For the influence caused by multipath fading and non-line-of-sight(NLOS)transmission,it is challenging to accurately localize a moving signal source in complex environment by using the wireless sensor network(WSN)on t...For the influence caused by multipath fading and non-line-of-sight(NLOS)transmission,it is challenging to accurately localize a moving signal source in complex environment by using the wireless sensor network(WSN)on the ground.In this paper,we establish a special WSN in the sky to address this challenge,where each sensor is loaded on an unmanned aerial vehicle(UAV)and the operation center of all the UAVs is fixed on the ground.Based on the analyzing of the optimal distribution and the position error calibration of all the sensors,we formulate the localization scheme to estimate the position of the target source,which combines the time difference of arrival(TDOA)method and the frequency difference of arrival(FDOA)method.Then by employing the semidefinite programming approach,we accurately obtain the position and velocity of the signal source.In the simulation,the validity of the proposed method is verified through the performance comparison.展开更多
We first study the reversibility for a class of states under the operations which completely preserve the positivity of partial transpose（PPT） and show that the entanglement cost is equal to the distillable entangle...We first study the reversibility for a class of states under the operations which completely preserve the positivity of partial transpose（PPT） and show that the entanglement cost is equal to the distillable entanglement for a rank-two mixed state on the 4 4 antisymmetric subspace under PPT operations. By using a similar method in finding the irreversibility,we also find that the value of a new efficiently computable additive lower bound Eη（ρ） for the asymptotic PPT-relative entropy of entanglement presented in [Phys. Rev. Lett. 119, 180506（2017）] is equal to the regularized Rains＇ bound and an upper bound EN（ρ） for distillable entanglement for these states. Furthermore, we find states on the symmetric subspace satisfying the relation mentioned above, generalize the antisymmetric states and symmetric states in higher dimensions, and give a specific value for distillable entanglement and entanglement cost for these states under the PPT operations.展开更多
Most of studies on Distributed Antenna System(DAS) focus on maximizing the sum capacity and perfect channel state information at transmitter(CSIT).However,CSI is inevitable imperfect in practical wireless networks.Bas...Most of studies on Distributed Antenna System(DAS) focus on maximizing the sum capacity and perfect channel state information at transmitter(CSIT).However,CSI is inevitable imperfect in practical wireless networks.Based on the sources of error,there are two models.One assumes error lies in a bounded region,the other assumes random error.Accordingly,we propose two joint antenna selection(AS) and robustbeamforming schemes aiming to minimize the total transmit power at antenna nodes subject to quality of service(QoS) guarantee for all the mobile users(MUs) in multicell DAS.This problem is mathematically intractable.For the bounded error model,we cast it into a semidefinite program(SDP) using semidefinite relaxation(SDR) and S-procedure.For the second,we first design outage constrained robust beamforming and then formulate it as an SDP based on the Bernstein-type inequality,which we generalize it to the multi-cell DAS.Simulation results verify the effectiveness of the proposed methods.展开更多
基金supported by The Science and Technology Innovation Team Plan of Shaanxi Province (2017-KCT-30-02)The Key Research and Development Program of Shaanxi Province (2018GY-150)+1 种基金The Foundation Research Project of Shaanxi Province (The Natural Science Fund. 2018JQ6093)The Science and Technology Plan Project of Xi’an City (201805040YD18CG24-3)
文摘For the influence caused by multipath fading and non-line-of-sight(NLOS)transmission,it is challenging to accurately localize a moving signal source in complex environment by using the wireless sensor network(WSN)on the ground.In this paper,we establish a special WSN in the sky to address this challenge,where each sensor is loaded on an unmanned aerial vehicle(UAV)and the operation center of all the UAVs is fixed on the ground.Based on the analyzing of the optimal distribution and the position error calibration of all the sensors,we formulate the localization scheme to estimate the position of the target source,which combines the time difference of arrival(TDOA)method and the frequency difference of arrival(FDOA)method.Then by employing the semidefinite programming approach,we accurately obtain the position and velocity of the signal source.In the simulation,the validity of the proposed method is verified through the performance comparison.
基金Project supported by the National Natural Science Foundation of China(Grant No.11671244)
文摘We first study the reversibility for a class of states under the operations which completely preserve the positivity of partial transpose（PPT） and show that the entanglement cost is equal to the distillable entanglement for a rank-two mixed state on the 4 4 antisymmetric subspace under PPT operations. By using a similar method in finding the irreversibility,we also find that the value of a new efficiently computable additive lower bound Eη（ρ） for the asymptotic PPT-relative entropy of entanglement presented in [Phys. Rev. Lett. 119, 180506（2017）] is equal to the regularized Rains＇ bound and an upper bound EN（ρ） for distillable entanglement for these states. Furthermore, we find states on the symmetric subspace satisfying the relation mentioned above, generalize the antisymmetric states and symmetric states in higher dimensions, and give a specific value for distillable entanglement and entanglement cost for these states under the PPT operations.
基金ACKNOWLEDGEMENTS This work is supported by Natural Science Foundation of China （No. 61340035） and Guangzhou science and technology plan projects （2014-132000764）.
文摘Most of studies on Distributed Antenna System(DAS) focus on maximizing the sum capacity and perfect channel state information at transmitter(CSIT).However,CSI is inevitable imperfect in practical wireless networks.Based on the sources of error,there are two models.One assumes error lies in a bounded region,the other assumes random error.Accordingly,we propose two joint antenna selection(AS) and robustbeamforming schemes aiming to minimize the total transmit power at antenna nodes subject to quality of service(QoS) guarantee for all the mobile users(MUs) in multicell DAS.This problem is mathematically intractable.For the bounded error model,we cast it into a semidefinite program(SDP) using semidefinite relaxation(SDR) and S-procedure.For the second,we first design outage constrained robust beamforming and then formulate it as an SDP based on the Bernstein-type inequality,which we generalize it to the multi-cell DAS.Simulation results verify the effectiveness of the proposed methods.
