In this paper, we propose a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) empowered transmission scheme for symbiotic radio (SR) systems to make more flexibility for network deployment and enhance system performance. The STAR-RIS is utilized to not only beam the primary signals from the base station (BS) towards multiple primary users on the same side of the STAR-RIS, but also achieve the secondary transmission to the secondary users on another side. We consider both the broadcasting signal model and unicasting signal model at the BS. For each model, we aim for minimizing the transmit power of the BS by designing the active beamforming and simultaneous reflection and transmission coefficients under the practical phase correlation constraint. To address the challenge of solving the formulated problem, we propose a block coordinate descent based algorithm with the semidefinite relaxation, penalty dual decomposition and successive convex approximation methods, which decomposes the original problem into one sub-problem about active beamforming and the other sub-problem about simultaneous reflection and transmission coefficients, and iteratively solve them until the convergence is achieved. Numerical results indicate that the proposed scheme can reduce up to 150.6% transmit power compared to the backscattering device enabled scheme.
翻译:在本文中,我们提出了一种同时传输和反射的可重构智能表面 (STAR-RIS) 强化的传输方案,用于共生无线电 (SR) 系统,以使网络部署更加灵活并增强系统性能。 STAR-RIS 用于将基站 (BS) 的主要信号向同一侧的多个主要用户进行波束传输,同时在另一侧实现二次传输到次要用户。我们考虑 BS 中的广播信号模型和单播信号模型。对于每个模型,我们旨在设计活动波束成形和同时反射和传输系数,以在实际相位相关约束下最小化 BS 的传输功率。为解决解决所构建问题的挑战,我们提出了一种基于块坐标下降算法的半定松弛、罚双分解和逐次凸逼近方法,它将原问题分解为一个关于活性波束成形的子问题和关于同时反射和传输系数的另一个子问题,并迭代地解决它们,直到达到收敛。结果表明,与背散射装置启用方案相比,所提出的方案可以降低高达 150.6% 的传输功率。