# Combined Use of LoRaWAN Medium Access Control Protocols for IoT Applications
## 5 Network Configuration and Performance Metrics  
In this paper, we investigate how to take advantage of using, on the same network, both the MAC protocols available for LoRaWAN when they work in accordance with the ETSI norms. In our model, a group of end-devices uses Pure ALOHA while the other group adopts LBT AFA. To combine the use of the two protocols, we envisaged two possible approaches. The first one does not impose any constraint on how the two protocols are configured, while in the second case, channel separation is adopted. The first approach, here called the SHC (SHared Channels) scenario, involves a LoRaWAN network in which the end-devices that use Pure ALOHA and those that use LBT AFA work on the same channels. In the second approach, here called the SPC (SPlit Channels) scenario, the channels available for transmissions are split into two different sets. This way, in the same LoRaWAN network, the group of end-devices that use the Pure ALOHA MAC protocol exploits a set of channels, while the other group of end-devices runs LBT AFA on the other set of channels. In particular, for the SPC scenario, we consider two configurations of channels (here called Configuration A and Configuration B) that differ for the number of channels used by the two considered MAC protocols. In the SHC scenario, all the end-devices operate on the same set of channels, as shown in Table 3.  
From Table 3 it is possible to obtain the overall duty cycle of each end-device that uses Pure ALOHA or LBT AFA (i.e., 12.1% and about 19.46%, respectively) as the sum of the duty cycle values of each used channel. Tables 4 and 5 show the channels used by the end-devices in the configurations A and B of the SPC scenario according to the MAC protocol used. In particular, in Configuration A (shown in Table 4), each end-device that adopts Pure ALOHA operates on four channels and can achieve an overall duty cycle of 11%, while \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Limit** \\ \hline \(\Delta_{CCA}^{min}\) & 160 \(\upmu\)s \\ \hline \(\Delta_{def}^{min}\) & CCA interval (\(\Delta_{CCA}\)) \\ \hline \(\psi_{A_{def}}^{min}\) & Declared by the manufacturer \\ \hline \(\Theta_{CCA\_I,xx}^{max}\) & 5 ms \\ \hline \(ToA_{rx}^{max}\) & 1 s \\ \hline \(\Lambda_{rx}^{max}\) & 4 s \\ \hline \(\mathcal{DC}_{200 kHz}^{max}\) & \(\approx\)2.78\% \\ \hline \(\mathcal{T}_{Off\_Time}^{min}\) & 100 ms \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Timing parameters of polite medium access based on LBT AFA. each end-device that uses LBT AFA works on three channels and can reach a duty cycle up to about 8.34%. In Configuration B of the SPC scenario (shown in Table 5), the end-devices that use Pure ALOHA exploit three channels and can achieve an overall duty cycle of 11%, while those that adopt LBT AFA work on four channels and can reach a duty cycle of about 11.12%. In this work, the above-mentioned scenarios and configurations are evaluated against the performance metrics that are defined in the following subsection. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**MAC Protocol**} & \multirow{2}{*}{**Sub-Band**} & \multicolumn{2}{c}{**Channel Frequency (MHz)**} & \multirow{2}{*}{\(\mathcal{DC}^{max}\)} \\ \hline \multirow{4}{*}{Pure ALOHA} & \multirow{2}{*}{h1.4} & 868.10 & \multirow{2}{*}{1\%} \\  & & 868.30 & & \\  & & 868.50 & & \\ \cline{2-3} \cline{5-5}  & \multirow{2}{*}{h1.6} & 869.525 & 10\% \\ \cline{2-3} \cline{5-5}  & & 868.80 & & \\ \cline{2-3} \cline{5-5}  & & 869.10 & & \\ \cline{2-3} \cline{5-5}  & & 869.10 & & \\ \cline{2-3} \cline{5-5}  & & 869.85 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: SPC scenario—Configuration A.