# Implementation of an IoT Based Radar Sensor Network for Wastewater Management
## 3 Implementation and Results
### LoRaWAN Radar Network Deployment
#### 3.2.2 Results  
A heat map of this initial radio channel ranging survey has been produced for the Shoalhaven region. Additionally, a prototype end device utilising the LoRaWAN protocol has been installed within Shoalhaven Water's WCN to effectively monitor manhole SPS levels and flows.  
(a)_LoRaWAN Network Capabilities_  
Figure 19: Prototype LoRa radar sensor device (**a**) Flow of operation, and (**b**) Interface board.  
Further analysis was performed on results collected from the Shoalhaven region network survey, and data received from the radar sensor node in a manhole upstream to the previously tested SPS Site B.  
The radio channel ranging device design above allowed for a comprehensive heat map of signal characteristics to be produced for the Shoalhaven region; showing maximum transmit distances localised to the region's geographic area, as well as the corresponding signal statistics. The incrementing counter sent from the MCU allowed a calculation of throughput over expanding radii.  
**Throughput:**  
Of a total 3100 packets sent, 2911 were successfully received by the gateway. Separating sampled data into expanding regions from the gateway however, demonstrates the effect of both distance, land topography and obstructions on signal throughput.  
Table 2 below shows that as distance from the gateway is increased, the mean signal-to-noise ratio (SNR), received signal strength indicator (RSSI) and throughput all decrease, as expected.  
Based on the above results, a heat map of this survey has been produced for the Shoalhaven region. Shown in Figure 20 below on the it can be seen that the majority of the Berry, Bomaderry, Nowra and South Nowra town centres are effectively serviced by this single gateway, with its reach extending as far as Gerringong to the North, Culburra to the East and Vincentia to the South. The Shoalhaven Heads township however is blocked from communications due to both Coolangatta Mountain and Moeyan Hill. Callala Bay and surroundings are blocked by the dense vegetation of the Currambene State Forest and Jervis Bay National Park.  
To service these areas and avoid obstructions, an additional gateway is required on an alternative radio tower within range.  
(b) _Radar Sensor Node_  
Utilising the Cayenne LPP encoding scheme, the developed radar sensor device installed is capable of measuring the instantaneous well fill levels and calculating the corresponding derived flow rates. Both the well fill level and derived flow rate are transmitted via the LoRaWAN network and uploaded to the cloud-based platform; Cayenne IoT Project Builder Web Interface.  
Currently transmitting derived values after a level deviation of 5%, the free Cayenne IoT Project dashboard provides not only an effective web-based tool to monitor any LoRaWAN devices deployed out in the field, but also offers a mobile app with close to the same functionality. On overview of the dashboard is shown in Figure 21 below.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Distance (km)**} & **Packets** & **Packets** & **Mean SNR** & **Mean RSSI** & \multirow{2}{*}{**Throughput**} \\  & **Received** & **Sent** & **(dB)** & **(dBm)** & \\ \hline
**d \textless{} 5** & 364 & 372 & 2.86 & \(-98.73\) & 97.8\% \\
**5 \textless{} d \textless{} 10** & 1150 & 1184 & \(-0.96\) & \(-106.62\) & 97.1\% \\
**10 \textless{} d \textless{} 15** & 1133 & 1200 & \(-3.77\) & \(-107.64\)Figure 22 below displays both the SNR and RSSI for each packet received by the Cambewarra gateway over a full-day period. It is shown that most packets arrive close to the mean SNR and RSSI of 3.42 dB and \(-100.65\) dBm, respectively.  
Figure 20: Shoalhaven region radio channel ranging survey.  
Figure 21: Cayenne IoT Project Builder.  
The daily signal statistics shown in Figure 23 below demonstrate that while all packets received were within acceptable range, there were a number of packets received that were well below the noise floor. All outliers for RSSI were, in fact, of clearer reception.