## 4 Numerical Results and Discussion
It also reflects the role of the transmission power in deciding where the inter-vehicles should be located for communication with everything to obtain an adequate and efficient communication. Figure 6 shows the overall system data rate versus \(SINR_{th}\) for the proposed model compared with the direct communication between AV2X, assuming that \(d_{AVX}\) is 100 m and \(P_{V}\) is 23 dBm. It can be mentioned from Figure 6 that, using the adaptive proposed model, sending the information to the destination either with direct link or with cooperative communication gradually enhances the system performance. Additionally, it demonstrates how finding the best position of the relay-vehicle increases the overall system data rate. As mentioned, the adaptive proposed model increases dramatically in terms of data rate compared with the direct communication link. This figure shows how the adaptive proposed model enhances the system performance. Figure 4: Required \(SINR_{thVX}\) vs. best relay-vehicle position. Additionally, Figure 7 shows the performance of the adaptive proposed model under different conditions such as interference, \(SINR_{th}\), vehicle transmission power and \(d_{AVX}\) equal to 100 m. It can be noticed from Figure 7 that the proposed adaptive model outperforms the direct communication between AV2X in terms of overall system data rate for the two assumed \(SINR_{th}\) (0 dB and 20 dB). It also shows that increasing the required \(SINR_{th}\) increases the overall system data rate. The result obtained in Figure 7 is correlated with the one obtained in Figure 6, as it proves that the adaptive proposed model enhances the system performance by deciding based on the channel conditions whether to use direct communication or cooperative communication through finding the best relay-vehicle position for communication of the transmitting AV with the destination. Figure 5: Vehicle transmission power vs. best relay-vehicle position. Figure 6: Required \(SINR_{thVX}\) vs. overall system data rate (bps). The overall system throughput for the proposed model compared with the model presented in [12] is shown in Figure 8 at two varying vehicles' velocities, 20 km/h and 60 km/h. The proposed model clearly outperforms the performance of the model suggested in [12], as, in [12], the author utilizes the cooperative communication without taking into account the required position of the relay-vehicle. Therefore, the proposed model enriches system throughput, thanks to the assisted role of the inter-vehicle communication in addition to V2V and V2I distance optimization. Furthermore, when using the best position vehicles as a relay between _V-I_, the distance between _V-I_ gradually decreases. Accordingly, the main reason for the increment of the throughput of the proposed model is the best position of the intermediate vehicles, which promotes easy and effective route selection and transmission of V2I or from V2V. Therefore, from this result, it can be concluded that the choosing of the best position of vehicles to communicate with each other or to relay information to \(I\) plays a significant key role in increasing the efficiency of the communication between V2V and V2I. It is also noticed that the throughput of the proposed model and the model presented in [12] both decrease when increasing the number of transmitting vehicles through the road. This is mainly due to congestion in medium access and increased operation overhead at the nodes that are the vehicle-source, as well as the relay at the same time. Increasing the numbers of vehicles contributes to the increment of the number of transmitted packets, which raises the probability of packet losses and increases the length of retransmission time. The packet delivery ratio (PDR) of the proposed model is evaluated and compared with the model proposed in [12]. Figure 9 shows the ratio of the packets that successfully reach the destination for the proposed model and the model illustrated in [12], respectively, at two average vehicles' velocities of 20 km/h and 60 km/h.