# An Integrated Cognitive Radio Network for Coastal Smart Cities
## 2 Integrated Cognitive Hybrid Communications for a Coastal City  
An integrated cognitive radio coastal city which can fulfill the service demands of citizens in less response time is shown in Figure 1. The objective of this proposed architecture is to reckon with key issues in different types of current applications that consider different communication systems. We designed an integrated coastal city to serve citizens with different application demands within an all-in-one framework. For the current work, we combined terrestrial and marine applications to make an integrated coastal city. The terrestrial network includes vehicular applications. The fog cloud functions as the local cloud by serving as a central entity near the edge users to provide stable links between users on ships and in vehicles. Two types of application services were launched by the NFV hypervisor: vehicular applications and maritime applications. The launched virtual functions were monitored and controlled by an SDN controller. The SDN controller is also responsible for connectivity among these launched virtual functions. It keeps the global updated network topology of both networks by communicating with the local controllers (LCs) of each network. The LCs, which are roadside units (RSUs) and ships near the shore, keep the local updated topology of the corresponding network. For marine communications, we assumed a ship moving close to shore was an LC. A border gateway (BG) was used to communicate between the two different networks. Like the LCs, the BG is in direct communication with the SDN controller. Our objective was to provide hybrid, as well as pure, communications between the vehicular and maritime networks by using an integration of SDN, NFV, and FC. For hybrid vehicle-to-ship (V2S) communications, the BG is used to provide connectivity between the two different environments, and the SDN controller is responsible for maintaining connectivity among the different VNFs. However, for vehicle-to-vehicle (V2V) or ship-to-ship (S2S) communications, the corresponding VNF provides the service to meet the users' demands. With either hybrid communications or pure communications, the fog cloud acts as a local cloud to provide flexibility and preserve latency. Accordingly, whenever an LC receives a service request message (SRM), it first examines its forwarding table to determine whether it can provide a path that fulfills the user's demand. If so, it sends the service provision message (SPM). Otherwise, it forwards the request to the SDN controller which, if it does not find the required service in its forwarding table, communicates with the VNFs to meet the user's demand. If the SDN controller does not find the respective VNF, it sends a request to the NFV hypervisor to launch the respective VNF. Figure 2 shows the flowchart for different communications with integrated technologies. As this is a cognitive coastal city, we assumed that primary users were located across the lanes and the seashore, as shown in Figure 1. For that reason, a car can only communicate with the LC and with its neighboring cars if there is at least one common free channel between the two communicating nodes. Similarly, ships only communicate with their LC and with each other if there is a common channel free from PU activity between the two. The integration enables different users from different applications to be served at the same time. In the following, we explain in detail how a source node (either vehicle or ship) selects the best path by discussing the pure, as well as hybrid, communications using our example integrated cognitive coastal city scenario. In Figure 1, a vehicular source-destination pair is looking for a stable route to communicate with each other. The source car asks the LC to provide a stable route. The LC provides the route either from its forwarding table or after receiving it from the SDN controller. At the same time, a source ship  
Figure 1: Integrated cognitive coastal city. at sea requests a route for a destination.