# An Efficient Adaptive Data-Link-Layer Architecture for LoRa Networks
## 5 Results and Discussion
In many cases, the end nodes are located in close enough proximity to the gateway, enabling them to communicate with a smaller SF while sustaining a reliable link to the gateway. By comparing the ToA of the lowest SF to the highest, we can see that an adaptive approach may decrease the ToA up to around nine times, resulting in much smaller energy consumption and use of the ISM band. On the other hand, if a fixed small SF value is used, we are not taking advantage of a larger link budget to support longer communication ranges when necessary or to overcome link quality fluctuations. In Figures 10 and 11, we can observe the relation between the sensitivity (where a lower value means more sensitive) and ToA for different spreading factors and CR fixed at 4/5. The four points of each curve/SF correspond to bandwidths of 125, 62.5, 41.7, and 31.25 kHz, respectively, from the top left to the bottom right of the graphs. The graphs \begin{table}
\begin{tabular}{l l l} \hline \hline
**Fields Name** & **Length (bits)** & **Value** \\ \hline Slot Allocation Request & 4 & 0 \(\times\) 0 \\ (Uplink) & 4 & 0 \(\times\) 1 \\ Slot Allocation Response & 4 & 0 \(\times\) 2 \\ (Downlink) & 4 & 0 \(\times\) 3 \\ \(\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{   \mathrm{  }}}}}}}}}}}}}}\) \\ \(\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ }}}}}}}}}}}}}}}}}\) \\ \(\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{{ \mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{\mathrm{ }}}}}}}}}}}}}}}}}}\) & 0 \(\times\) 0000000–0 \(\times\)FFFFFFF \\ Network Address & 16 & 0 \(\times\) 0001–0 \(\times\)FFFF \\ Short End Node Address & 8 & 0 \(\times\) 01–0 \(\times\) FFF \\ Superframe Period (s) & 16 & 0–65,535 \\ Superframe Synchronization & 16 & 0–65,535 \\ Field (s) & 16 & 0–65,535 \\ Data (Payload) & 32 & Application-specific \\ Options & 4 & 0–1 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Protocol applied to a real-world scenario. \begin{table}
\begin{tabular}{l l l} \hline \hline
**Metrics** & **T = 1000 ms** & **T = 4000 ms** \\ \hline Time on Air (ToA)—min \(|\) max (ms) & 97.5 \(|\)925.7 & 406.5 \(|\)3964.9 \\ Spreading Factor (SF)—min \(|\) max & 7112 & 7112 \\ Coding Rate (CR) & 4/5 & 4/5 \\ Bandwidth (Bw)—kHz & 125 & 31.25 \\ \(T_{parallel}\)—min \(|\) max (ms) & 68.9 \(|\)335.9 & 275.5 \(|\)1343.5 \\ \(N_{parallel}\)—min \(|\) max & 6163 & 6163 \\ Sensitivity—min \(|\) max (dB) & \(-121\)\(|\)\(-134\) & \(-127\)\(|\)\(-140\) \\ Max. Link Budget (dB) & \(-107\)\(|\)\(-120\) & \(-113\)\(|\)\(-126\) \\ Max. ASFS period (dB) & 132.1 & 528.4 \\ Min. time between messages—min \(|\) max (mm:ss) & 00.09 \(|\)01:32 & 003:90 \(|\)06:10 \\ Max. packets/day—min \(|\) max & 933 \(|\)8857 & 217 \(|\)2125 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results obtained with the LoRa parameter calculator. clearly show that both sensitivity and ToA increase as SF also increases, with the former increasing 2 to 3 dBm for each SF step up, while the latter increases very strongly as SF increases. Consequently, having smaller spreading factors when possible can heavily decrease ToA and, consequently, energy consumption. In case smaller values of CR are used (4/6 through 4/8), ToA increases (as is shown in Figures 12 and 13), but the sensitivity is not affected. Figures 12 and 13 show the relation between the coding rate and ToA for different spreading factors, where Bw is fixed at 125 kHz, where we can conclude the ToA increases proportionally with each increase in CR and that the extra error correction provided by the coding rate might be worth the extra ToA and power consumption. Figure 11: Relation between sensitivity and ToA for SFs 10 through 12, with CR = 4/5 and \(\text{Bw}\in\{125,\,62.5,\,41.7\) and \(31.25\}\) kHz.