Algorithm 3: Joint Device Association and Power Control Online Optimization (JDAPCOO) algorithm

1:Input: Device set $\mathcal{I}$, UAV set $\mathcal{U}$, ground 5G base station set $\mathcal{B}$, channel state information, PD power maximum $P_{max}$ and the minimum transmission rate requirement of the PDs $R_{th}$. 2:Output: Optimal device association strategy $\{{\mathbf{x}}_{\mathrm{u}},{\mathbf{x}}_{\mathrm{b}}\}$ and optimal power control scheme $\left\{\mathbf{P}\right\}$. 3:repeat 4:for each time slot do 5:   Initialize PDs’ power and decide the device association strategy ${\mathbf{x}}_{\mathrm{u}}\left(t\right)$ and ${\mathbf{x}}_{\mathrm{b}}\left(t\right)$ according to Algorithm 1. 6:   Based on ${\mathbf{x}}_{\mathrm{u}}\left(t\right)$ and ${\mathbf{x}}_{\mathrm{b}}\left(t\right)$ obtained from Algorithm 1, the power control scheme $\mathbf{P}\left(t\right)$ is decided using Algorithm 2. 7:   Update channel state information. 8:   $t=t+1$. 9:end for 10:until $t>T$. 11:Return $\{{\mathbf{x}}_{\mathrm{u}},{\mathbf{x}}_{\mathrm{b}}$ and $\mathbf{P}\}$.