Cell-Free Massive MIMO Deployments: Fronthaul Topology Options and Techno-Economic Aspects

Cell-free (CF) massive multiple-input multiple-output (MIMO) networks are an alternative to achieve a higher a more uniform signal-to-interference-plus-noise ratio (SINR) over a mobile coverage area. Most of the literature for these networks considers a star fronthaul topology. This topology may lead to a non-scalable complex and costly fronthaul network. Some works proposed serial interconnection among several access points (APs) to a Central Processing Unit (CPU) to solve this problem, an alternative we call cell-free with segmented fronthaul. However, there is a lack of studies investigating if this alternative is cost-saving. This work explores the technical-economic feasibility of cell-free with segmented fronthaul based on bus, star, ring, and tree topologies. Moreover, evaluations are made in terms of multiple levels of serialization, which are the number of APs connected serially. Results show that the best overall topology is tree-based with a low serialization level.