## 4 Numerical Results and Discussion
At the required \(\textit{SINR}_{\text{th}}\) of 20 dB, which is considered the high system requirement, it can be seen that the transmission power (\(P_{V}\)) is 17 dBm, the distance between AV2X is 200 m, and the required position between the relay-vehicle and the destination is 12.5 m. Conversely, when the transmission power is 23 dBm, the relay-vehicle position is 20 m. On the other hand, when the required system performance decreases, the relay-vehicle position from the destination increases, e.g., when \(\textit{SINR}_{\text{th}}\) is 0 dB, the transmission power is 17 dBm and 23 dBm and \(d_{AVX}\) is 200 m, then the relay-vehicle position between AV2X is 57.7 m and 94.22 m, respectively. The obtained results show that the required system QoS affects the position of the relay-vehicle when needed, as decreasing the distance between relay-vehicle and the destination decreases the packet loss due to the channel conditions. The best relay-vehicle position is examined again versus different signal-to-interference-plus-noise threshold (\(\textit{SINR}_{\text{th}}\)) for transmission distance between AV and X equal to 100 m and with two different AV and vehicle transmission power. In this scenario, it is assumed that the system suffers from high interference which means that all the devices sharing the same spectrum have maximum transmission power. Thus, it can be demonstrated from Figure 4 that increasing the vehicle transmission power leads to the relay-vehicles being far from the destination, regardless of the value of the required \(\textit{SINR}_{\text{th}}\). Additionally, it can be noticed that increasing the required \(\textit{SINR}_{\text{th}}\) leads to a decrease in the distance between relay-vehicle and the destination, regardless of the value of the transmission power. It can be noted from Figure 4, when \(P_{V}\) is 17 dBm and the required \(\textit{SINR}_{\text{th}}\) is 20 dB, that the best relay-vehicle position from the destination (\(d_{V1X}\)) must be 3.247 m in order to fulfill the required system performance, while when \(P_{V}\) is 23 dBm, the position of the relay-vehicle must be 5.277 m from the destination. On the other hand, when the required \(\textit{SINR}_{\text{th}}\) is 0 dB and \(P_{V}\) is 17 dBm, the distance between relay-vehicle and destination (\(d_{V1X}\)) is 15.37 m, while when \(P_{V}\) equals 23 dBm, \(d_{V1X}\) is 24.51 m. Therefore, it can be concluded from this  
Figure 3: Distance between AV2X vs. best relay-vehicle position. figure that the required \(SINR_{th}\) plays an important role in deciding at what distance the relay-vehicle should be located from the destination. Furthermore, Figure 5 depicts the best relay-vehicle position versus vehicle transmission power. Assuming that \(d_{AVX}\) is 100 m andtwo different \(SINR_{th}\), the system experiences high interference. Then, under these conditions, it can be mentioned that increasing the vehicle transmission power increases the required distance between the relay-vehicle and destination. As can be noticed from Figure 5, when \(SINR_{th}\) is 0 dB and \(P_{V}\) is 23 dBm, the best position relay-vehicle must be located at 24.71 m from the destination; conversely, if \(P_{V}\) is 0 dBm, the relay-vehicle should be at a distance of 4.258 m from the destination. Furthermore, increasing the \(SINRth\) with high interference leads to the need for the relay-vehicle to be located near the destination to try to overcome the interference and fulfill the QoS requirement, e.g., when \(SINRth\) is 20 dB and \(P_{V}\) is 23 dBm, the distance between the destination and the relay-vehicle is 5.226 m. This means that for this required \(SINRth\), decreasing \(P_{V}\) decreases the location of the relay-vehicle from the destination. It can be concluded from this figure that any transmitting vehicle should adapt the transmission power based on the required QoS.