Integrating the reconfigurable intelligent surface in a cell-free (RIS-CF) network is an effective solution to improve the capacity and coverage of future wireless systems with low cost and power consumption. The reflecting coefficients of RISs can be programmed to enhance signals received at users. This letter addresses a joint design of transmit beamformers at access points and reflecting coefficients at RISs to maximize the energy efficiency (EE) of RIS-CF networks, taking into account the limited backhaul capacity constraints. Due to a very computationally challenging nonconvex problem, we develop a simple yet efficient alternating algorithm for its solution. Numerical results verify that the EE of RIS-CF networks is greatly improved, showing the benefit of using RISs.

中文翻译：

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具有有限回程的 RIS 辅助无蜂窝网络的能效最大化

在无蜂窝（RIS-CF）网络中集成可重构智能表面是一种有效的解决方案，可以以低成本和功耗提高未来无线系统的容量和覆盖范围。可以对 RIS 的反射系数进行编程，以增强用户接收到的信号。这封信讨论了在接入点的发射波束成形器和 RIS 的反射系数的联合设计，以最大限度地提高 RIS-CF 网络的能源效率 (EE)，同时考虑到有限的回程容量限制。由于一个非常具有计算挑战性的非凸问题，我们为其解决方案开发了一种简单而有效的交替算法。数值结果验证了 RIS-CF 网络的 EE 大大提高，显示了使用 RIS 的好处。