Heterogeneous networks(HetNets)consisting of macro cells with very large antenna arrays and a secondary tier of small cells with a few antennas each can well tackle the contradiction of large coverage of the network a...Heterogeneous networks(HetNets)consisting of macro cells with very large antenna arrays and a secondary tier of small cells with a few antennas each can well tackle the contradiction of large coverage of the network and high data rate at the hot spots.However,it is not permissible to assign orthogonal pilot sequences for all the supported users due to the large number.Hence,we propose a pilot reduction scheme based on the heterogeneous system configurations and the unique topology of this HetNet.The reusing of pilot sequences causes the presence of the contaminated channel state information(CSI) and results in receivers' Quality of Service(QoS) outage.With the contaminated CSI,we provide an energy-efficient beamforming based on minimizing the total power consumption while keeping the QoS constraints satisfied and restricting the QoS outage probability below a given specification.By applying the approach of Bernstein approximation and semi-definite relaxation,we transform the original intractable chance constrained program to a convex problem conservatively.Numerical results show that the average power consumption of the proposed beamforming for our pilot reduction scheme is close to that of the perfect CSI case.Since our scheme will greatly compress the length of pilot sequence especially for those highly densified network with large number of small cells,it will be crucially helpful to put such two-tier massive multiple-input and multiple-output(MIMO) systems into practice.展开更多
Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the w...Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the weak signals. The analysis results show that the signal-to-noise ratio after beamforming was obviously enhanced, and the signal could be clearly shown. The energy from this explosion was mainly concentrated in the 1 -8Hz range from f-k analysis. The velocity spectrum gave clear positions of event phases, which could not be seen in the original weak signals. The maximum energy distribution obtained by the Beaman method is close to the theoretical value in the azimuth-slowness domain.展开更多
本文较为系统地阐述了发展空间太阳能发电卫星(space solar power satellite, SSPS)的几个问题.首先,论述了发展SSPS对世界人类从根本上解决能源危机,尤其是对我国生存与发展的极端重要性.其次,对聚光与非聚光两大类空间太阳能发电卫星...本文较为系统地阐述了发展空间太阳能发电卫星(space solar power satellite, SSPS)的几个问题.首先,论述了发展SSPS对世界人类从根本上解决能源危机,尤其是对我国生存与发展的极端重要性.其次,对聚光与非聚光两大类空间太阳能发电卫星的几个典型设计方案,从功质比(即单位质量所产生的电能)指标、工程实现、可靠性等方面,分析了它们的优缺点.再者,对作者团队2014年提出的SSPS-OMEGA方案的近期研究进展作了较为详细的讨论.最后,就本领域近期进展与未来需注意的几个理论与技术问题,提出了相应的观点.展开更多
基金supported in part by the "863" Program of China No. 2014AA01A704National Natural Science Foundation of China No.61171080
文摘Heterogeneous networks(HetNets)consisting of macro cells with very large antenna arrays and a secondary tier of small cells with a few antennas each can well tackle the contradiction of large coverage of the network and high data rate at the hot spots.However,it is not permissible to assign orthogonal pilot sequences for all the supported users due to the large number.Hence,we propose a pilot reduction scheme based on the heterogeneous system configurations and the unique topology of this HetNet.The reusing of pilot sequences causes the presence of the contaminated channel state information(CSI) and results in receivers' Quality of Service(QoS) outage.With the contaminated CSI,we provide an energy-efficient beamforming based on minimizing the total power consumption while keeping the QoS constraints satisfied and restricting the QoS outage probability below a given specification.By applying the approach of Bernstein approximation and semi-definite relaxation,we transform the original intractable chance constrained program to a convex problem conservatively.Numerical results show that the average power consumption of the proposed beamforming for our pilot reduction scheme is close to that of the perfect CSI case.Since our scheme will greatly compress the length of pilot sequence especially for those highly densified network with large number of small cells,it will be crucially helpful to put such two-tier massive multiple-input and multiple-output(MIMO) systems into practice.
基金The Basic Science Research Project of Commonweal of Nation Level (DQJB06A02 ),ChinaThe Brightlight (Ⅰ) Project from Institute of Geophysics,CEA
文摘Waveforms generated by the 50t explosion of project Brightlight （ I ） were recorded by HILR array. Using array techniques, the author performed identification, f-k analysis, velocity spectrum analysis, etc. of the weak signals. The analysis results show that the signal-to-noise ratio after beamforming was obviously enhanced, and the signal could be clearly shown. The energy from this explosion was mainly concentrated in the 1 -8Hz range from f-k analysis. The velocity spectrum gave clear positions of event phases, which could not be seen in the original weak signals. The maximum energy distribution obtained by the Beaman method is close to the theoretical value in the azimuth-slowness domain.
文摘本文较为系统地阐述了发展空间太阳能发电卫星(space solar power satellite, SSPS)的几个问题.首先,论述了发展SSPS对世界人类从根本上解决能源危机,尤其是对我国生存与发展的极端重要性.其次,对聚光与非聚光两大类空间太阳能发电卫星的几个典型设计方案,从功质比(即单位质量所产生的电能)指标、工程实现、可靠性等方面,分析了它们的优缺点.再者,对作者团队2014年提出的SSPS-OMEGA方案的近期研究进展作了较为详细的讨论.最后,就本领域近期进展与未来需注意的几个理论与技术问题,提出了相应的观点.
