Abstract
Cell-free (CF) network is a favorable technique against inter-cell interferences to improve the network capacity. However, to further improve the network capacity, a large number of base stations (BSs) are required to be deployed with high cost and power consumption. To tackle this problem, an energy-efficient technique called reconfigurable intelligent surface (RIS)-aided CF network has been recently proposed. By replacing some of the required power-hungry BSs with low-power RISs, the energy efficiency of CF network can be enhanced with guaranteed performance. To achieve this goal, in this paper, we first formulate a joint active and passive beamforming problem to maximize the energy efficiency of RIS-aided CF networks. Then, we propose an alternate optimization algorithm to solve this problem. Specifically, we decompose the original energy efficiency maximization problem into multiple subproblems and solve them alternatively. Particularly, we adopt the zero-forcing (ZF) beamforming scheme to optimize the active beamforming at BSs, while the sequential programming (SP) method is adopted to realize the passive beamforming at RISs. Moreover, a realistic energy-consumption model for wideband RIS-aided CF networks is provided, and the effectiveness of the proposed scheme is evaluated by simulations. Finally, simulation results verify that, the proposed scheme is able to achieve a higher energy efficiency than the existing benchmark solution.
Highlights
W IRELESS communication systems are expected to support high data rate applications, such as augmented reality and virtual reality [1]
SIMULATION RESULTS we verify the effectiveness of the proposed SF-based scheme under different simulation settings for the wideband reconfigurable intelligent surface (RIS)-aided CF wireless network
The CF network configuration is composed of four base stations (BSs), two RISs, and four single-antenna users
Summary
W IRELESS communication systems are expected to support high data rate applications, such as augmented reality and virtual reality [1] To achieve this goal, various promising techniques such as massive multipleinput and multiple-output (MIMO) [2], millimeter-wave (mmWave) communication [3], and ultra-dense network (UDN) [4], [5] have been proposed. The densification of BSs will result in the severe inter-cell interferences, which fundamentally limit the network capacity [7]. To cope with this problem, the concept of cell-free (CF) network has recently been proposed in [8]. Energy consumption has become a challenging problem in future wireless networks to ensure green and sustainable wireless communications
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