transmission between any two sub-networks. That is how to add RNs to cover one or more fixed agency node in each sub- network, and then connect all the sub-networks. Moreover, the number of required RNs should be minimized. This issue has been proved that is a NP-hard problem [16]. Additionally, there is only one agency node for each sub-network, and the sub- networks traffic is transmitted via the identified agency nodes. A RN is placed and close to agency node, in order to share potentially high traffic with agency node. And the RNs placement has to satisfy the network fault tolerance requirement.