# An Improved Energy-Efficient Routing Protocol for Wireless Sensor Networks
## 4 Simulation Results  
In this section, to evaluate the performance of the proposed IEE-LEACH protocol in the WSN, the existing LEACH, LEACH-Centralized (LEACH-C) [18], LEACH-M [22], O-LEACH [23], energy-efficient LEACH (EE-LEACH) [36], Stable Energy Efficient Network (SEEN) [24], and LEACH-eXtended Message-Passing (LEACH-XMP) [25]protocols are used in comparison in the simulation experiments. Simulation experiments were carried out using MATLAB 2014a (MathWorks, Natick, MA, USA). A wireless sensor network system model consisting of 100 homogeneous SNs [37] randomly distributed in 100 m \(\times\) 100 m square area with different initial energies is considered. The BS is placed at the coordinate (50, 100). Therefore, the maximum distance between the SN and the BS is \(50\sqrt{5}\)m (approximately 111.8 m). We run the simulation for 3500 rounds, and the value of the time interval between rounds is 20 s [4]. Table 1 shows the parameter configurations in the WSN that are employed in the simulation.  
The performance metrics of the WSN that are used to evaluate the performance of the algorithm as follows [38; 39]:  
* Stability Period: The time span from the beginning of network operation until the first dead sensor occurs, which can be calculated by \[T_{stability}=t_{FND}-t_{start},\] (24) where \(t_{FND}=20\times FND\), \(FND\) is the number of rounds after which the first sensor died, \(t_{FND}\) is the time that the first dead sensor occurred, and \(t_{start}\) is the time of the beginning of network operation.  
\begin{table}
\begin{tabular}{c c} \hline
**Parameters** & **Values** \\ \hline \(E_{dec}\) & 50 nJ/bit \\ \(E_{DA}\) & 5 nJ/bit/signal \\ Transmitter Amplifier (\(\epsilon_{\text{fs}}\)) if \(d\leq d_{0}\) & 10 pJ/bit/m\({}^{2}\) \\ Transmitter Amplifier (\(\epsilon_{\text{mp}}\)) if \(d\geq d_{0}\) & 0.0013 pJ/bit/m\({}^{4}\) \\ \(p\) & 0.05 \\ \(d_{0}\) & 87 m \\ Data Packet Size & 4000 bits \\ Data Packet rate & 1 packet/s \\ \hline \end{tabular}
\end{table}
Table 1: Simulation parameters.  
* Network Lifetime: The time span from the beginning of network operation until the last live SN dies, which can be calculated by \[T_{lifetime}=t_{LDN}-t_{start},\] (25) where \(t_{LND}=20\times LND\),\(LND\) is the number of rounds after which all sensor nodes died, and \(t_{LND}\) is the time at which all sensor nodes died.
* The Amount of Transmitted Data: The total quantity of data sent from the nodes (including the CHs and other nodes) in the WSN to the BS can be calculated by \[data=data_{CHt0 BS}+data_{NtoBS},\] (26) where \(data_{CHt0 BS}\) is the amount of transmitted data by the CHs to the BS, and \(data_{NtoBS}\) is the amount of transmitted data by nodes to BS. In particular, in this paper, \(data_{NtoBS}\) concerns nodes near the station of the base, and which does not contribute to the formation of clusters.
* Energy Consumption of Network: The energy consumption of wireless sensor networks mainly includes circuit energy consumption and power amplifier energy consumption, and the latter is dominant. The energy consumption of each round in the network can be calculated by Equation (11) or Equation (15) in different channel models.
* Number of CHs per Round: The number of nodes that send information aggregated from their cluster members directly to the BS is elected according to the threshold condition \(T(s_{i})\). This can be calculated by Equation (12) or Equation (16) in different channel models.  
In terms of the reliability and lifetime of the WSN, the stability period of the WSN is of great value to research because the network is mainly responsible for data transmission. Furthermore, more attention is paid to the lifetime of the WSN, the number of data transmissions (to the BS), and the residual node energy, which objectively reflects the network lifetime situation.