# EEMIP: Energy-Efficient Communication Using Timing Channels and Prioritization in ZigBee
## 4 Results and Discussion
### Evaluation of Scenario C  
In this scenario, the data for each packet transmission were generated pseudorandomly, with a size of 1-10 bytes (i.e., a common sensor-data size). The end devices were started one at a time with a delay of 50 ms (i.e., the device 1 was started at a time T, the device 2 was started at a time T + 50 ms, the device 3 was started at a time T + 100 ms, etc.). The high-priority time interval was set to 2 s and the low-priority time interval was set to 10 s. Each end device had both, the low priority data and high priority data. To simulate occasional retransmissions (e.g., interference/collision), each 50 th packet was lost. We have conducted three measurements in this experiment (each taking one hour) and used the average values in the reported tables. Table 9 report the results of such an experiment. The first column represents a device identifier. The second and third columns represent the number of processed bytes and packets, respectively, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Each 3 rd Packet Lost**} & \multicolumn{3}{c}{**Each 5 th Packet Lost**} \\ \cline{2-7}
**End** & **2 s** & **3 s** & **5 s** & **2 s** & **3 s** & **5 s** \\
**Device** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** \\
**ID** & **Time Interval** & **Time Interval** & **Time Interval** & **Time Interval** & **Time Interval** & **Time Interval** \\ \hline
1 & +51.63\% & +73.67\% & +63.06\% & +50.00\% & +28.69\% & +29.65\% \\
2 & +19.82\% & +36.06\% & +24.55\% & +23.27\% & +15.26\% & +9.91\% \\
3 & +22.27\% & +32.23\% & +26.98\% & +15.20\% & +5.65\% & +3.65\% \\
4 & +20.40\% & +22.89\% & +15.23\% & +6.39\% & \(-2.27\%\) & \(-3.09\%\) \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Comparison of the two simulation modes for congestion conditions. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Each 3 rd Packet Lost**} & \multicolumn{3}{c}{**Each 5 th Packet Lost**} \\ \cline{2-7}
**End** & **2 s** & **3 s** & **5 s** & **2 s** & **3 s** & **5 s** \\
**Device** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** & **Low-Priority** \\
**ID** & **Time Interval** & **Time Interval** & **Time Interval** & **Time Interval** & **time interval** & **Time Interval** \\ \hline
1 & +31 & +45 & +38 & +30 & +18 & +18 \\
2 & +12 & +22 & +15 & +14 & +10 & +6 \\
3 & +14 & +20 & +17 & +10 & +4 & +3 \\
4 & +13 & +14 & +10 & +4 & \(-2\) & \(-2\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Time comparison (in minutes) of the two simulation modes for congestion conditions. for the nonbeacon ZigBee simulation. Similarly, the fourth and fifth columns refer the same for EEMIP simulation mode. The last two columns represent the comparison between the two simulation modes. From the results, we can notice a decrease in the number of processed bytes by 40% on average, when using EEMIP. On the other hand, we can see that the number of transmitted packets is increased by 22%. The number of transmitted bytes is lower in the case of EEMIP because it sends low priority data less frequently. The nonbeacon ZigBee does not deal with priorities, thus, it must send both high and low priority data with the higher frequency. The number of packets is higher in case of EEMIP due to control overhead and the fact that the low priority data are sent in dedicated messages (i.e., separated from the high priority data). Although the number of packets is increased, the reduction in the number of processed bytes is the key indication that the EEMIP method increases energy efficiency in a realistic scenario even more than than previous boundary-cases experiments. Using the same setup, we have executed another experiment, in which we have scaled the amount of congestion (from occasional to more frequent). This experiment is used to illustrate how the data transmission efficiency is affected by the congestion, comparing nonbeacon ZigBee and EEMIP methods.