# Video Streaming in Urban Vehicular Environments: Junction-Aware Multipath Approach
## 3 Junction-Aware Vehicle Selection Scheme
### Information Exchange Phase  
At the information collection phase, every vehicle exchanges a hello message with its neighbor vehicle. The hello message (HM) is exchanged within a time interval of every second. The HM content includes the vehicle direction, position, ID, road-ID and hello message time-stamp. The generated hello messages are stored in a Neighbor Information Table (NIT). The NIT is updated in every time interval of the hello message exchange; that is, one second. The parameters in the NIT are recorded based on tuple since the collections of items are different. The position is based on x, y coordinates, which are centered on relative distance. The road-ID is simply an identifier which is alphanumeric. The time stamp is recorded in seconds. The direction is based on four cardinal directions including north, south, west and east. The vehicle-ID is recorded based on an alphanumeric identifier. The information packet format is depicted in Figure 2. The direction and position are estimated using the GPS of each vehicle, which is employed to determine the location of the vehicle in the junction area. The road-ID is used to determine if the vehicle is on the new road and is employed for the vehicle selection at the junction area. A linked list is used to store packet information, as the sizes of each element are different, with standard units considered such as milliseconds for time stamps, latitude and longitude with six-digitdecimal points, etc. In addition, the selection considers the quality of the vehicle signal based on the signal to interference plus noise ratio (SINR), as formulated in Equation (1), before considering the three cases in the junction area. In addition, the vehicle density at the junction has been considered for suitable candidate vehicle selection, which is shown in Equation (2). In the generic concept of the geographic routing, the Source Vehicle Node (SVN) is already conscious of the direction and location of the DVN in the network based on the location service system and GPS. Therefore, the greedy algorithm is adapted in a way that not only selects the vehicle closer to the destination but also takes into account the aforementioned three different cases of the junction area. \[SINR_{(p_{i},p_{j})}=\frac{S_{PW}F_{RD(p_{i},p_{j})}\times I\left(p_{i}-p_{j} \right)}{\varphi+\sigma\left(p_{j}\right)} \tag{1}\]  
where \(p_{i}\) is the sender vehicle's position and \(p_{j}\) is the signal receiver vehicle's position. Thus, \(S_{PW}\) is the transmitting signal strength, and \(F_{RD}\) is the random fading between the sender vehicle and the receiving vehicle. In addition, \(l\) is the distance between \(p_{i}\) and \(p_{j}\), while \(\varphi\) and \(\sigma\) denote the external noise and small short-noise of \(p_{j}\), respectively. We have considered one direction; that is, the directions of travel of the sensor and receiver vehicles are the same. Here, it is noteworthy that the proposal will also work for the two-dimensional scenario; that is, the directions of travel of the sender and receiver vehicles could be different or in opposite directions. However, in this case, the computation will be somewhat impacted by the speed of vehicles. Consequently, both the distance and SINR are employed when selecting a vehicle in the junction area. The vehicle density is estimated as  
\[ VDR=\frac{\left(3\times IDVD\right)+ODVD}{4\times 2 Hop} \tag{2}\]  
The next forwarding vehicle is selected based on the Candidate Next Forwarding Vehicle (C-NFV) which has the highest value of Vehicle Density of the Road (VDR). However, the Opposite Direction Vehicle Density (ODVD) is given a smaller value by multiplying it with \(\frac{1}{4}\), which is three times lower than the value of the In-Direction Vehicle Density (IDVD) multiplied by \(\frac{3}{4}\). This is because the vehicles moving in the opposite direction are considered not to have longer or continuous connectivity with the forwarding vehicle. This ensures that a C-NFV moving towards the direction of the DVN is given higher priority.