Algorithm 1: Subcarrier scheduling and user pairing scheme.
1:	Input:$N_c$, U, ${\left|l_{n_c,k_{n_c}}\right|}^2$, $P_{1,n_c}$ and $P_{2,n_c}$.
2:	Output: Subcarrier mapping $\vartheta$ and user pairing $k_{n_c}$.
3:	Initialize: $n_c=0$ and $i=1$, where i denotes the ith element of ${\mathbb{U}}_s$;
4:	while$n_c\in [0,N_c-1]$do
5:	while $i\in [1,U·(U-1\left)\right]$ do
6:	Select the ith element of ${\mathbb{U}}_s$;
7:	Determine the $1_{n_c}$th and $2_{n_c}$th users;
8:	Calculate $E_{\mathrm{total}}$ as (16);
9:	Record $E_{\mathrm{total}}$, subcarrier scheduling $\vartheta$ and user pairing $k_{n_c}$;
10:	$i=i+1$;
11:	end while
12:	$i=1$;
13:	$n_c=n_c+1$;
14:	end while
15:	Search the maximum $E_{\mathrm{total}}$ and corresponding subcarrier scheduling $\vartheta$ and user pairing $k_{n_c}$.