  This paper proposes the utilization of cell-free massive MIMO (CF-M-MIMO)
processing on top of the regular micro/macrocellular deployments typically
found in current 5G networks. Towards this end, it contemplates the connection
of all base stations to a central processing unit (CPU) through fronthaul
links, thus enabling the joint processing of all serviced user equipment (UE),
yet avoiding the expensive deployment and maintenance of dozens of randomly
scattered access points (APs). Moreover, it allows the implementation of
centralized strategies to exploit the sleep mode capabilities of current
baseband/RF hardware to (de)activate selected Base Stations (BSs) in order to
maximize the network energy efficiency and to react to changes in UE behaviour
and/or operator requirements. In line with current cellular network
deployments, it considers the use of multiple antennas at the UE side that
unavoidably introduces the need to effectively manage the number of streams to
be directed to each UE in order to balance multiplexing gains and increased
pilot contamination.
