# 3D Void Handling Geographic P2P-RPL for Indoor Multi-Hop IR-UWB Networks
## 4 Performance Evaluation
### Greedy Forwarding and Void Handling Point-to-Point RPL in 3D Indoor Environments
#### 4.2.1 125 Node Grid Deployment in 75 m \(\times\) 75 m \(\times\) 75 m Network Configuration  
Figure 14 depicts the network node deployment of 125 nodes. Nodes are located in a grid pattern with (\(\pm\)5 m, \(\pm\)5 m, \(\pm\)5 m) of randomness. Figure 15 shows the result of the route discovery success ratio. P2P-RPL, PF-P2P-RPL, ER-RPL, GVA-P2P-RPL, and greedy forwarding have about 99.7%, 99.3%, 99.5%, 99.3%, and 91.9% of the route discovery success ratio, respectively. Since the local minima led to routing failures, the greedy forwarding case achieved a 7.4% lower route discovery success ratio than GVA-P2P-RPL. This result shows that the recovery mode of GVA-P2P-RPL locally broadcasts P2P-DIO messages when void nodes are encountered. The proposed GVA-P2P-RPL protocol is as reliable as P2P-RPL in route discovery for 3D environments where local minimum problems are observed more often than for 2D. Figure 16 shows the results of the number of P2P-DIO messages sent and number of P2P-DIO messages received. As shown, the routing overhead result of GVA-P2P-RPL outperforms that of P2P-RPL, PF-P2P-RPL and ER-RPL. GVA-P2P-RPL reduces about 94.5%, 87.1% and 92.4% of the number of DIOs sent, compared to P2P-RPL, PF-P2P-RPL and ER-RPL, respectively, and about 98.9%, 97.7% and 98.7% of the number of DIOs received, compared to P2P-RPL, PF-P2P-RPL and ER-RPL, respectively. Figure 17 shows the result of energy consumption and hop count. In the same sense as the overall routing overheads of GVA-P2P-RPL being reduced compared to those of P2P-RPL, PF-P2P-RPL and ER-RPL, the energy consumption results of GVA-P2P-RPL are also significantly reduced. GVA-P2P-RPL reduces about 97.5%, 94.6% and 96.8% of the energy consumption compared to P2P-RPL, PF-P2P-RPL and ER-RPL, respectively. The average hop count of GVA-P2P-RPL is about 0.198 hops longer than that of P2P-RPL, about 0.216 hops longer than that of PF-P2P-RPL and about 0.207 hops longer than that of ER-RPL. GVA-P2P-RPL greedily selects the closest neighbor node to the destination whenever greedy forwarding is possible, and it is possible that other neighbor nodes that may construct shorter routes are not selected. Such cases occur when P2P route discovery  
Figure 14: 75 m \(\times\) 75 m \(\times\) 75 m 125 nodes grid deployment. encounters the local minimum. As a result, GVA-P2P-RPL leads to a slightly higher hop count value of the discovered route than P2P-RPL, PF-P2P-RPL and ER-RPL. Figure 18 shows the result of the route discovery time. The average route discovery time of GVA-P2P-RPL with the adaptive trickle timer (ATT) is about 39.9% less than that of P2P-RPL, about 41.0% less than that of PF-P2P-RPL, about 40.5% less than that of ER-RPL, and about 54.8% less than that of GVA-P2P-RPL with the standard trickle algorithm. As the trickle algorithm is used in the routing simulations unlike the previous end-to-end network delay measurement experiment, the route discovery time results are in the range of 100 to 250 ms, which is much longer than the average network delay result of 259.3 us. With the standard trickle algorithm, P2P-RPL, PF-P2P-RPL and ER-RPL outperform GVA-P2P-RPL. Figure 16: Number of DIOs sent and number of DIOs received. Figure 17: Energy consumption (mJ) and hop count. Figure 15: Route discovery success ratio. That is, more nodes participating in route discovery procedure leads to a higher probability of scheduling an earlier P2P-DIO message transmission time in P2P-RPL, PF-P2P-RPL and ER-RPL. ATT uses 25 ms as its \(I_{init}\) parameter value, while the standard trickle algorithm uses 26 ms. ATT also gives higher transmission priority to nodes closer to the destination by setting these nodes' listen-only periods to be shorter. As explained in the previous section, these two parameter value changes are reasonable since GVA-P2P-RPL has far fewer nodes participating in the route discovery procedure and fewer contentions among the one-hop neighbor nodes. As a result, the shorter route discovery time is achieved compared to P2P-RPL, PF-P2P-RPL and ER-RPL.