  This paper studies a new concept so-called green cell-less radio frequency
(RF) wireless power transfer (WPT) networks. We consider a scenario in which
multiple indoor access points (APs) equipped with outdoor energy harvesters are
connected with a central control unit via backhaul links. Further, such APs
exploit the harnessed green energy to recharge wirelessly indoor devices under
the coordination of the control unit. Considering the network, we focus on AP
selection and beamforming optimization to maximize the total energy harvesting
(EH) rate. The resulting mathematical problem has the form of mixed-integer
optimization that is intractable to solve. Thus, we propose an algorithm to
tackle this difficulty. Through numerical results, we show the advantages of
the cell-less design over the conventional small-cell one to validate our
ideas. In particular, the issue on safety requirements of human exposure to RF
radiation is discussed. Finally, potential future research is provided.
