To simplify the model derivation, the MBS transmission power is normalized as P0 = 40 W with coverage radius r0 = 1 km [7]. Similarly, the BS transmission power with coverage radius r is denoted by PTX = P0 ◊ (r/r0)a, where a is the path loss coefficient. Furthermore, the BS operating power with coverage radius r is expressed as POP = a ◊ P0 ◊ (r/r0)a + b. The BS embodied energy includes the initial energy and the maintenance energy, which is calculated by EEM = EEMinit + EEMmaint. In the central solution, the system energy consumption is expressed by