# Enhancing Heterogeneous Communication for Foggy Highways Using Vehicular Platoons and SDN
## 3 Proposed Scheme: SDVN for Foggy Highways  
To overcome the adverse weather effect while driving, we propose a platoon-based communication system in SDVN, as shown in Figure 1. The MC is considered a dedicated infrastructure (such as a toll booth, a motorway police office, or a parked motorway police car) in a highway scenario to monitor the overall network traffic. We will consider the city scenario in the near future. The RSUs (such as street lights, cameras, or sign boards) act as LCs to share the network traffic load of a single MC. Not all RSUs are LCs, otherwise our aim of proposing an optimal routing path would fail. Our objective is to reduce delay and overhead in a foggy environment by ensuring connectivity, which is why only a few out of all RSUs serve as LCs. As a result of this division, the MC and LCs are responsible for managing network traffic at both the global and local levels, respectively. DSRC technology is used by vehicles within the platoon to communicate. If inter-platoon communication is not possible using DSRC due to distance, LCs are used as relays, as can be seen in Figure 1.  
Considering a foggy environment on roads with very limited visibility, in this work, we consider different cases for handling network traffic with safe and stable communication links. These communication links then form an optimal routing path between any source and destination by exchanging current status information (such as vehicle ID, position \((x,y)\), velocity (_vel_), current visibility (_visc_), and current time (_t_)) with each other and with any LC within their communication range. Similarly, the head vehicle (HV) of the platoon is responsible for exchanging the collected data from its platoon to those heads that are within the communication range of this platoon. By doing so, a stable path between platoons is created, which enables any source vehicle in a trailing platoon that is far away from the destination vehicle in a leading platoon to determine the current visibility status at the destination location. In a sequence of platoons traveling along the same route as shown in Figure 1, the leading platoon is the platoon that is at the front, while the platoon that trails the leading platoon is called the trailing platoon. A question may arise for the reader as to who makes the selections for the LCs and who makes the decisions for the HV in a platoon. The answer for both is the MC. We use DTC to locate the LCs at each level on the road. DTC is used because RSUs are placed at various levels on the road, producing a tree-based topology where MC is the parent node, and all remaining RSUs are the child nodes. The parameters we consider are the distance of each RSU from the MC, the number of hello messages received per second to count connectivity, and the number of hops required to reach the MC (see Figure 2). Based on  
Figure 1: A machine learning SDVN model for foggy highways. these parameters, we choose the LC with the minimum delay (\(MD\)) at each depth of the tree as  
\[MD_{controller}=(\frac{d_{MC,i}}{\alpha\times speed}+\frac{L_{s}}{R \alpha,i}+\frac{t}{HM})HC, \tag{1}\]  
where \(d_{MC,i}\) indicates the Euclidean distance between MC and each \(i\)th RSU, \(L_{s}\) is the packet size, \(R_{MC,i}\) is the rate (\(bps\)) of each link, \(t\) is the current time, \(HM\) is the amount of hello messages received periodically from vehicles within communication range of each \(i\)th RSU, \(HC\) is the number of hops that are counted to reach the MC, a constant \(\alpha\) is used for a balance, and \(speed\) is the speed of light since we assume that the communication links between MC and RSUs are LTE-based. Each RSU calculates its \(MD_{controller}\) from the MC, which takes into account the distance (\(d_{MC,i}\)) from the MC, the number of hops (\(HC\)) needed to get there, and the density of vehicles at the time \(t\). If the \(MD_{controller}\) value is lower, the number of hops will be lower, and the density of vehicles will be higher.