## 5 Performance Evaluation
\begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt}} \hline \hline
**Metric** & **Definition** \\ \hline Packet delivery ratio (PDR) & PDR defines the success ratio of a network. It is computed using the number of packets successfully received at the destination over the total number of data packets generated from the network nodes. \\ \hline Energy tax & Energy tax is measured in terms of power required to deliver a data packet from a source to the destination node. The unit of energy tax is joule (J). \\ \hline End-to-end delay & The delay is defined based on the total time period required by a packet to reach the destination from the source. It includes propagation, transmission, holding time, receiving and processing delays. The unit of second is used to measure the delay. \\ \hline Accumulative propagation distance (APD) & APD is the total distance required by a data packet to reach the destination successfully. It is measured in km. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Performance evaluation parameters. Figure 4: PDR of the existing and proposed protocols with varying number of nodes. The energy consumption of H2-DAB is almost 35% higher at 100 node density as compared to proposed schemes. However, it decreases gradually with the increase in node number from 150 to 300, where the difference approximately is 7%. This difference remained until node density 500. The case with Hydrocast is similar, where the gap is around 40% at 100 node number. The sudden decrease can be observed in the Figure 5. This ends with the gap of 9% from proposed techniques and almost 3% of difference from H2-DAB. Figure 6 shows that the end-to-end delay of all the three protocols first increases with increase in the number of nodes but then decreases. When the network is too sparse, most of the packets are delivered from low depth nodes. The end-to-end delay increases with increasing number of nodes because the probability of void hole decreases and the probability of path establishment increases from the high depth nodes, which increases the end-to-end delay per packet. When number of nodes exceed 200, end-to-end delay decreases due to more PFNs in a dense network which reduces the number of hops between source and sink. WDFAD-DBR has high end-to-end delay due to packet holding time. In contrast, Re-Intar and Intar do not consider holding of the packet. Thus, end-to-end delay is reduced only to propagation delay, transmitting delay and receiving delay. In Intar, high end-to-end delay is due to long propagation path because of avoiding channel interference. Re-Intar reduces propagation distance of the packet by using depth of PFN. However, Intar shows better performance than Re-Intar when node number is 100 in network because Re-Intar also uses backward transmission. Relatively, Re-Intar is approximately 37.16% more efficient than WDFAD-DBR and 10.21% more efficient than Intar in end-to-end delay. It can be observed that delay in both Hydrocast and H2-DAB is higher than the proposed schemes. Hydrocast has more delay as we have mentioned in the discussion of PDR that it prefers backward transmissions to handle void hole problem. In this process, it has to traverse more hops which increase delay and also dissipate more energy as well. H2-DAB has more delay, but, at the end, it outperforms  
Figure 5: Energy tax of the existing and proposed protocols with varying number of nodes. both WDFAD-DBR and Hydrocast. This scheme uses unique identifiers which reduce the path length with the increase in node density. Similar to end-to-end delay, APD of all the three protocols first increases with increase in the number of nodes and then decreases, as shown in Figure 7. When the network is too sparse, most of the packets are delivered from low depth nodes. When the number of node increases, high depth nodes communicate with sink which increases APD per delivered packet.