# Software Defined Networking for Improved Wireless Sensor Network Management: A Survey
## 6 Discussion  
In this review, several contributions to management of WSNs based on SDN have been made. It can generally be concluded that the overall SDN-based management of WSNs be looked at as being developed around the north bound, east-west bound and south bound abstractions of the SDN \begin{table}
\begin{tabular}{c c c c} \hline \hline
**OS** & **Language** & **Memory Management** & **Implementation for** \\ \hline TinyOS & NesC & Static & TinySDN [69; 118], TinySDM [117], mobility [101] \\ Contiki & C & Dynamic & SDN-WISE [135] \\ MANTIS & C & Dynamic & - \\ Nano-RK & C & Static & - \\ LiteOS & Lite C++ & Dynamic & - \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Enabling node operating systems for SDN-based management of WSNs: A comparison. architecture. These are classified based on the location of the management control referred to as the manager. Figure 5 below illustrates this management view. East-West bound management can further be looked at as central management, several proposals have been made towards improving management of control plane functions. Core to the function of SDN-based management of WSNs is the network configuration and topology management. Managing how the network operates efficiently and how nodes in the data plane communicate with the controller nodes and peripherals is the goal of developing a network configuration and topology management architecture. Soft-WSN an architecture based on East-West management has been proposed and tested by [PERSON] et al. [9]. Soft-WSN is a software defined WSN management system for IoT providing an application-aware service consisting of an application, control and data layers. The architecture is based on centralized device (enabling hardware) and network configuration policies provisioned on the controller design. Experimental results on Soft-WSN show an enhanced energy efficiency, traffic overhead and data delivery ratio in a network [9]. To ensure SDN integration in WSNs, proposals such as Sensor OpenFlow, SDWN and SDN-WISE techniques which provide solutions to designing and managing WSNs based on SDN in terms of flow setup, in-network data processing and traffic management and general management of flow rules have been made. In managing the topology Smart, SDCSN and TinySDN provide an efficient high-level architecture resulting in efficient resource allocation. However, Smart does not provide for distributed controllers compared to SDCSN and TinySDN posing a greater risk in system security and reliability once the base station controller in Smart comes under attack. The network virtualisation demonstrated in the virtual overlay topology introduces greater flexibility in managing and monitoring networks. In managing localization of nodes, localization algorithms have been proposed to improve the accuracy of locating nodes. [PERSON] et al. [100] for example present a localization algorithm that does not only improve the performance of the localization but also conserve energy which is a vital component when designing and managing WSNs based on SDN. In tandem with management of node localization is mobility management which takes into account the movement of nodes into and out of the network. An attempt at managing mobility has been made by [PERSON] et al. [87] outlining the steps for handling node mobility in and out of a SDWSN however, there is room for research in SDN-based management of node mobility. Figure 5: SDN-based management abstractions for WSNs. In terms on communication management, the importance of using multi-hop techniques in an energy constrained network has been emphasised. As data is carried and passed on from node to node, less energy is required and it also allows for data aggregation which reduces redundancy in the network. The challenge with this for enabling SDN-based management is the requirement for communication between the global controller and the nodes on the network as it may happen that a link may break once any of the nodes acting as repeaters falls out of the network.