## 3 Performance Evaluation Results and Discussion
### Effects of a on the FLRAF  
An excessively large or overly small forwarding area can lead to corresponding problems. For example, when the forwarding area is too small, it may be difficult to locate a suitable next-hop node, potentially resulting in routing voids and data transmission interruptions. Conversely, when the forwarding area is too large, the overall energy consumption of the network tends to increase. Therefore, simulation experiments were conducted to determine the optimal forwarding area. As shown in Figure 3, we agreed that the angle \(\gamma\) is the half vertex angle of the \"cone\" forwarding area, and \(\alpha=\frac{\gamma}{90^{\circ}}\), that is, \(\alpha=0\) corresponds to \(\gamma=0^{\circ}\) and \(\alpha=1\) corresponds to \(\gamma=90^{\circ}\). The subsequent simulation phase focuses on examining how variations in \(\alpha\) affect the performance of the FLRAF protocol. We varied \(\alpha\) from 0.1 to 1 in order to identify the optimal value and to compare the performance of the FLRAF protocol with other existing protocols under these conditions. To complete this simulation work, we will set the simulation parameters as shown in Table 5.  
Figure 12 shows the impact of \(\alpha\) on the delivery rate of data packets. First, the figure shows that as \(\alpha\) increases, the forwarding area expands, leading to a rise in the number of nodes within this area. Consequently, the probability of routing voids or transmission interruptions decreases accordingly. As a result, the number of received data packets will increase. After \(\alpha>0.7\), the delivery rate begins to stabilize and slightly decline. This is because the forwarding area becomes sufficiently large, and there are already enough nodes available to participate in the forwarding process. Thanks to the fuzzy reasoning process, we choose nodes with better states to act as forwarding nodes. However, even if we further increase the forwarding area and add more nodes, the members located near the forwarding node of the previous hop are not suitable to form a candidate set. Therefore, they have a minimal positive impact on the final packet delivery rate. On the contrary, theincreased node density may lead to more data collisions, which can negatively affect the packet delivery rate. Figure 13 illustrates the impact of \(\alpha\) on the average end-to-end delay. When \(\alpha<0.3\), the forwarding area is still at a relatively small level, and the number of candidate nodes contained in the forwarding area is also limited. At this time, the routing path may be longer, or the next-hop candidate node may not be found, resulting in increased delay caused by transmission interruptions. As \(\alpha\) increases, on the one hand, the number of candidate nodes available for the previous-hop node increases; on the other hand, more nodes with longer \(AD\) appear in the candidate area. Therefore, the delay will be significantly reduced. Finally, due to the mobility of the nodes, there is a slight change in their relative position, and similar to the reason resulting in the trend of \(PDR\) in Figure 12, there is a slight increase in latency caused by data collisions. Figure 12: Effects of \(\alpha\) on packet delivery rate. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Routing protocol & FLRAF \\ MAC layer protocol & Broadcast MAC \\ Propagation model & Underwater Propagation \\ Channel & Underwater Channel \\ Number of nodes & 400 \\ Node transmission range & 100 m \\ Simulation time & 500 s \\ Size of simulation scene & 800 m \(\times\) 800 m \(\times\) 800 m \\ Moving model & RandomWalkMobilityModel \\ Maximum moving speed of node & 4 m/s \\ Application layer data rate & 3 kbps \\ Node transmit, receive and idle power & 2.0 W, 0.75 W, 0.008 W \\ \(\alpha\) in FLRAF & 0.1–1 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Simulation parameters for optimal forwarding area verification. Figure 14 shows the impact of \(\alpha\) on the average energy consumption of the network.