Algorithm 1 Dynamic Group Matching Algorithm.

1:Initialization: Initialize the matched pairing set of the UEs and relays $\Phi =\varnothing$, the unmatched set of the UEs and relays $U\_UE$, $U\_RE$, and initialize the matching priority sets of the UEs and relays $\{MP\_UE\}$, $\{MP\_RE\}$ through the Equations (20) and (21) 2:while $U\_UE\ne \varnothing$ do 3:   Each UE in $U\_UE$ requests to match its highest matching priority relay from $U\_RE$ according to the matching priority set $\{MP\_UE\}$ 4:   for relay m = 1, 2,…, M do 5:      Each relay matches the UE with the highest priority according to the matching priority set of relays $\{MP\_RE\}$ and rejects the other UEs 6:      The rejected UEs remove the mth relay from its matching priority set $\{MP\_UE\}$ 7:      Add the matched paring $\Phi (m,n)$ to the set $\Phi$ and remove the mth relay and nth UE from $U\_RE$ and $U\_UE$, respectively 8:   end for 9:end while 10:while$\{MP\_UE\}\ne \varnothing$ or $U\_RE\ne \varnothing$ do 11:   Each UE requests to match its highest matching priority relay from $U\_RE$ according to the updated set $\{MP\_UE\}$ 12:   for relay m = 1, 2,…, M do 13:      The mth relay makes the following judgment for its highest matching priority UE according to its matching priority set $\{MP\_RE\}$ 14:      if ${\sum }_{m=1}^M|\Phi (m,n\left)\right|<Q$ then 15:         Add the matched paring $\Phi (m,n)$ to the set $\Phi$ and remove the mth relay and nth UE from $U\_RE$ and $U\_UE$, respectively 16:      else 17:         The relay matches with the nth UE when there exists a relay that satisfies ${\psi }_{mn}>{\psi }_{ln}$ and $|\Phi (l,n\left)\right|=1$; then, it updates $\Phi$ and removes the lth relay into $U\_RE$ 18:         Otherwise, reject the matching request of the nth UE and remove the mth relay from its matching priority set $\{MP\_UE\}$ 19:     end if 20:   end for 21:end while