Full duplex (FD) radio has attracted extensive attention due to its co-time and co-frequency transceiving capability. {However, the potential gain brought by FD radios is closely related to the management of self-interference (SI), which imposes high or even stringent requirements on SI cancellation (SIC) techniques. When the FD deployment evolves into next-generation mobile networking, the SI problem becomes more complicated, significantly limiting its potential gains.} In this paper, we conceive a multi-cell FD networking scheme by deploying a reconfigurable intelligent surface (RIS) at the cell boundary to configure the radio environment proactively. To achieve the full potential of the system, we aim to maximize the sum rate (SR) of multiple cells by jointly optimizing the transmit precoding (TPC) matrices at FD base stations (BSs) and users and the phase shift matrix at RIS. Since the original problem is non-convex, we reformulate and decouple it into a pair of subproblems by utilizing the relationship between the SR and minimum mean square error (MMSE). The optimal solutions of TPC matrices are obtained in closed form, while both complex circle manifold (CCM) and successive convex approximation (SCA) based algorithms are developed to resolve the phase shift matrix suboptimally. Our simulation results show that introducing an RIS into an FD networking system not only improves the overall SR significantly but also enhances the cell edge performance prominently. More importantly, we validate that the RIS deployment with optimized phase shifts can reduce the requirement for SIC and the number of BS antennas, which further reduces the hardware cost and power consumption, especially with a sufficient number of reflecting elements. As a result, the utilization of an RIS enables the originally cumbersome FD networking system to become efficient and practical.

翻译：全双工（FD）无线通信因其同时同频收发能力而受到广泛关注。然而，FD无线通信带来的潜在增益与自干扰（SI）管理密切相关，这对自干扰消除（SIC）技术提出了高甚至苛刻的要求。当FD部署演进为下一代移动组网时，SI问题变得更加复杂，显著限制了其潜在增益。本文通过在小区的边界部署可重构智能表面（RIS）来主动配置无线环境，设计了一种多小区FD组网方案。为充分发挥系统潜力，我们通过联合优化FD基站（BS）和用户处的发射预编码（TPC）矩阵以及RIS处的相移矩阵，以最大化多个小区的和速率（SR）。由于原始问题是非凸的，我们利用SR与最小均方误差（MMSE）之间的关系，将其重新表述并分解为一对子问题。TPC矩阵的最优解以闭式形式获得，同时开发了基于复圆流形（CCM）和逐次凸近似（SCA）的算法来次优求解相移矩阵。仿真结果表明，将RIS引入FD组网系统不仅能显著提高整体SR，还能显著增强小区边缘性能。更重要的是，我们验证了具有优化相移的RIS部署可以降低对SIC的要求和基站天线数量，从而进一步降低硬件成本和功耗，尤其是在拥有足够数量反射单元的情况下。因此，RIS的应用使原本繁重的FD组网系统变得高效实用。