摘要：
Energy management and power allocation policy is considered for energy harvesting (EH) communications. In this letter, we propose a joint optimization problem with the continuous EH time and transmit power to maximize the long-term throughput based on deep deterministic policy gradient (DDPG). However, the joint optimization problem leads to a large continuous action space. In order to reduce the dimension of action space, we present a deep reinforcement learning (DRL) framework by combining DDPG and convex program. The original problem is decomposed into two-layer optimization subproblems by using the primal decomposition method. The primary problem can be solved by DDPG with a low-dimensional action space. The lower-layer subproblem can be solved by using the existing convex toolbox. Numerical simulation results show that, compared with the existing energy management or power allocation policies for EH communications, the proposed DRL framework can achieve higher long-term throughput.
作者机构：
[Zhou, Aizhi; Xu, Hongbo; Fan, Lvrong; Zhu, Bingru; Wang, Jun] Cent China Normal Univ, Dept Elect & Informat Engn, Wuhan 430079, Hubei, Peoples R China.;[Wang, Jun] Shenzhen Univ, Coll Informat Engn, Shenzhen 518060, Peoples R China.
通讯机构：
[Xu, Hongbo] C;Cent China Normal Univ, Dept Elect & Informat Engn, Wuhan 430079, Hubei, Peoples R China.
关键词：
Radio frequency;Array signal processing;Unicast;Interference;Optimization;Precoding;Antenna arrays
摘要：
In this letter, we investigate the beamforming design for millimeter-wave (mmWave) joint unicast and multicast (JUM) systems, in which the common and private signals are transmitted simultaneously. Due to the hardware limitation, the conventional fully digital beamforming methods are infeasible. We propose a suboptimal low-complexity hybrid zero-forcing (ZF) beamforming scheme for the mmWave JUM systems. The analog precoder and combiner are first optimized to maximize the effective channel gains. The ZF algorithm is then used to decide the unicast beamforming directions for cancelling the inter-user interference so that the optimization problem is reduced. With the unicast beamforming directions, the unicast power allocation and multicast beamformer are finally optimized by employing successive convex approximation (SCA) iteratively. The simulation results demonstrate that the sum-rate of the proposed algorithm is slightly inferior to the fully digital beamforming algorithm, but outperforms the orthogonal multiple access scheme.
摘要：
In this letter, we investigate the secure beamforming design for multiuser multiple-input single-output interference channel with an eavesdropper. The robust secrecy rate optimization problem is studied with the imperfect channel state information. We consider the beamforming design to maximize the minimum worst case secrecy rate subject to the transmit power constraints with norm-bounded channel uncertainty. The problem is non-convex and hard to solve. We propose an effective method to reformulate this non-convex problem as a series of tractable convex program problems with linear matrix inequality and second-order cone constraints by exploiting the conservative approximation and the sequential convex approximation methods. The simulation results demonstrate the effectiveness of the proposed algorithm.
期刊：
IET Communications,2016年10(15):1964-1970 ISSN：1751-8628
通讯作者：
Xu, Hongbo
作者机构：
[Zhou, Aizhi; Xu, Hongbo; Liu, Jun] Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan, Peoples R China.
通讯机构：
[Xu, Hongbo] C;Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan, Peoples R China.
关键词：
array signal processing;optimisation;interference;iterative methods;wireless channels;distributed energy efficiency beamforming design;multiple-input-single-output interference channels;coordinated beamforming designs;transformed optimisation problem;iterative process
摘要：
Coordinated beamforming designs based on energy efficiency of multiple-user interference channels have attracted much attention. The optimisation problem has a fractional form, and is coupled among users, which makes it difficult to be solved directly. A beamforming design for energy-efficient communication in multiple-input-single-output interference channels is studied, and proposes an efficient distributed approach to solve it. A novel method is developed to transform the optimisation problem into a DC (difference of two convex/concave functions) structure. The transformed optimisation problem is approximated by using a separable structure across the users, and this approximated version is solved iteratively. Numerical results show the effectiveness of the authors' proposed algorithm.
作者：
Zhang, Ping;Li, Jun;Zhou, Ai Zhi（周爱芝）;Xu, Hong Bo;Bi, Jian
期刊：
Progress In Electromagnetics Research C,2013年43:53-65 ISSN：1937-8718
通讯作者：
Li, J.(jl.9530@gmail.com)
作者机构：
[Zhou, Ai Zhi; Bi, Jian; Zhang, Ping; Xu, Hong Bo] College of Physical Science and Technology, Central China Normal University, Wuhan 430079, China;[Li, Jun] Department of Electronics and Information Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
通讯机构：
Department of Electronics and Information Engineering, Huazhong University of Science and Technology, China
摘要：
A robust direct data domain least squares (D3LS) beamforming algorithm that is capable of reducing the sidelobe level of the beam pattern is presented. By exploiting the sparsity of the desired beam pattern, the proposed method can enhance the performance with its lower sidelobe level and deeper null for interference while the robustness against steering vector mismatch is increased when a proper regularization parameter is selected. Simulation results demonstrate the effectiveness of the proposed method.
摘要：
The first order deconfinement phase transitions in rotating hybrid stars are studied and it is found that if the surface tension is sufficiently large, the transition from metastable hadron matter to stable mixed hadron-quark matter during the spin-down history of a hybrid star can cause a glitch.
摘要：
We have investigated the thermal evolution of rotating strange stars with the deconfinement heating due to magnetic braking. We consider stars consisting of either normal quark matter or a color-flavor-locked phase. Combining deconfinement heating with magnetic-field decay, we find that the thermal evolution curves are identical to those from pulsar data, solving the problem of scarce data for old strange stars.
