## 3 QoE-Aware Geographic Routing Protocol for Video Streaming over VANETs  
The GeoQoE-Vanet is a QoE aware geographic routing protocol for video streaming over VANETs, based on the selection of the best next forwarding vehicle from the neighbours of the current vehicle. The information used in the selection decision is collected by vehicles where each one records its state information, stores it locally and broadcasts it in beacon messages to surrounding vehicles. When a vehicle receives a beacon message, it inserts or updates the entry of the beacon sender vehicle in the neighbours' table. The factors used in the proposed protocol are position, direction, speed and link expiration time as mobility factors, and packet loss rate, delay and jitter as QoS factors to estimate the vehicle's MOS (\(MOS_{routing}\)). When a vehicle decides to send a video to a destination, it first selects the best forwarding vehicle based on information stored in its neighbours' table, then sends the video information to the selected vehicle. The selected vehicle resends the received video data to another vehicle in the same manner and this process is repeated until reaching the destination. An example of a vehicle neighbours' table is shown in Table 1. Figure 2 shows the selected relay vehicle based on the proposed next-hop selection mechanism. In this example, the vehicle 28 is selected by the source \((S)\) despite the fact that it is not the closest to the destination \((D)\). However, it ensures, better than other neighbours of \((S)\), the perceived video quality. When the state of the sender's neighbours does not satisfy the QoE requirement and there is a risk of packet loss, a second different relay is used to send the same packet as proposed in the previous paper [14]. In the proposed protocol, only vehicle to vehicle(V2V) communication is used and the data is forwarded between vehicles without using the infrastructure to vehicle (V2I) communication. Figure 2: Next hop selection strategy in GeoQoE-Vanet protocol. The beacon message used in GeoQoE-Vanet is the usual beacon packet employed in vehicular networks. It is periodically droackasted by each vehicle. It has been slightly modified by adding information needed by GeoQoE-Vanet as depicted in Figure 3.  
Each vehicle records its delay, jitter and packet loss rate. Before sending a beacon, it estimates its \(MOS_{routing}\) then inserts it in the beacon message. In this protocol, the mobility factors are used to predict the future position and the link quality of all vehicles in the vicinity during the selection phase of the next relay. The rest of this section is devoted to the presentation of the quality factors used in the proposed protocol, the developed correlation formula of these factors and the mechanism of the next-hop selection. For the remainder of this paper, the adopted notations are presented in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Vehicle-Id** & **Position (x, y)** & **Direction** & **Velocity** & \(MOS_{routing}\) & **Timestamp** \\ \hline
25 & 6520.72, 2324.830 & 0 & 13.06 & 2.63 & 23.87 \\
28 & 6620.81, 2363.39 & 0 & 4.47 & 3.53 & 24.94 \\
66 & 6305.33, 2437.66 & 0 & 7.99 & 1.96 & 24.35 \\
88 & 6458.77, 2291.84 & 0 & 13.16 & 2.65 & 24.04 \\
123 & 6569.16, 2233.75 & 0 & 0.00 & 2.63 & 22.24 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Vehicle neighbours’ table in GeoQoE-Vanet.