# Quantitative Study on the Impact of Energy Consumption Based Dynamic Selfishness in MANETs +
## 6 Experimental Results
### Impact of Selfish Node Combinations  
Theoretically speaking, if the number of topology trails is large enough, the probability of having each combination is equal. However, in practical settings, mobile users move in an organized fashion, especially in the case of VANETs, which is a type of MANET. Hence, the combination of selfish nodes is a non-negligible factor to consider in the investigation of node selfishness in MANETs. Every node in MANETs has time-varying positions, speeds, and neighbors. The different selections of selfish nodes affect the network performance variously. In fact, the evaluation of various combinations of selfish nodes synthetically indicates the joint impact of mobility, speed, and positions in MANETs.  
For the purpose of the impact evaluation about the various combinations of selfish nodes, the following simulations are conducted. The evaluation metrics of the network with static and dynamic selfish nodes are investigated separately. In the simulations, five intermediate nodes are deployed with the random waypoint mobility model. In each set of simulations, there are two selfish nodes, that means 40% selfish nodes are selfish. There are 10 possible combinations, i.e., (0, 1), (0, 2), (0, 3), (0, 4), (1, 2), (1, 3), (1, 4), (2, 3), (2, 4), and (3, 4). Here, \((i,j)\) denotes that the nodes indexed \(i\) and \(j\) are selfish in this run of simulation. The two separate simulations are executed 50 times with different random seeds. The results of the simulations are depicted in Figures 9 and 10.  
Figure 9: Performance impact of different combinations of static selfish nodes (5 nodes).  
As shown in Figures 9 and 10, all three metrics in two sets of simulations fluctuate to some extent, which indicates the importance of selfish node combinations in MANETs. It reflects that even with the same proportion of selfish nodes in the network, the impact of selfish nodes is significantly different.  
In order to investigate the impact of selfish node combinations with the same node mobility, the following simulation is carried out. In the simulation, the same random seed is used for each combination of selfish nodes, which ensures the randomness is exactly the same in each simulation. The main purpose of this simulation is to investigate the differences among different selfish node combinations under the same node mobility in terms of the three evaluation metrics. The results of the simulation are illustrated in Figure 11.  
From the simulation results shown in Figure 11, we can clearly observe that the average packet loss rates of the network with static selfish nodes significantly varies with different combinations of selfish nodes. It decreases to the lowest value, 43.5484%, when \(node(1)\) and \(node(4)\) are selfish. However, it reaches the highest value, 77.8226%, when \(node(3)\) and \(node(4)\) are selfish. Even worse, the average round-trip delay of the network with static selfish nodes is affected seriously by the combinations of selfish nodes. Its highest value is 225.86 ms while the lowest value is 5.80994 ms in the simulation. The other evaluation metrics of both networks with dynamic and static selfish nodes are also influenced by the combinations of selfish nodes, although the impact is not that serious.  
The different of selfish node combinations cause significant performance decrements, which implies that some nodes play more important roles in MANETs than others because of the different positions, movement, and speeds. The performance of the network critically reduces when the key nodes are selfish in MANETs, as shown Figure 1 in Section 1.  
Figure 11: Performance impact of different combinations of selfish nodes following the same mobility model (5 nodes). Every node has the same mobility in each run, but there are different selfish node combinations.  
Figure 10: Performance impact of different combinations of dynamic selfish nodes (5 nodes).