# Optimization of the AODV-Based Packet Forwarding Mechanism for BLE Mesh Networks
## 4 Optimized-AODV Protocol Topologies and Testbed Design
### Experimental Results: O-AODV Linear Topology with 10 Nodes  
These studies were carried out using the linear topology of ten nodes. There are nine sources transmitting simultaneously towards the sink. Hence, the links closer to the sink carried the packets generated by previous nodes from the previous hops, resulting in the link closest to the sink being the bottleneck link with the highest amount of traffic.  
This section summarizes the experimental findings in terms of the end-to-end delays, average per-hop delays, route request to route reply setup time, overhead, and PDR.  
According to the results shown in Figure 8, the end-to-end delay increased linearly as the number of hops increased, and O-AODV was proven efficient in comparison with the other two protocols.  
According to the results shown in Figure 9, the average per-hop delay for all three protocols was almost linear, with better O-AODV results than the other two protocols. We achieved an average per-hop delay of 840 ms compared to 1100 ms for AODV and 1000 ms for mesh (flooding) protocols.  
As shown in the graph depicted in Figure 10, mesh (flooding) had a very high overhead of more than 80% compared to the O-AODV and AODV protocols. Furthermore, O-AODV incurred a much lower overhead by reducing message retransmissions and TTL values.  
\begin{table}
\begin{tabular}{c c c c} \hline
**Experiment Parameters** & **Scenario 1** & **Scenario 2** & **Scenario 3** \\ \hline No of Experiments & 7 & 7 & 7 \\ \hline Topology & Linear Topology with 10 Nodes & Multipath Topology with 6 Nodes & Multipath Topology with 10 Nodes \\ \hline Link Speed & 2 Mbps & 2 Mbps & 2 Mbps \\ \hline Offered Data Rate & 10 PDUs per Second & 10 PDUs per Second & 10 PDUs per Second \\ \hline Packet Size & 15 Byte & 15 Byte & 15 Byte \\ \hline No. of Packets Transmitted from the Source & 100 & 100 & 100 \\ \hline Number of Sources and Snks & 9 Sources, 1 Sink & 1 Source, 1 Sink & 1 Source, 1 Sink \\ \hline Transmission Power & \(-\)40 dBm & \(-\)40 dBm & \(-\)40 dBm \\ \hline Transmission Range & Approximately: 2-2.5 m & Approximately: 2-2.5 m & Approximately: 2-2.5 m \\ \hline Relay Configuration & Enabled & Enabled & Enabled \\ \hline \multirow{3}{*}{Provisioning} & Enabled but Given Hardcoded & Enabled but Given Hardcoded & Enabled but Given Hardcoded \\  & Network, Application, & Network, Application, & Network, Application, \\  & and Device Keys & and Device Keys & and Device Keys \\ \hline \multirow{2}{*}{Packet Duplication Factor} & 3 Transmissions & 3 Transmissions & 3 Transmissions \\  & with a 20 ms interval & with a 20 ms interval & with a 20 ms interval \\ \hline \end{tabular}
\end{table}
Table 2: Common experiment setup and configurations.  
Figure 8: End-to-end, one-way delay: O-AODV, AODV, and mesh (flooding) comparison.  
As illustrated in Figure 11, both O-AODV and AODV showed a slight linear increase in the route request to route reply to setup time with an increase in the number of hops, with the O-AODV protocol taking approximately 16% less time.  
In Figure 12, O-AODV outperformed AODV in terms of the packet delivery ratio with 85% compared to 70%, but it was lower than the PDR for Mesh (Flooding), which was 95%.  
Figure 11: RREQ-RREP setup time: O-AODV and AODV comparison.  
Figure 10: Overhead: O-AODV, AODV, and mesh (flooding) comparison.  
Figure 9: Average per-hop delay: O-AODV, AODV, and mesh (flooding) comparison.