Energy Cost Minimization in Heterogeneous Cellular Networks with Hybrid Energy Supplies

Figure 3

An illustration of the feasibility of energy cost minimization. The line between a BS and a user indicates the user associated with the BS, and the number on the line is its energy consumption. The green, blue, and brown rectangles represent the residual green energy from previous slots, green energy generated at the current slot, and the assigned green energy at the current slot, respectively.

(a) With no optimization

(b) With optimization in spatial traffic distribution

(c) With optimization in both spatial traffic distribution and temporal green energy allocation