SACFIR: SDN-Based Application-Aware Centralized Adaptive Flow Iterative Reconfiguring Routing Protocol for WSNs  
[PERSON]  
1 School of Computer Science and Technology, Dalian University of Technology, Dalian 116000, China;  
reconfigurations offer theoretically better Quality of Service (QoS), but they also demand global knowledge of the network topology and other available resources [3; 5; 6; 7]. The existing challenging task of ensuring the commercial success of WSNs needs attention from researchers to provide real-time installation and establish adaptive reconfigurable management. The proposed application-specific requirements of network operators demand flexible networking scenarios and the ability to recycle the limited network resources. Recent research on WSNs highlights some solutions to deal with the challenges encountered by introducing central management and control of network reconfigurations [8; 9]. These solutions mainly focus on channeling programmable sensor devices. These ideas have revolutionized the reconfigurations of WSNs, and extensive industrial- and academic-level ideological experiments have shifted towards this. Central management and reconfiguration control of the Software-Defined Networking (SDN) paradigm and OpenFlow currently comprise the most popular instance of SDN. SDN has fundamentally evolved to bring the control plane to the central controller and impose the reconfigurable forwarding plane by installing centrally-programmable forwarding tables on network devices. Networking layer utilizes different modules like Access List (ACL) module for establishing forwarding tables. The basic centrally-oriented architecture of SDN is shown in Figure 1. Since practical solutions for central management of SDN penetration in wired and wireless enterprise networks have been developed, researchers have achieved a breakthrough in introducing similar SDN-based central management to WSNs. This provides the capability to shift complicated control logics like topology discovery, residual resource computations and path-selection to route the sensed reports from sensor nodes to the SDN central controller. Limited battery-oriented sensor nodes save a significant amount of energy by the replacing the control plane computation and only being responsible for the forwarding plane. Although nodes still have the burden of reconfiguring the forwarding tables on the iterative reconfiguration period, they save a significant amount of energy due to the absence of the control plane [8; 9]. SDN-based iterative reconfiguration of WSNs is more suitable for energy-efficient cluster-based vertical reorganizations of network nodes into Forwarding Element Cluster-Heads (FECHs) and non-Forwarding Element Cluster-Heads (non-FECHs). The SDN central controller develops routing policies for horizontally-separated control from the data planes and equally redistributes the responsibilities of FECHs and non-FECHs. Therefore, the control plane optimizes the data-handling  
Figure 1: Architecture of Software-Defined Networking (SDN). decisions, whereas the data plane forwards data according to the routing decisions of the control plane. Major clustering protocols emphasize developing the required standard energy-efficient features of iterative reconfigurations, including application-specific, rate adaptation and powering down approaches [10; 11; 12; 13; 14; 15]. Rate adaptation results in the energy consumption reduction of networks by scaling the power consumption of a network element to the amount of traffic it carries. The power down approach conserves energy by switching off unused network elements, which operate either at the full rate or zero rate [4; 16; 17]. However, often, iterative reconfigurations degrade QoS for classical WSNs and introduce inertia into the system because application-specific sensing, rate adaptation and speed scaling create an overhead of intensive packet exchange between sensor nodes and the central controller at the BS.