## 2 Related Work  
Several researches have shown that position-based protocols are the most appropriate for VANETs [15]. In these protocols, the routing of information from source to destination is based  
Figure 1: Video streaming applications over vehicular network [7]. on choosing the closest vehicle to the destination as the next hop. In the geographic routing protocols, the choice of the next-hop relay vehicle influences the quality of received information. Many studies proposed various improvements to GPSR by using other information in addition to the position in the routing process. In these improvements, some researches consider the speed and the direction to estimate the distance in the next forwarding node selection process [16; 17]. Others used predicted positions based on speed and direction [18; 19; 20]. Some studies introduced other factors as link lifetime [21], link reliability [22], link available time [23], link state [24], road density [25], buffer size [26], and social attributes [27]. Furthermore, the weighted numerical functions of many factors are used in [28; 29]. The store and forward mode is used as an alternative to the perimeter farwarding in [30]. The selection of two different relays to forward information in order to enhance QoE has been proposed in [14]. Geographic protocols use various techniques and mechanisms in the routing process. Geographic source routing (GSR) is intended for use in urban scenarios [31]. In GSR, the source vehicle calculates the shortest path to the destination based on the street-map. On this path, it selects the sequence of intersections through which the data packet must be routed. Cross-layer weighted position-based routing (CLVPR) uses the prediction of the node's position, the navigation information and the quality of the links in the next-hop selection [32]. In CLVPR, links quality is estimated based on the SNIR (signal to noise-plus interference ratio) value and MAC frame error rate. This information is combined into a weighted function to obtain the weight of all neighbouring vehicles. Link state aware geographic opportunistic routing protocol (LSGO) combines the geographic location and the link state information as the routing metric [33]. In this protocol, link quality is measured using the enhanced expected transmission count (ETX) metric. Moreover, some topology-based protocols use the location in their routing mechanism. Location aided routing protocol (LAR) is an on-demand routing protocol [34]. It uses vehicles location information to decrease the routing overhead. The flooding mechanism is used in a restricted area called \"request zone\" during route discovery. The route request packet for a destination in LAR is flooded in this zone instead of the whole ad hoc network. GEOADV is a hybrid protocol which combines both reactive and geographic routing [35]. Routes from the source to the destination are created reactively. In path construction, an intermediate vehicle is chosen in the path if it maximizes the path weight. The vehicle's weight is computed by a numerical formula including speed, movement direction and link quality. In these mentioned protocols, video services are not considered in the routing mechanism. Few protocols are designed to manage video streaming. Video reactive tracking-based unicast protocol (VIRTUS) is a geographic routing protocol dedicated for video streaming in VANETs [36]. It uses the vehicle's predicted state (position, velocity and bearing) and the maximum waiting time in the relay selection process. 3 MRP is a geographic multimedia multimetric map-aware routing protocol based on hop-by-hop forwarding decisions in a smart city [37]. The next-hop selection is based on a weighted numerical function of the distance to the destination, vehicles density, trajectory and available bandwidth. It uses the map to avoid sending packets to vehicles behind buildings. In the discussed related litterature, routing decisions can not satisfy the video services requirements.