  We consider an energy minimization problem for cooperative LTE networks. To
reduce energy consumption, we investigate how to jointly optimize the transmit
power and the association between cells and user equipments (UEs), by taking
into consideration joint transmission (JT), one of the coordinated multipoint
(CoMP) techniques. We formulate the optimization problem mathematically. For
solving the problem, a dynamic power allocation algorithm that adjusts the
transmit power of all cells, and an algorithm for optimizing the cell-UE
association, are proposed. The two algorithms are iteratively used in an
algorithmic framework to enhance the energy performance. Numerically, the
proposed algorithms can lead to lower energy consumption than the optimal
energy setting in the non-JT case. In comparison to fixed power allocation in
JT, the proposed dynamic power allocation algorithm is able to significantly
reduce the energy consumption.
