## 3 Heterogeneous Network Model of the Proposed Models
### SDN-Enabled Iteratively Reconfigurable WSNs of the Proposed Models  
The iterative architecture of SDN-IRWSNs consists of OpenFlow-enabled sensor nodes deployed at the infrastructure layer, while these sensors are connected to the SDN central controller, which resides at the Base Station (BS). The number of sensor nodes varies according to the required applications, and similarly, SDN-IRWSNs can be extended to utilize multiple SDN controllers. The basic architecture of SDN-IRWSNs is shown in Figure 2. The left side of Figure 2 indicates the protocol stack, while the right side indicates the SDN-IRWSN architecture's layers and associated components. The infrastructure layer consists of sensor nodes, and these planes utilize the protocol stack of forwarding logics, while each sensor consists of multiple sensing components of environmental parameters. These sensor nodes have a Micro Controller Unit (MCU) with limited computational capacity powered by the Power Unit (PU) and Sensing Unit (SU). All the attached components are powered by PU to operate their circuitry. These sensor nodes include IEEE 802.15.4 transceivers for wireless communication with the central controller at BS. Forwarding (FW) layers deal with packet forwarding activities by adjusting forwarding tables for information received through IEEE 802.15.4 transceivers containing Receiver Transmitter (RT). These forwarding tables are dictated by control layer components that include single or multiple SDN controllers according to network scalability.  
\begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Management** & **Energy** & & & & & \\
**Architecture** & **Efficiency** & & & & & \\  & & & & & & \\ \hline SDN-WISE [5] & ✓ & ✓ & ✓ & & & \\   SDCSN [27] & ✓ & & & ✓ & ✓ & ✓ \\ Sensor OpenFlow [28] & ✓ & ✓ & & & & \\   Soft-WSN [12] & ✓ & & ✓ & & ✓ & \\ TinySDN [29] & ✓ & & ✓ & & & ✓ \\ TinySDM [30] & ✓ & ✓ & ✓ & & & ✓ \\ SDWN [32] & ✓ & & & & ✓ & ✓ \\ ATCEEC [17] & ✓ & & ✓ & & & \\   MCEEC [16] & ✓ & & ✓ & & ✓ & \\ SACFIR & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ \\ SAMCFIR & ✓ & ✓ & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table}
Table 1: SDN-based sensor network and topology management architectures. WISE, WIreless SEnsor.  
Similarly, at the protocol stack level, the Inter-Networking Processing (INP) protocol guides the path selection of the forwarding mechanism. Inter-Networking Processing (INP) is responsible for the path selection process, and routing decisions implemented on the SDN controller are executed here to define the routing tables. In this paper, we propose two routing policies, SACFIR and SAMCFIR, which are implemented at the INP level. In order to create an efficient forwarding table at the infrastructure layer, the SDN controller hands over some key network statics to the application layer to make the routing decisions, and this key information is obtained through the topology discovery layer. The control layer sends existing routing, flow-table and topology information to the application layer by SACFIR-Visor. SACFIR-Visor supervises the collected information sent to the application layer APIs and waits for feedback. The application layer APIs are programmable by the network administrator to respond according to the network conditions. Then, SACFIR-Visor ensures that the SDN controller implements the received response.