Algorithm 3 Prioritized-based multiple contact-duration frame selection mechanisms (PMCdFS) algorithm.

Input: Initial deployed information of nodes and UAVs, ${\mathbb{S}}_{kB}^{1,2}$, ${\mathbb{S}}_{kB}^1$, ${\mathbb{S}}_{kB}^2$.

Output:${\mathbb{S}}_{kB}^1$ and ${\mathbb{S}}_{kB}^2$

1: for $\forall S_i\in {\mathbb{S}}_{k_B}^{1,2}$ do

2:        Calculate the contact duration between $S_i$ and the $UA{V}_1$ (denoted as $T_{i,1}$), the $UA{V}_2$ (denoted as $T_{i,2}$), respectively;

3:        if $T_{i,1}<T_{i,2}$ then

4:                ${\mathbb{S}}_{kB}^2$ = ${\mathbb{S}}_{kB}^2\cup \left\{S_i\right\}$ ;

5:        else

6:                ${\mathbb{S}}_{kB}^1$ = ${\mathbb{S}}_{kB}^1\cup \left\{S_i\right\}$ ;

7:        end if

8: end for

9: return ${\mathbb{S}}_{kB}^1$ and ${\mathbb{S}}_{kB}^2$;