Subset regularized zero-forcing precoders for cell-free C-RANs

Abstract

This paper formulates regularized zero-forcing (RZF) precoders that are both network- and user-centric for the downlink of centralized radio-access networks operating in a cell-free fashion. The transmission to every user involves a distinct subset of access points (APs), and every AP participates in the transmission to a distinct subset of users, hence the moniker subset precoders. These subsets, defined on the basis of the large-scale channel gains between users and APs, capture the most relevant signal and interference contributions while disregarding those whose processing is cost-ineffective and whose associated channel estimations would incur unnecessary overheads. With that, subset precoding approaches the performance of network-wide RZF, for the power allocation strategies of interest, while being scalable.