非线性能量收集下的鲁棒性波束赋形

在无线信息能量同步传输系统中，考虑实际电路实现中的非线性能量收集模型，提出了一种具有鲁棒性的波束赋形设计方案。为了提升系统用户间的公平性，对最小的用户信干噪比进行优化，并构建了一个非凸的优化问题。针对问题的非凸特性以及引入信道估计误差带来的限制条件，基于S过程对问题进行变形，并通过半定松弛技术对问题进行凸化，提出了一种基于二分法的迭代波束赋形算法。仿真结果表明，相比于非鲁棒性算法，所提的算法能够获得25%到50%的性能增益。因此，所提算法更加适用于实际系统中的非理想信道环境。仿真结果还表明所提算法相比于线性能量收集模型或迫零波束赋形等方法，能够取得更好的公平性能。 

Robust Beamforming under Non-Linear Energy Harvesting Model

A robust beamformer design was proposed in simultaneous wireless information and power transfer systems, where a practical non-linear energy harvester circuit model was taken into consideration. In order to improve the fairness among users in the system, the minimum signal-to-interference-plus-noise ratio was optimized, thus the overall receiving performance of users could be enhanced. A non-convex optimization was formulated under the consideration of imperfect channel state information, where the transmit beamformers of information receiver were optimized. To tackle the non-convexity and the infinite constraints brought by channel estimation errors, the problem was first reformulated based on S-procedure, and further convexified by using semidefinite relaxation. An iterative beamformer design was then proposed based on bisection method. Simulation results show that the proposed algorithm can achieve 25% to 50% performance gain, compared with the non-robust algorithm. Therefore, the proposed algorithm can be applied in practical systems with non-ideal channel environment. The results also show that the proposed algorithm can achieve better fairness performance, compared with traditional beamforming such as linear energy harvesting based method or zero forcing.