Joint Uplink and Downlink Resource Allocation for Cell-Free Radio Access Network with Network-Assisted Free Duplex

This paper proposes a network-assisted free duplex (NA-FD) architecture for the cell-free radio access network (CF-RAN) system. In this architecture, users operate in half-duplex mode, while access points (APs) support both full-duplex and half-duplex modes. Uplink signals from users are transmitted to APs, which forward them to edge distributed units (EDUs). The EDUs demodulate the signals and send the data to the central processing unit (CPU) for integration. Simultaneously, the CPU sends downlink data to the EDUs, which perform precoding and transmit the signals to the respective downlink users through associated APs. As a result, CF-RAN meets the requirements of low latency and ultra-reliable communication. Our research aims to maximize the system spectral efficiency by resource scheduling. To achieve this, we fist adopt a graph coloring algorithm to solve the EDU-AP association problem, and then use coalition game theory to determine the duplex mode of APs. Through extensive simulations, we demonstrate the efficacy of the proposed architecture in optimizing resource allocation, thereby significantly improving system performance and enhancing user quality of service.