Scalable Network-Assisted Full-Duplex Cell-Free Massive MIMO With Limited Fronthaul Capacity

This paper proposes a scalable network-assisted full-duplex (NAFD) cell-free massive multiple-input multiple-output (CF-mMIMO) system that achieves high spectral efficiency (SE) while reducing the fronthaul load by forming clusters of access points (APs) exclusively for uplink and downlink based on user equipment (UE) requirements, respectively. Specifically, we propose AP clustering techniques based on convex optimization and Hungarian algorithm, along with downlink transmit power control suitable for proposed AP clustering. Numerical results demonstrate that our proposed approach achieves higher SE than conventional scalable TDD CF-mMIMO, NAFD CF-mMIMO and small cell with dynamic time division duplex (TDD), under fronthaul capacity limitations.