  This paper studies the energy management in the coordinated multi-point
(CoMP) systems powered by smart grids, where each base station (BS) with local
renewable energy generation is allowed to implement the two-way energy trading
with the grid. Due to the uneven renewable energy supply and communication
energy demand over distributed BSs as well as the difference in the prices for
their buying/selling energy from/to the gird, it is beneficial for the
cooperative BSs to jointly manage their energy trading with the grid and energy
consumption in CoMP based communication for reducing the total energy cost.
Specifically, we consider the downlink transmission in one CoMP cluster by
jointly optimizing the BSs' purchased/sold energy units from/to the grid and
their cooperative transmit precoding, so as to minimize the total energy cost
subject to the given quality of service (QoS) constraints for the users. First,
we obtain the optimal solution to this problem by developing an algorithm based
on techniques from convex optimization and the uplink-downlink duality. Next,
we propose a sub-optimal solution of lower complexity than the optimal
solution, where zero-forcing (ZF) based precoding is implemented at the BSs.
Finally, through extensive simulations, we show the performance gain achieved
by our proposed joint energy trading and communication cooperation schemes in
terms of energy cost reduction, as compared to conventional schemes that
separately design communication cooperation and energy trading.
