Sum-Throughput Maximization for Backscatter Devices in Pinching-Antenna-Enhanced Symbiotic Radio Systems

In this correspondence, we introduce the pinching antenna (PA) into symbiotic radio (SR) systems to mitigate thedouble-fadingeffect on SR signals by leveraging PA's capability of reconfiguring the wireless channel. Specifically, we consider a time division multiple access-based PA-enhanced SR system with multiple backscatter devices (BDs), and formulate an optimization problem to maximize the sum throughput of BDs by jointly optimizing the PA positions, reflection coefficients of BDs, and time-slot durations. To solve this non-convex optimization problem, we decompose it into two subproblems: one optimizes the reflection coefficients of BDs and time-slot durations, and the other optimizes the PA positions. The former is solved by deriving the closed-form solutions, while the latter is solved by devising an improved one-dimensional search algorithm. Based on the obtained solutions to the two subproblems, we propose an alternating optimization-based iterative algorithm. Numerical results demonstrate that the proposed algorithm achieves the near-optimal BDs' sum throughput compared to the exhaustive search algorithm, while exhibiting the lowest complexity among all benchmark algorithms.