Pradhan Anish, Alamzadeh Idban, Imani Mohammadreza F, Dhillon Harpreet S
Wireless@VT, Bradley Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, 24061, VA, USA.
School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, 85287, AZ, USA.
Sci Rep. 2024 Dec 28;14(1):30659. doi: 10.1038/s41598-024-73693-1.
Owing to the ability of reconfigurable intelligent surfaces (RISs) to control the propagation environment in their vicinity, they have emerged as an appealing solution to enhance the performance of next-generation wireless networks. While the effectiveness of RISs with complete channel state information (CSI) is well-documented, their performance with limited user information remains less explored. This is particularly pronounced when an RIS interferes with nodes in a potentially non-cooperating network, making CSI acquisition challenging. This paper focuses on such scenarios, examining the interference suppression capabilities of an RIS for coexisting secondary and primary users (SUs and PUs) using angular information, achievable even with non-cooperating PUs. We address the coexistence challenge by employing semidefinite relaxation (SDR) and inner majorization minimization (iMM) for RISs with continuous phase control, and propose an enhanced SDR tailored for discrete RISs. Numerical results reveal both SDR and iMM require at least five bits of discrete phase control for moderate interference suppression. They also indicate that interference suppression weakens if the PUs are inside certain angular regions, a limitation that varies with the algorithm but can be mitigated by increasing RIS elements. Ultimately, the coexistence performance of the RIS with a non-cooperative network is validated through full-wave simulations.
由于可重构智能表面（RIS）能够控制其附近的传播环境，它们已成为一种有吸引力的解决方案，以提高下一代无线网络的性能。虽然具有完整信道状态信息（CSI）的RIS的有效性已有充分记录，但它们在用户信息有限时的性能仍较少被探索。当RIS干扰潜在非合作网络中的节点时，这一点尤为明显，使得CSI获取具有挑战性。本文关注此类场景，研究了即使在非合作主用户（PU）的情况下，利用角度信息的RIS对共存的次用户和主用户（SU和PU）的干扰抑制能力。我们通过对具有连续相位控制的RIS采用半定松弛（SDR）和内主元最小化（iMM）来解决共存挑战，并针对离散RIS提出了一种增强型SDR。数值结果表明，SDR和iMM都需要至少五位的离散相位控制才能实现适度的干扰抑制。结果还表明，如果PU位于某些角度区域内，干扰抑制会减弱，这种限制因算法而异，但可以通过增加RIS元素来缓解。最终，通过全波模拟验证了RIS与非合作网络的共存性能。
