Sites e serviços pertencem principalmente à replicação e diferentes sites físicos :
In your physical network, a site represents a set of computers that are connected by a high-speed network, such as a local area network (LAN). Typically, all computers in the same physical site reside in the same building or perhaps the same campus network.
In AD DS, a site object represents the aspects of the physical site that you can manage, specifically, replication of directory data between domain controllers. You can use Active Directory Sites and Services to manage the objects that represent the sites and the servers that reside in those sites.
Portanto, não seria necessário adicionar outra sub-rede para sua conexão sem fio.