Beamforming Design for Active-RIS-Aided Cell-Free Massive MIMO Networks Under Imperfect CSI.

Area of Science:

• Wireless communication networks
• Signal processing
• Information theory

Background:

• The development of 6G networks demands enhanced capacity and reduced power consumption.
• Reconfigurable intelligent surfaces (RISs) and cell-free (CF) massive MIMO are key enabling technologies for future wireless systems.
• Optimizing these systems under imperfect channel state information (CSI) presents a significant challenge.

Purpose of the Study:

• To investigate an active-RIS-aided CF massive MIMO system with imperfect CSI.
• To address the non-convex max-min achievable rate problem.
• To propose an efficient two-step optimization algorithm for system performance enhancement.

Main Methods:

• Decomposition of the non-convex problem into two subproblems.
• Alternating optimization of access point (AP) transmit beamforming and RIS reflecting precoding.
• Analysis under imperfect channel state information (CSI).

Main Results:

• The proposed two-step optimization algorithm effectively solves the max-min achievable rate problem.
• Simulation results show significant performance gains compared to existing methods.
• The scheme demonstrates superiority in active-RIS-aided CF massive MIMO systems.

Conclusions:

• The developed optimization strategy is effective for active-RIS-aided CF massive MIMO systems.
• The approach offers a viable solution for enhancing network capacity and efficiency.
• Future research can build upon this framework for advanced wireless network design.