Testbed Development: An Intelligent O-RAN-Based Cell-Free MIMO Network

Cell-free multiple input multiple output (CF-MIMO) systems improve spectral and energy efficiencies using distributed access points (APs) to provide reliable service across an area equivalent to multiple conventional cells. This article presents a novel design and implementation of a CF-MIMO network leveraging the open radio access network (O-RAN) architecture-based testbed to enhance the performance of interference-prone users. The proposed prototype is developed based on open-source software components, and unlike many other prototypes, our testbed is able to serve commercial 5G user equipment (UE). The RAN intelligent controller (RIC) allows the cell-free (CF) network to access the embedded artificial intelligence and benefit from the network optimization techniques that O-RAN brings. The testbed includes an intelligent antenna association xApp, which determines the antenna group that serves each UE based on the live key performance measurements. The article demonstrates the deployment and operation of the CF network and the xApp and discusses how the CF networks can benefit from the O-RAN architecture.