  The applications of wireless power transfer technology to wireless
communications can help build a wireless powered communication network (WPCN)
with more reliable and sustainable power supply compared to the conventional
battery-powered network. However, due to the fundamental differences in
wireless information and power transmissions, many important aspects of
conventional battery-powered wireless communication networks need to be
redesigned for efficient operations of WPCNs. In this paper, we study the
placement optimization of energy and information access points in WPCNs, where
the wireless devices (WDs) harvest the radio frequency energy transferred by
dedicated energy nodes (ENs) in the downlink, and use the harvested energy to
transmit data to information access points (APs) in the uplink. In particular,
we are interested in minimizing the network deployment cost with minimum number
of ENs and APs by optimizing their locations, while satisfying the energy
harvesting and communication performance requirements of the WDs. Specifically,
we first study the minimum-cost placement problem when the ENs and APs are
separately located, where an alternating optimization method is proposed to
jointly optimize the locations of ENs and APs. Then, we study the placement
optimization when each pair of EN and AP are co-located and integrated as a
hybrid access point, and propose an efficient algorithm to solve this problem.
Simulation results show that the proposed methods can effectively reduce the
network deployment cost and yet guarantee the given performance requirements,
which is a key consideration in the future applications of WPCNs.
