## 3 Statistical Analysis of the Collected Data for Different Seasons  
### Winter and Spring Season  
In this section, the performance of the FSO link, during winter season (i.e., December, January, and February) and spring season (March) in terms of PDR variations is presented.  
The UDP application measuring the PDR is running continuously 24 h per day. Every day data is collected from the system. For each month, the data is collected for a window of 30 min in each hour  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Serial No.** & **Sensors** & **Parameter Measured** & **Uncertainty/Non-Linearity of the Measured Parameter** \\ \hline
1 & LM 35 & Ambient Temperature & \(\pm\frac{1}{2}\)\(\circ\)C \\
2 & HHH-4000 & Relative Humidity & \(\pm\)3.5\(\%\)\(RH\) \\
3 & SP 110 & Solar Irradiance & \(<\)1\(\%\) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Details of the sensors for collecting environmental parameters.  
Figure 2: Diagram to show how the data, collected from two systems, are used in analysis. PDR: Packet Delivery Ratio; FPGA: Field Programmable Gate Array.  
of the day. The values of each hour of the day of the month are averaged. Thus, for each month the average collected data as a function of time and weather factors are presented.  
In Figure 3, the behavior of FSO link during December 2014, January 2015 and February 2015 is presented. The plots contain the PDR, temperature, humidity and solar irradiance as a function of time. As shown in Figure 3, the weather in Qatar during December is considered moderate, where the temperature varies between 14 \({}^{\circ}\)C and 28 \({}^{\circ}\)C and the humidity is between 38% and 90%. The FSO performs well as the PDR reaches a high level and oscillates between 95% and 100%. It should also be noted that the humidity and temperature fluctuates even at night and can affect the behavior of FSO link. Similar performances can be seen in January and February, which is considered winter season in Qatar as the temperature, is the minimum during this time. The temperature is however very high if compared to Europe and America during same season.  
In Qatar, March is considered as spring season. In Figure 4, the PDR variations along with temperature and humidity during March is presented. As shown from the plots, the FSO has the same performance as the previous months. In fact, the FSO shows a better performance and the PDR does not fall below 95%.  
From the figures, it can concluded that during winter and spring seasons, the PDR varies slowly during a single day and it can be considered to be constant with a good performance. On the other hand, as discussed before, the temperature also varies slowly and does not reach high level. Thus it validates that there is relationship between the low variation of weather factors and the good performance of the FSO link. In Qatar, the temperature and the humidity during the winter and the spring seasons are low and does not cause much effect on the PDR. To further investigate and validate the relation of the FSO link performance with weather factors, in the next section, the measurement of pre-summer  
Figure 3: Behavior of FSO link vs weather factors during (**a**) December 2014, (**b**) January 2015 and (**c**) February 2015 (winter season).  
and summer seasons are presented, where the temperature varies significantly during the day and reaches higher levels. Statistics to investigate which environment factor has the major effect on the FSO performance was also investigated.