  In this paper, we pursue a unified study on smart grid and coordinated
multi-point (CoMP) enabled wireless communication by investigating a new joint
communication and energy cooperation approach. We consider a practical CoMP
system with clustered multiple-antenna base stations (BSs) cooperatively
communicating with multiple single-antenna mobile terminals (MTs), where each
BS is equipped with local renewable energy generators to supply power and also
a smart meter to enable two-way energy flow with the grid. We propose a new
energy cooperation paradigm, where a group of BSs dynamically share their
renewable energy for more efficient operation via locally injecting/drawing
power to/from an aggregator with a zero effective sum-energy exchanged. Under
this new energy cooperation model, we consider the downlink transmission in one
CoMP cluster with cooperative zero-forcing (ZF) based precoding at the BSs. We
maximize the weighted sum-rate for all MTs by jointly optimizing the transmit
power allocations at cooperative BSs and their exchanged energy amounts subject
to a new type of power constraints featuring energy cooperation among BSs with
practical loss ratios. Our new setup with BSs' energy cooperation generalizes
the conventional CoMP transmit optimization under BSs' sum-power or
individual-power constraints. Finally, we validate our results by simulations
under various practical setups, and show that the proposed joint communication
and energy cooperation scheme substantially improves the downlink throughput of
CoMP systems powered by smart grid and renewable energy, as compared to other
suboptimal designs without communication and/or energy cooperation.
