# Weight-Based PA-GPSR Protocol Improvement Method in VANET
## 5 Simulation and Performance Analysis
### Result Analysis
#### 5.2.1 Packet Loss Rate  
Figure 9 shows the packet loss rate of each routing protocol when changing the number of nodes and CBR connections. As the number of nodes increases, the number of reliable links and network connectivity increase, thereby increasing the probability of data packets successfully reaching the destination node. On the whole, when the number of nodes increases, the packet loss rate of all protocols will decrease. Considering the distance, direction of movement, reliable node density, and cumulative communication duration required to select the next hop node, the probability of W-PAGPSR successfully sending data packets is higher. In a network environment with several nodes from 30 to 110, data packets are more likely to be discarded in the process of finding the correct path. As the number of nodes increases, the number of neighbor nodes available for decision-making increases; thus, the packet loss rate of W-PAGPSR is lower than those of other protocols. In addition, each data packet has a lifetime to stay in the network, which reduces the probability of routing loops occurring in sparse networks, thereby reducing the packet loss rate. As shown in Figure 9a, with five CBR connections, the packet loss rate of all nodes of W-PAGPSR is lower than those of GPSR, MM-GPSR, and PA-GPSR, respectively. As shown in Figure 9a, with five CBR connections, the packet loss rate of all nodes of W-PAGPSR is lower than those of MM-GPSR, PA-GPSR, and GPSR, respectively. As shown in Figure 9a, the average packet loss rate of W-PAGPSR is 24.68%, 24.41%, and 17.48% lower than those of GPSR, MM-GPSR, and PA-GPSR, respectively. Neither GPSR nor MM-GPSR considers the link quality in the process of selecting the next hop; thus, the packet loss rate is higher. MM-GPSR selects the next hop by accumulating the communication time. This choice is not the nearest hop to the destination, which leads to an increase in the number of hops and increases the probability of packet loss by the node. From Figure 9b, it can be seen that the packet loss rate of the four protocols at 70 nodes has increased. As shown in Figure 9b, the average packet loss rate of W-PAGPSR is 25.09%, 25.08%, and 15.87% lower than those of GPSR, MM-GPSR, and PA-GPSR, respectively. This result occurs because when the number of CBR connection pairs increases, the network load increases and a large number of nodes access similar links, increasing the chance of collision and interference between data packets, thus increasing the packet loss rate. When the number of nodes reaches 110, W-PAGPSR performance tends to stabilize because it balances the load between nodes in the network, which helps to make more efficient use of available bandwidth and, ultimately, deliver more data packets. As shown in Figure 9c, the average packet loss rate of W-PAGPSR is 22.98%, 244.08%, and 10.77% lower than those of GPSR, MM-GPSR, and PA-GPSR, respectively. As shown in Figure 9d, the average packet loss rate of W-PAGPSR is 25.14%, 26.53%, and 12.38% lower than those of GPSR, MM-GPSR, and PA-GPSR, respectively. Overall, the packet loss rate of W-PAGPSR in sparse scenarios is smaller than those of GPSR, MM-GPSR, and PA-GPSR. This result occurs because W-PAGPSR chooses the next hop with a more stable connection, a smaller distance to the destination, and better connectivity. As shown in Figure 9, judging from the overall trend, from 30 to 70 nodes, the packet loss rate advantage of W-PAGPSR is not obvious. This result occurs because the number of nodes is insufficient, and the improvement strategy of W-PAGPSR cannot take advantage of the advantages of multi-parameter selection of relay nodes. From 70 to 90 nodes, the packet loss rate of W-PAGPSR has obvious advantages. This result occurs because a sufficient number of nodes can use improved greedy forwarding and perimeter forwarding methods for routing decisions, thereby reducing the packet loss rate. From 90 to 110 nodes, the decline in packet loss rate slows down.