系统保密性能最好;同时,减小信道估计误差、窃听链路的平均信噪比及剩余自干扰能够有效降低系统SOP,适当地增加中继数目可以获得更好的安全性能。
