node can be connected to each sub-network. In all following rounds, the identified RNs and sub-networks which have not been selected in previous rounds become the vertices. And the convex polytope is again calculated to determine the respective border sub-networks and new RNs are obtained in a new round. This step is circulated until the considered vertices can connect to the Base-station. 2) Secondly, the selected RNs are for sub-networks and Base- station connection and the selected candidate nodes are for inter-sub-network 2-connected topology with the optimal total number of the RNs placement. And the main processes are described in the next subsection.