# Comparative Study of Energy Efficient Routing Techniques in Wireless Sensor Networks
## 4 Simulation Results
### Simulation Results and Performance Evaluation  
In the following, the protocols are compared in terms of network lifetime, stability/instability periods and energy consumption. \begin{table}
\begin{tabular}{c c} \hline \hline
**Network Parameters** & **Values** \\ \hline Sensing area & 100 m \(\times\) 100 m \\ \hline Nbr of sensors & 100 \\ \hline Location of the sink & 50, 50 \\ \hline Packet size & 4000 bits \\ \hline Sensor energy & 0.5 J \\ \hline Energy consumption on the circuit (E\({}_{elec}\)) & 50 nJ/ bit \\ \hline Dissipation energy (Efs) & 10 pJ/ bit/ m\({}^{2}\) \\ \hline Transmission energy (ETx) & 50 nJ \\ \hline Reception energy (ERx) & 50 nJ \\ \hline Data aggregation & 5 nJ/ bit/ report \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Model parameters. * **Network lifetime** The network lifetime can be defined as the duration between the start of the simulation and the death of the last node of the network. The main objective of routing protocols is to extend the network lifespan to the maximum while keeping the QoS. The evolution of the network lifespan of the compared protocols is shown in Figure 4.  
The random CHs selection mechanism adopted by LEACH and Mod-LEACH protocols is the reason for the limited network lifetime. In fact, several nodes can simultaneously take the role of a CH without any need. This affects the energy of the sensors and then creates several isolated areas. Contrariwise, ILEACH and M-GEAR ensure a longer network lifetime. This is explained, respectively by the positive effect of the energy management function and the use of data aggregation tree-based on a multi-hop model in the case of iLEACH and due to the direct communication mechanism in the non-clustered regions and the use of a rechargeable gateway in the case of M-GEAR. The network lifetime is more important with E-DEEC and multichain-PEGASISIn fact, the existence of several types of nodes in the case of E-DEEC improves the energy efficiency of the WSN and guarantees better coverage while the Sink mobility ensured by multichain-PEGASIS protocol causes good load balancing and offers a long lifetime. * **Stability/instability periods** The network lifespan is made up of the two adjoining parts. The first part, starting from the beginning of the network until the death of the first node, is called the period of the stability, contrary to the instability period, which starts from the death of the first node until the last one in the network. Figure 5 shows these two periods for the compared protocols. Multichain-PEGASIS presents the best stability period with more than 1650 rounds. This is explained by the energy gain caused by the sink mobility, while the best period of instability is achieved by E-DEEC protocol thanks to the high energy levels of some sensors. * **Remaining energy** The remaining energy, shown in Figure 6, presents the total energy remaining in the battery of the sensors at round R.  
Data routing is the most energy-consuming task in WSNs. Hence, the routing protocol must take maximum advantage of intelligent techniques to reduce energy consumption. Figure 6 shows that E-DEEC and multichain-PEGASIS manage the energy of the network in an optimized way due to the techniques used by these protocols like mobility, direct communication, and the use of various energy levels, which significantly improve the energy conservation in WSNs. Figure 4: Network lifetimes. The energy variance (EV), shown in Figure 7, reflects the difference of residual energy of each node in the network, which can be affected by several parameters such as distribution, sensor location and activity rate. The shape and the volatility of the EV curves give us more precise and readable information about the load balancing in the network. In fact, the smaller the value and the smaller the curve fluctuation, the more balanced the energy of the network. Hence, the multi-chain PEGASIS protocol presents the best results explained by the positive effect of sink mobility. Figure 5: Stability and instability periods.