# LoRaWAN Base Station Improvement for Better Coverage and Capacity
## 4 Results
### Prototype Validation  
The analysis of messages obtained from the measurements showed that even without the metal surface behind the antennas, the novel base station with two concentrators received more messages than the single base station. Specifically, in the same period of time (in 5 h), base station with two antennas without metal surface (case C) received 98.7% of all messages that base stations received combined. On the other hand, base station with one antenna received 76% of those messages which means that the second set of concentrator and antenna increased the probability of successful transmission. This is a very valuable improvement since it is important for energy efficiency of the entire network as LPWAN networks in most cases work with battery-powered devices. When the metal surface was added (case D), number of messages received on both base stations increased by 25% (from 2235 to 2797 messages). As expected this increase shows that adding the metal surface improved base station directivity and thus also the range. The percentage of the messages received on the novel base station remained the same as in the first case but that percentage decreased for the standard single antenna base station (67%) which indicates that the novel base station received more messages with the metal surface set behind the antennas. Table 2 shows the percentage of received messages on each base station. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Novel Base Station** & **Standard Base Station** & **\# Messages** \\ \hline
98.7\% (case C) & 76.3\% (case A) & 2235 \\
98.1\% (case D) & 67.2\% (case A) & 2797 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Number of messages received by each base station. Figure 5: Base station use cases: Case A is used as reference (standard single antenna base station) in comparison with novel base station design possibilities (cases B, C and D). For the second part of novel base station model validation we used the aforementioned LoRaWAN end node to test the improvement when the metal surface is set behind the antenna. For comparison, we set the metal surface behind the antenna of one base station (case B) while the other was the standard one (case A). All components used in the development of both base stations were the same. The end node was programmed to send six messages with different spreading factors. Bandwidth was set to be 125 kHz and payload size 3 B so that communication parameters only depend on spreading factor and distance from the base stations. The end device sent 12 messages (two series of six messages (for SF7 to SF12)) from each of 6 locations set approximately 1-2 km away from the building with the base stations in the dense urban area of Zagreb, Croatia. Since the focus was to evaluate the impact of metal surface for sector radiation purposes, all end device locations were set in the same sector as shown in Figure 6.  
The results showed that base stations received 86% of the messages (31 of 36) sent by end device. In 80% of them (25 of 31) the base station with metal surface behind the antenna received with higher RSSI than the standard one. In some cases, the difference between RSSIs was 9 dB which could be significant for extended range. Regarding spreading factor, as shown in Figure 7, mean RSSI is higher for each spreading factor on base station with directed antenna (with metal surface behind the antenna). The biggest difference can be seen for SF8 where the increase of mean RSSI is around 3 dB while the smallest one is for messages sent with SF7. In order to evaluate RSSI for different spreading factors while keeping the distance between base stations and end device relatively short (urban environment), ADR had to be disabled (otherwise the ADR algorithm would always use SF7 or SF8) and spreading factor set manually for each LoRaWAN message. Figure 6: Test end device locations in city of Zagreb, Croatia set approximately 1 to 2 km from the base stations.