标题： STAR-RIS辅助的SWIPT系统：主动还是被动？ 显示英文标题

标题： STAR-RIS Assisted SWIPT Systems: Active or Passive?

摘要： 一种同时发射和反射的可重构智能表面（STAR-RIS）辅助的同时无线信息和功率传输（SWIPT）系统被研究。 考虑了主动和被动的STAR-RIS。 被动STAR-RIS可以以低成本高效地制造出具有显著近场区域的大孔径尺寸，但其设计灵活性受到耦合相移的限制。 主动STAR-RIS可以进一步放大信号并具有独立的相移，但由于成本较高，其孔径尺寸相对较小。 为了表征和比较它们的性能，通过联合设计接入点（AP）和STAR-RIS的波束成形，在满足功率和信息服务质量要求的情况下，制定了一个功率消耗最小化问题。 为了解决高度耦合的非凸问题，首先将原问题分解为更简单的子问题，然后提出了一种交替优化框架。 对于被动STAR-RIS，通过采用矢量驱动的权重惩罚方法来处理耦合相移约束。 而对于主动STAR-RIS，则通过矩阵驱动的半定规划优化AP波束成形中的独立相移，并在每次迭代中使用凸优化技术更新幅度矩阵。 数值结果表明：1）在相同孔径尺寸下，当孔径尺寸较小时，主动STAR-RIS表现出优于被动STAR-RIS的性能，但随着孔径尺寸的增加，性能差距减小；2）在相同的功率预算下，被动STAR-RIS通常更受青睐，而主动STAR-RIS在平衡硬件功率和放大功率之间通常会遭受性能损失。 显示英文摘要

摘要： A simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted simultaneous wireless information and power transfer (SWIPT) system is investigated. Both active and passive STAR-RISs are considered. Passive STAR-RISs can be cost-efficiently fabricated to large aperture sizes with significant near-field regions, but the design flexibility is limited by the coupled phase-shifts. Active STAR-RISs can further amplify signals and have independent phase-shifts, but their aperture sizes are relatively small due to the high cost. To characterize and compare their performance, a power consumption minimization problem is formulated by jointly designing the beamforming at the access point (AP) and the STAR-RIS, subject to both the power and information quality-of-service requirements. To solve the resulting highly-coupled non-convex problem, the original problem is first decomposed into simpler subproblems and then an alternating optimization framework is proposed. For the passive STAR-RIS, the coupled phase-shift constraint is tackled by employing a vector-driven weight penalty method. While for the active STAR-RIS, the independent phase-shift is optimized with AP beamforming via matrix-driven semidefinite programming, and the amplitude matrix is updated using convex optimization techniques in each iteration. Numerical results show that: 1) given the same aperture sizes, the active STAR-RIS exhibits superior performance over the passive one when the aperture size is small, but the performance gap decreases with the increase in aperture size; and 2) given identical power budgets, the passive STAR-RIS is generally preferred, whereas the active STAR-RIS typically suffers performance loss for balancing between the hardware power and the amplification power.