# Beacon-Based Hybrid Routing Protocol for Large-Scale Unmanned Vehicle Ad Hoc Network
## 2 Beacon-Based Multi-Agent Network Hybrid Routing Algorithm
### Path Discovery and Maintenance
#### 2.2.1 Path Discovery
The PDR of the beacon-based routing protocol and the AODV and DSDV protocols varied with the number of active links in the network, as shown in Figure 6. When the beacon-based routing protocol was used in a range 5-35 communication links, the PDR was approximately 10% higher than that of AODV routing protocol. At 5-50 communication links, the PDR was approximately 20% higher than the DSDV routing protocol. The overall PDR of the beacon-based routing protocol was better than that of the two traditional routing protocols. The beacon-based routing protocol adopted the active maintenance path tree and active link mode, which was more suitable for sensing path changes in advance and \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Number of nodes & 50 \\ Bandwidths (Mbps) & 5 \\ Cover range (m\({}^{2}\)) & 1000 \(\times\) 1000 \\ Data package (Byte) & 512 \\ Active link data & 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 \\ Communication speed rate/Kbps & 10 \\ Simulation time (s) & 180 \\ communication start time/s & 80 \\ Link active time (s) & 10 \\ Node velocity (m\(\cdot\)s\({}^{-1}\)) & 5 \\ Pulse cycle (s) & 1.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Pulse cycle/sec & 1.5 \\ POR/msec & 10 \\ Pulse Propagation/msec & 70 \\ Pulse Reply/msec & 70 \\ Data Sending/sec & 1.35 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Protocol parameters. avoiding path failures and repeated path finding. Therefore, it had high reliability after networking. In Figure 6, the packet transmission rate of beacon-based routing protocol suddenly drops at node 35, mainly because the simulation startup time of six active communication links is basically the same, and the source node and destination node addresses of these six links are the same. The path query and maintenance of beacon-based routing protocol is limited to the first three stages of 140 ms.

As a result, when there are multiple data requests from the same node at the same time, the path query and maintenance cannot be completed within 140 ms. To solve this problem, we conducted the following experiment. In the experiment, the time of node access to the network was not limited and the time of node access to the network was randomly distributed within 80 s \(\sim\) 180 s (Beacon 2) and 80 s \(\sim\) 300 s (Beacon 3). The comparison between the delivery rate and the network entry time distribution of the original experiment in the 80 s + 5 s \(\sim\) 50 s (Beacon 1) is shown in Figure 7.

As shown in the figure above, the more dispersed the network time distribution of nodes is, the better the protocol delivery rate is. At the same time, there is no concurrent communication between multiple nodes at node 35, so there is no problem as shown in Figure 6.

(2) Routing Load (RL)

RL indicates the number of frames or packets borne by a communication device within a unit time. Ideally, the forwarding capability/rate should increase linearly with

Figure 6: Delivery ratios of beacon routing protocol and AODV, DSDV protocols. Figure 7: Delivery ratios of beacon routing protocol at different inbound times. the increase in load. In practice, as the load increases, the processing capability decreases. Packet congestion leads to packet loss. As a result, the forwarding rate drastically decreases. Therefore, the RL is closely related to the system stability after networking. Figure 8 showed the changes of RL of the beacon-based routing protocol and the AODV and DSDV protocols with the number of active links in the network. The result show that the cost of the RL of the beacon-based routing protocol had always been in a stable state and was unrelated to the data of the active communication link in the link, which was consistent with the original intention of the design.