# Quantitative Study on the Impact of Energy Consumption Based Dynamic Selfishness in MANETs +
## 6 Experimental Results
### Impact of Selfish Node Proportions  
Selfish nodes play negative roles in MANETs as the intermediate nodes that refuse to forward packets for others' interests. The multi-hop communication is required in MANETs whenever a node sends a packet to the destination out of its transmission range of the node. It points out that cooperation among nodes in MANETs is indispensable in most cases. In order to make clear how the proportions of selfish nodes, including static and dynamic ones, affect the network performance in MANETs, the following simulations are conducted. The three evaluation metrics are investigated in the MANET with 50 intermediate nodes. In the simulations, the selfish node proportion varies from 10% to 90% with the increment of 10%. The proportions of 0% and 100% selfish nodes are excluded in the simulations for the following reasons. In the case of 0% selfish nodes, all nodes in the network altruistically cooperate with each other, which was discussed earlier in this section. In the case of 100% of selfish nodes, all nodes in the network are selfish. Especially in the network with static selfish nodes, no packet sent by the sender will reach the receiver because the receiver is out of the transmission range of the sender in our simulation setting, and there is no intermediate node to forward packets because they are static selfish. The simulation results are shown in Figure 8.  
The average packet loss rate of the network increases with increasing proportions of selfish nodes in both dynamic and static selfish networks (Figure 7(a)). A large proportion of selfish nodes leads to a high packet loss rate in the MANET. The average packet loss rate of the network with static selfish nodes increases drastically. This significant performance reduction is caused by the fact that the absolute number of selfish nodes increases with the increasing proportion of selfish nodes in the network, which finally leads to very few intermediate nodes in the network to assist in routing and forwarding tasks. However, that of the network with dynamic selfish nodes, by contrast, does not increase obviously. The reason is that even though the proportion of dynamic selfish nodes is high, it does not mean the absolute number of selfish nodes is large. In the network with dynamic selfish nodes, the node selfishness is only determined by the dynamic residual energy level. The nodes with higher residual energy levels always act altruistically, and vice versa. In Figure 7(c), the average throughput of both networks with static and dynamic selfish nodes is depicted. The average throughput of the network with dynamic selfish nodes  
Figure 8: Performance impact of various proportions of selfish nodes (50 nodes). does not decrease too much, whereas that of the network with static selfish nodes reduces drastically. The main reason of this occurrence is the average packet loss rate. The average round-trip delay of both networks with static and dynamic selfish nodes is depicted in Figure 8b. In the network with dynamic selfish nodes, the average round-trip delay is more stable than that in the network with static selfish nodes. In the network with static selfish nodes, as the proportion of static selfish nodes increases, the average round-trip delay becomes longer for each packet successfully received by the destination; it is more and more difficult to discover a valid route from the sender to the receiver when more and more static selfish nodes are involved in the network. However, the average round-trip delay becomes shorter when the proportion of selfish nodes is extremely high, for example 90%. From another point of view, it reflects that the number of utilizable nodes for data transmission is very small. It further results in low probabilities to establish valid routes with a small number of cooperative nodes having a high random mobility. Even if the route is established, the hop count of the route is small and the round-trip delay is short. In this simulation, the selection of selfish nodes is predetermined manually.