  Cellular networks are among the major energy hoggers of communication
networks, and their contributions to the global energy consumption increase
rapidly due to the surges of data traffic. With the development of green energy
technologies, base stations (BSs) can be powered by green energy in order to
reduce the on-grid energy consumption, and subsequently reduce the carbon
footprints. However, equipping a BS with a green energy system incurs
additional capital expenditure (CAPEX) that is determined by the size of the
green energy generator, the battery capacity, and other installation expenses.
In this paper, we introduce and investigate the green energy provisioning (GEP)
problem which aims to minimize the CAPEX of deploying green energy systems in
BSs while satisfying the QoS requirements of cellular networks. The GEP problem
is challenging because it involves the optimization over multiple time slots
and across multiple BSs. We decompose the GEP problem into the weighted energy
minimization problem and the green energy system sizing problem, and propose a
green energy provisioning solution consisting of the provision cost aware
traffic load balancing algorithm and the binary energy system sizing algorithm
to solve the sub-problems and subsequently solve the GEP problem. We validate
the performance and the viability of the proposed green energy provisioning
solution through extensive simulations, which also conform to our analytically
results.
