## 4 Experiments and Results  
In this section, the experiments are performed in two different environments (Terrestrial and Underwater). Later, the path loss exponent is estimated for the two environments, and a detailed analysis is presented by comparing the overall path loss in the two environments. Moreover, the influence of different water conductivities over the velocity of EM waves is presented, which is based on analytical results. To conclude, results of the possible effects of different water conductivities creating absorption losses at 2.4 GHz and other radio frequencies are presented.  
Therefore, the initial objective is to estimate the path loss exponent first in a terrestrial indoor environment, then in an underwater environment and provide a comparative analysis over the lossprofile. Estimating losses in underwater is more challenging as compared to estimating losses in a terrestrial environment. Thus, a methodology needs to be designed which could be followed to carry out the experiments. It is important that methodologies adopted should give accurate and sensible results. To put devices underwater while transmitting radio signals is an intricate task. The methodology adopted is shown in Figure 2. The path loss is a function of Signal Strength received at the receiver from a discrete distance point. In order to acquire the RSS, we have used IRIS motes from Crossbow that works over a frequency band of 2.4 GHz. The IRIS mote configuration is shown in Table 4.  
In order to estimate the RSS from the data packets, the methodology is devised in a manner that maximum samples must be taken to have a close approximation. Therefore, 4 IRIS motes (M1, M2, M3, M4) initially configured, transmit RSS data packets at 2.4 GHz from the particular distance to the Base station mote (Central mote) at the center as shown in Figure 2. The base station mote will receive those packets from the radio and will estimate RSS at that particular distance.  
Figure 2 shows the methodology to acquire RSS data that can be adopted for both environments, in the Terrestrial Indoor Environment as well as the Underwater Environment. In the experiment, four IRIS motes M1, M2, M3 and M4 are positioned at 0\({}^{\circ}\), 90\({}^{\circ}\), 180\({}^{\circ}\) and 270\({}^{\circ}\) with respect to the base station mote. All motes initially are located at one reference distance (\(d_{o}\)) with respect to base station. All four IRIS motes will transmit data packets from their locations and distinct distance points, which  
\begin{table}
\begin{tabular}{c c c} \hline
**Device** & **Parameters** & **Value** \\ \hline IRIS MOTES & Default Power (Raw Value) & 0 \\  & Default Power (dBm) & 3 \\  & Default Power (Watts) & 11.9 mW \\  & Default Channel & 11 \\  & Upper Cut-off Frequency & 2.405 GHz \\  & Lower Cut-off Frequency & 2.410 GHz \\ \hline \end{tabular}
\end{table}
Table 4: IRIS Mote Configuration.  
Figure 2: Methodology.  
will be received by the base station more. The base station more will extract the RSS from those packets and will indicate the estimated value of RSS.  
This experiment will be periodically repeated at different distance points with respect to the base station in all four directions, in order to sample the power values at discrete points to estimate the path loss exponents for both environments.