Algorithm 1 The MU association matching algorithm.

Initialization phase:$L=⌈\frac{K}{NF}⌉$, $\widehat{\mathcal{K}}=\mathcal{K}$

1: for $l=1:L$ do

2:  $\widehat{\mathcal{M}}=\mathcal{M}$, $Count=1$

3:  while ($Count\le M$) do

4:   $H_{k^{*}{f}^{*}{n}^{*}}=argmax{\left\{H_{kfn}\right\}}_{\forall k\in \widehat{K},(f,n)\in \widehat{M}}$. Assign $k^{*}$ to the couple $(f^{*},n^{*})$, $\widehat{\mathcal{K}}=\widehat{K}\backslash k^{*}$, $\widehat{\mathcal{M}}=\widehat{\mathcal{M}}\backslash (f^{*},n^{*})$, and set $Count=Count+1$

5:  end while

6: end for   Swap matching phase: $Indicator=1$

7: while ($Indicator$) do

8:  for $u=1:K$ do

9:   for $k=1:K$ do

10:    if $\mathsf{\Psi }\left(k\right)=\mathsf{\Psi }\left(u\right)$ then

11:     continue;

12:    else if ${\mathrm{MU}}_k$ and ${\mathrm{MU}}_u$ are both in the coverage of the BSs of each other then

13:     switch ($\mathsf{\Psi }\left(k\right),\mathsf{\Psi }\left(u\right)$)

14:     case ${\mathrm{MU}}_k$ and ${\mathrm{MU}}_u$ belonging to the same BS and different sub-channels:

15:      Calculate and compare the EE of the two sub-channels before and after the swap using the power control algorithm. If the EE of the two-subchannels both improve, exchange the sub-channel, form the new couple, and set $Indicator=1$.

16:     case ${\mathrm{MU}}_k$ and ${\mathrm{MU}}_u$ belonging to the different BSs and different sub-channels:

17:      Calculate and compare the EE of the two sub-channels before and after the swap using the power control algorithm. If the EE of the two sub-channels both improve, exchange the couple, form the new couple, and set $Indicator=1$.

18:     case ${\mathrm{MU}}_k$ and ${\mathrm{MU}}_u$ belonging to the different BSs and same sub-channels:

19:      Calculate the EE of the sub-channel before and after the swap using the power control algorithm. If the EE of the sub-channel has been improved, exchange the BS, form the new couple, and set $Indicator=1$.

20:      end switch

21:     end if

22:    end for

23:   end for

24: end while