Massive Antenna Arrays with Low Front-End Hardware Complexity: An   Enabling Technology for the Emerging Small Cell and Distributed Network   Architectures
  This paper presents the current state-of-the-art of massive antenna array architectures with significant front-end hardware savings, as an enabler for future small and powerful cell nodes that will be able to carry massive MIMO technology. Radio frequency (RF) hardware architectures with a single power amplifier are reviewed, compared, and found superior to conventional MIMO implementations in terms of cost, dissipated heat, and physical size. This progress on the RF-side allows to merge the two competing cellular concepts of virtual and massive MIMO into a hybrid approach of remote radio heads with massive MIMO arrays. 
Vlasis I. Barousis, Mohammad A. Sedaghat, Ralf R. M\"uller and   Constantinos B. Papadias
cs.NI cs.IT math.IT