Experimental Insights into the Performance of LoRa/LoRaWAN Radio Interface in Smart City Deployments
Authors: Pires Luis , Martins José 
Published: November 2024

IoT ecosystem extends beyond country borders and application domains, combining thousands of versatile devices that differ in terms of their structures, capabilities, and available resources. It is therefore not surprising that the landscape of wireless communication technologies and the degree of IoT devices available today is excessively broad and diverse and the reliability of LoRaWAN networks can be affected by factors such as collisions, interference, and varying signal strengths. Interference between networks leads to frame collisions and consequent packet loss. Frame colli-sions occur when two or more packets overlap in time and frequency and use the same Long Range (LoRa) parameters, i.e. the same Spreading Factor (SF), Bandwidth (BW) and Carrier Fre-quency (CF). When most devices use the same configuration, collision probability is higher. The probability of frame collisions is also affected by traffic characteristics, particularly the periodicity of the transmission and the payload size. Larger payload sizes and more frequent transmissions accumulate with higher Time on Air (ToA) and channel occupancy [1]. Transmission powers and the location of the gateways also influence this situation. The aim of this experimental work is to verify the effects of collisions and interference in Long Range Wide Area Network (LoRaWAN), focusing on how SFs and payload sizes influence signal transmission quality in an inter-SF interfe-rence scenario. This research is crucial for smart cities, where numerous IoT devices are deployed to monitor and manage urban infrastructure. Reliable and efficient communication networks are essential for the seamless operation of Urban IoT (UIoT) systems. In this context, the integration of IoT, along with other systems such as cyber-physical systems and cloud computing, necessitates robust and scalable communication networks to ensure efficient data transmission and network reliability. LoRaWAN, with its long-range and low-power capabilities, is already a widely adop-ted technology for connecting numerous devices and can be seamlessly integrated across large ur-ban environments. In such environments, inter-SF interference can significantly impact the per-formance of LoRaWAN networks. The choice of SFs and packet lengths directly affects ToA. When multiple devices operate near gateways, using different SFs and varying packet lengths can lead to increased latency and longer ToA. This, in turn, raises the risk of packet loss, especially in scenarios with a low signal-to-interference ratio (SIR). Such limitations pose challenges to the sca-lability of the network, particularly in Non-Line-Of-Sight (NLOS) situations, where obstacles like vegetation or buildings (or field walls) can further degrade signal quality. Our work validates me-asuring performance indicators like Received Signal Strength Indicator (RSSI), ToA, and Packet Delivery Ratio (PDR) to assess network reliability. By analyzing ToA in relation to RSSI and diffe-rent data sizes, and examining RSSI for different SFs and data sizes, we gain a comprehensive understanding of the network’s performance. Additionally, we evaluate packet loss through PDR to understand the reliability of packet transmission. These metrics are essential for optimizing the performance and reliability of LoRaWAN networks, which will impact various smart city applica-tions such as environmental monitoring, smart metering or smart buildings.
We conclude that in an environment with inter-SF interference, the choice of SFs and packet len-gths impacts ToA, leading to packet loss in the NLOS scenario.