## 6 Performance Evaluations
### Simulation Results
#### 6.3.3 Network Lifetime Evaluation  
In this set of experiments, the performance of the proposed algorithm is evaluated in terms of network lifetime compared to SMRP [15] and EERP [23] for the two scenarios mentioned above under different traffic rates and a different number of sink nodes.  
1. _Network lifetime evaluation under the first scenario_  
This set of experiments studies the variation of network lifetime with respect to the average traffic rate and a different number of sink nodes under environmental conditions inside the normal range.  
The first experiment evaluates the network lifetime in the first scenario. In this experiment, the average traffic rate ranges from three to 11 packets per second, using three sink nodes. Figure 12 shows the network lifetime vs. traffic rate for the first case. As seen in  
Figure 11: Influence of increasing deadline on deadline miss ratio under the second scenario.  
this figure, the proposed approach increases network lifetime compared to the others. As in this scenario, the environmental data are assumed to be in the normal range, and thus the corresponding value of the environmental impact metric is one. This improvement is because the proposed routing algorithm employs node traffic load and residual energy to balance network energy usage across sensor nodes. It prevents lost links to save energy wasted by retransmitting dropped packets. Furthermore, due to the proposed sink load metric, the proposed sink node selection algorithm effectively balances the network energy consumption among sink nodes. On the other hand, the SMRP and EERP algorithms depend on residual energy to balance energy consumption, which is inadequate according to this work's observations.  
Nevertheless, although the SMRP and EERP attempt to route data along the quickest path, their lack of knowledge regarding data transmission reliability wastes energy by retransmitting missed packets. Finally, the proposed algorithm can better use multi-sink advantages in energy balance. That is to say, the newly proposed sink load metric helps to balance the energy consumption among sink nodes  
The second experiment examines the influence of sink nodes on network lifetime in scenario 1. This experiment's network sink nodes range from one to three. Three packets per second is the normal traffic rate. Figure 13 depicts network lifetime vs. sink node number. More sink nodes enhance network lifetime, as shown in the figure. Two factors cause such results. First, adding additional sink nodes gives sensor nodes more options for routing data messages, reducing energy holes, and balancing network energy consumption. Second, additional sink nodes during network deployment reduce sensor-to-sink distance. Thus, more energy may be preserved. The proposed algorithm improves network lifetime compared to others, resulting in improved energy balance. This validates the proposed nodes' load metric and sinks load metric. SMRP and EERP do not avoid lossy links, causing packet loss. The following experiment shows that adding additional sink nodes  
Figure 12: Influence of increasing average traffic rate on network lifetime under the first scenario.  
improves network lifetime. More sinks in WSNs improve network performance but raise construction costs.