Software-Defined Networking in wireless ad hoc scenarios: Objectives and control architectures

While SDN has traditionally targeted fixed and wired environments with hundreds of nodes, recently its main principles have also been followed in wireless ad hoc scenarios. However, node mobility and heterogeneity characterizing such dynamic scenarios prevent the adoption of purely centralized control solutions, pushing for more articulated and distributed architectures. We provide a thorough analysis of state-of-the-art literature related to the adoption of SDN in wireless ad hoc scenarios, ranging from WSNs with mostly fixed sensors and WMNs with mobile clients but stable routers to MANETs with every node freely moving on the field, VANETs with vehicles speeding through the network road, and FANETs with aerial vehicles flying in every direction. For each identified wireless ad hoc scenario, we present the rationale behind the adoption of SDN, recognizing that the objective of the SDN controller is far beyond mere routing management in such challenging scenarios. Furthermore, we detail the proposed control architectures, showing how the peculiar characteristics (and related goals) of a given scenario influence the architecture design. Finally, we point out hybrid control architectures as a notable trend in SDN solutions targeting wireless ad hoc scenarios.