Uplink Power Optimization Strategies for Cell-Free Wireless Systems with Multiple Aerial Relay Stations

Abstract

Cell-Free (CF) wireless systems have increasingly demonstrated their outstanding advantages and are considered a promising technology for future 6G networks. This paper investigates the uplink performance of a CF system supported by unmanned aerial vehicle (UAV) acting as aerial relay station (ARS). Each ARS is equipped with multiple antennas and is randomly deployed within a specific area to simultaneously serve multiple ground users. During the uplink training phase, ARS estimate the channels and subsequently separate the received signals based on the estimated channels. To enhance the overall system performance, a power allocation optimization method for data transmission is proposed. Additionally, a closed-form expression for the achievable uplink rate is derived using the matched filtering technique, and a bisection approach is employed to solve the optimization problem. The study evaluates the user throughput under varying system parameters such as the number of users, ARS, and pilot sequence length. Simulation results demonstrate that the optimized user throughput is significantly higher than that of the non-optimized case.