## 5 Protocol Performance Evaluation
### Simulation Setup Description  
The network used in the simulation scenario adopted is illustrated in Figure 3. It consists of 100 stationary sensors and a base station. More precisely, the nodes are supposed to be randomly deployed within the WSN field which is a square area of side \(L=100\) m. The base station is located at a distance \(D\) away from the closest point of this area. At each one of the simulation tests, \(D\) takes one value among 100, 200 or 300 m. The nodes transmit sensed data during their corresponding time slots, only when an incident is detected. This happens whenever the current value of the sensed attribute is greater than the hard threshold which is set to 100 and the current value of the sensed attribute differs from the sensed value by an amount equal to or greater than the soft threshold, which is set to 2. During simulation, incidents are generated at random locations within the network field, each of them concerning a region of arbitrary area. Figure 3: Graphical depiction of the architecture of the WSN scheme adopted. The radio model that is used is the same adopted in [9]. By using this approach, an energy loss of \(d^{2}\) due to channel transmission is assumed. The energy \(E_{Tx}\)_(k,d)_ that a node dissipates for the radio transmission of a message of \(k\) bits over a distance \(d\) is due to running both the transmitter circuitry [\(E_{Tx-elec}\)_(k)] and the transmitter amplifier [\(E_{Tx-amp}\)_(k,d)] and is given by:  
\[ \begin{split} E_{Tx}(k,d)&=E_{Tx-elec}(k)+E_{Tx- amp}(k,d)\Rightarrow\\ E_{Tx}(k,d)&=E_{elec}\cdot k+\varepsilon_{amp} \cdot k\cdot d^{2}\end{split}  \tag{3}\]  
where \(E_{elec}\) is the transmitter circuitry dissipation per bit, which is supposed to be equal to the corresponding receiver circuitry dissipation per bit and \(\varepsilon_{amp}\) is the transmit amplifier dissipation per bit per square meter. Similarly, the energy \(E_{Rx}\)_(k)_ dissipated by a node for the reception of a _k_-bit message is due to running the receiver circuitry [\(E_{Rx-elec}\)_(k)] and is given by:  
\[E_{Rx}(k)=E_{Rx-elec}(k)\Rightarrow E_{Rx}(k)=E_{elec}\cdot k \tag{4}\]  
Moreover, a node dissipates additional sums of energy while being in idle state (equal to \(E_{elec}\)) and while sensing (equal to 0.1\(\cdot E_{elec}\)). The initial node energy \(Er_{i}(0)\) was set to 0.5 J for the half of the simulation tests performed. For the rest half of the simulation tests \(Er_{i}(0)\) was supposed to take random values in the range between 0.1 J and 0.5 J. It is assumed that each node has the ability of monitoring its residual energy. It is further assumed that the radio channel is symmetrical. Hence, the energy required to transmit a message from a source node to a destination node is equal to the energy required to transmit the same message from the destination node back to the source node for a given SNR. Finally, it is assumed that the communication environment is both contention and error free. Thus there is no need for retransmission. The parameters adopted during simulation tests along with their respective values are summarized in Table 1.  
Finally, IEEE 802.11 b is the wireless communication standard used in the simulation tests performed. Generally, the selection of this standard enables the high rate transmission over long distances. Alternatively to this, IEEE 802.15.4 can be used in many applications. The great advantage \begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter** & **Value** \\ \hline Network size & 100 m \(\times\) 100 m \\ Number of sensors & 100 \\ Distance from WSN field to the base station (\(D\)) & 100 / 200/ 300 m \\ Node initial energy [\(Er_{i}(0)\)] & 0.5 J / 0.1–0.5 J \\ Transmitter circuitry dissipation (\(E_{elec}\)) & 50 nJ/bit \\ Amplifier dissipation (\(\varepsilon_{amp}\)) & 100 pJ/bit/m\({}^{2}\) \\ Data packet size & 100 bits \\ Soft Threshold & 2 \\ Hard Threshold & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation Parameters.