  Small cell networks (SCNs) have attracted great attention in recent years due
to their potential to meet the exponential growth of mobile data traffic and
the increasing demand for better quality of service and user experience in
mobile applications. Nevertheless, a wide deployment of SCNs has not happened
yet because of the complexity in the network planning and optimization, as well
as the high expenditure involved in deployment and operation. In particular, it
is difficult to provide grid power supply to all the small cell base stations
(SCBSs) in a cost effective way. Moreover, a dense deployment of SCBSs, which
is needed to meet the capacity and coverage of the next generation wireless
networks, will increase operators' electricity bills and lead to significant
carbon emission. Thus, it is crucial to exploit off-grid and green energy
sources to power SCNs, for which energy harvesting (EH) technology is a viable
solution. In this article, we will conduct a comprehensive study of EH-SCNs,
and investigate important aspects, including the feasibility analysis, network
deployment, and network operation issues. The advantages, as well as unique
challenges, of EH-SCNs will be highlighted, together with potential solutions
and effective design methodologies.
