# A Load Balancing Routing Mechanism Based on SDWSN in Smart City
## 2 Related Work  
In [9], it is proposed that traditional sensor networks are inflexible due to over-reliance on proprietary services, so data and control separation modes are suitable for wireless sensor networks. They also point out the challenges of this wireless sensor network combined with software-defined networks, as well as the necessary basic design load balancing requirements. In [10], a new mobile network architecture based on OpenFlow to achieve centralized control of energy-aware on demand for load balancing is proposed. In [11], the research results of the software-defined wireless sensor network into actual hardware systems are translated. The OpenFlow switch built a software-defined wireless sensor network platform and runs a traffic-aware routing algorithm on it. The Open DayLight cluster can accurately analyze the data. The flow direction in the network proves that the traffic-aware routing algorithm can improve network utilization and reduce controller response time. Although these new WSN architectures can solve some of the problems of traditional WSN, we should also see that the resource allocation design of software defined wireless sensor networks is not perfect and the research on load balancing needs to be further improved.  
In [12], they propose a QoS-based multi-path routing protocol in SDN. In order to meet the QoS requirements of network applications, this protocol designs a multi-path routing protocol based on SDN, which significantly improves the utilization rate of idle resources in the search space. In [13], they present a unified multi-layer architecture with multiple controllers and a dynamic orchestra plane for software defined multi-domain optical networks. In [14], a framework for multi-layer; multi-vendor optical network management using open standards-based SDN is proposed. In [15], a routing algorithm based on SDN technology is proposed, which is used for a routing calculation between AS (Autonomous Systems). The above documents, in the SDWSN network architecture, can solve some unsolved problems of traditional routing protocol, but cannot respond in real time and be dynamic in the aspect of load balancing of traffic.  
In [16], a new control system based on the integration of SDN and IoT in smart city environments is proposed. This control system actuates when an emergency happens, modifies dynamically the routes of normal, emergency urban traffic in order to reduce the time that the emergency resources need to get to the emergency area. In [17], a novel routing protocol applied SDN in wireless multi-hop network is proposed. The routing protocol provide a shortest path, disjoint multipath routing for nodes, and its network lifetime is longer. In [18], they highlight the application challenges faced by wireless sensor networks for surveillance environments, those faced by the proposed approaches, as well as opportunities that can be realized on applications of SDWSN. In the SDWSN network architecture, the above literature focuses on the special functions that should not be ignored when trying to improve the network function, however, the load balancing design of the traffic is insufficient.  
In summary, the research results of the routing protocols in the classic wireless sensor networks have been quite abundant. The software-defined routing protocols for new network architectures have also achieved preliminary research results. However, the software defined wireless sensor network technology is still immature and needs to be explored and studied in many aspects. It is of great significance to conduct in-depth research on its routing protocols.