## 6 Discussion  
Since the deployment of LoRaWAN for indoor and site-wide sensor data collection will become more common, this live site has provided some needed performance information. The site may not be typical in that the building was predominately open plan, and the outer skin was metal. However, the LoRaWAN range beyond the building indicated a wider scope of coverage in more complex buildings. The gateway positions in the building were chosen for their proximity to power and existing network connections, not for their optimal RF coverage, so planning for gateway installations is essential. As commercial gateways can be powered by power-over-ethernet and gateways can include mobile network backhaul, installations do not necessarily need to be limited by mains power or wired network availability. As the measurement site of approximately 80 hectares develops and more buildings are constructed, the probability is that the entire site could be covered, including sensors 'deep indoors, by two or three appropriately located external gateways. This appears very reasonable given the reception levels and packet success rates in the much larger and more complex Glasgow CBD environment also reported here. In Glasgow CBD environment, the height of the gateways relative to their surroundings was essential for getting good coverage down to sensors located near the ground level. One aspect of Glasgow CBD environment was the possibility of interference from other sources, including other ISM band technologies and other LoRaWAN installations. It is essential that LoRaWAN installations spread their traffic over as many channels as available to minimise congestion on core channels and co-channel interference. At the same time, interference should be minimised by implementing transmission power control in the motes to reduce the transmit power to the levels necessary for reliable connections. Since adaptive data rate is part of the LoRaWAN specification, newer endpoint products and NSs are expected to implement some power management. The measurement results from different locations in Glasgow CBD have shown varying signal activity occupying the 868 MHz ISM band. Table 7 shows the probability of LoRa signal interference for LoRA mandatory uplink and downlink Channels. The measurement sites were open spaces with the buildings in closer proximity except for Kelvingrove Park. While the measurement results in some areas showed a high probability of LoRa signal interference in the 868.0-868.6 MHz, this sub-band was not occupied at all in other locations. Figure 13: Measurements at Rottenrow Garden. The comparison of interference measurement results in this study with a recent study (four years old) [35] for interference in the 863-870 MHz ISM band for LoRa and Sigfox in the city of Aalborg, Denmark shows an increase in interference. While the highest probability of interference was at 33.7% in Aalborg, it is at 97.3% at GCU. All the measurement locations in Aalborg showed high interference presence in the 868.0-868.6 MHz for LoRa uplink, whereas areas like Buchanan Bus station in Glasgow CBD have no chances of LoRa signal interference. Surprisingly, the reported higher probability of LoRa signal interference at 58.2% in the Business Park in Aalborg four years ago in the 869.4-869.65 MHz sub-band is still the highest to Glasgow measurement locations. However, on average, the probability of LoRa interference is still more in Glasgow in the downlink compared to Aalborg. The probability of LoRa signal interference was independent of the 868.0-868.6 MHz sub-band transmission density. For instance, at GCU, the probability of interfering signals to affect LoRaWAN was 97.3% for LoRa uplink, and 4.8% for downlink was the highest, but fewer transmission signals were observed in the 868.0-868.6 MHz and 869.4-868.65 MHz. On the other hand, in locations with significant transmission density such as George Square and Kelvingrove Park, the probability of signal interference was at 13.2% and 64.9%, respectively, for mandatory LoRa uplink channels.