# Integrated Evaluation of Reliability and Power Consumption of Wireless Sensor Networks
## 6 Experimental Evaluation
### Sensitivity Analysis  
Activity _Do Sensitivity Analysis_ (see Figure 3) is responsible for creating and evaluating multiple WSN configurations according to the parameters (called factors) and values (called levels) defined by users. This activity is an essential one for identifying the influence of each factor on power consumption and reliability of WSN. To perform the sensitivity analysis, we considered the factors and levels shown in Table 2. We chose these factors because they are widely known in WSN domain. About the levels, they will be explained in the next paragraphs. We defined that the first level (\(-1\)) is the worst case and second one (\(+1\)) is the best based on the results of the WSN power consumption [16; 18; 21; 22; 23]. Positive numeric levels are five times higher than the next level of the same factor, e.g., 0.001 Joules and 0.005 Joules. In this way, we avoid favouring a particular factor to influence more or less the power consumption and/or reliability of the WSN. The values assigned to _Initial Energy Level_ (0.001 and 0.005) and _Node Number_ (20 and 100) were defined based on ones adopted in [16; 18; 21]. Furthermore, it is worth observing that there is a relationship between the factors _Sending Regular Rate_ and _Packet Size_. If a sensor node sends a 50 kb packet (first level of the Packet Size) every 2 s (first level of _Sending Regular Rate_), the same amount of data can be sent over the same period of time if it sends 250 kb every 10 s (second level of the _Packet Size_ and _Sending Regular Rate_, respectively). The goal is to check if it is more advantageous to frequently send small packets or send a large packet in a longer period. Additionally, all sensor nodes send the packet to the sink node and the periodicity in seconds helps to accelerate the evaluation process because it only finishes when all sensor nodes die, i.e., the energy level is 0 Joules. Another relationship is between the _Place Size_ and _Initial Radio Range_. It is important to note that the sink node is located in the centre of the WSN. For example, if the _Place Size_ is 500 m \(\times\) 500 m, the sink node is in the location (250,250). To ensure that any sensor node has direct communication with the sink node, it is necessary that all sensor nodes have an _Initial Radio Range_ of the (at least) 250 m, which is the first level of this factor. The routing protocols called GOSSIPING and DIRECT were chosen because they are the worst and the best power consumption according to [16; 21], respectively. In fact, the protocol FLOODING had the worst performance in the two mentioned papers. However, it was not used because the network did not spend much time active, making it impossible to evaluate the impact on the WSN reliability. Finally, the levels of _Placement Algorithm_ are based on the Deployment Strategy-Oriented Lifetime [22; 23]. The WSN can contain two regions (see Figure 18), one near and another far from the sink node, which is located in the centre of the WSN as mentioned before. The WSN power consumption will be different because sensor nodes need more energy to transmit a packet when they \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Factor** & **Acronym** & **Level (\(-1\))** & **Level (\(+1\))** \\ \hline Energy Level & IEL & 0.001 Joules & 0.005 Joules \\ Packet Size & PaS & 250 kb & 50 kb \\ Routing Protocol & RP & GOSSIPING & DIRECT \\ Initial Radio Range & IRR & 1770 m & 354 m \\ Placement Algorithm & PA & Far & Closed \\ Node Number & NN & 20 & 100 \\ Sending Regular Rate & SRR & 2 s & 10 s \\ Place Size & PIS & 500 m \(\times\) 500 m & 100 m \(\times\) 100 m \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Factors and Levels. are far from the sink node. Besides that, the WSN reliability may vary according to the distance from the sensor node to the sink node, because WSN reliability is affected by the WSN power consumption as shown by the third experiment in Section 6.2. It is worth observing that the factors _Routing Protocols_ and _Placement Algorithm_ are closely related.