Scalability analysis of multiple LoRa gateways using stochastic geometry

Low-Power Wide Area Networking (LPWAN) technology offers long-range communication, enabling new types of services for Internet-of-Things (IoT). While LPWAN solutions are proliferating verticals at tremendous pace, little attention has been paid to scalability and performance analysis of such networks. Hence, it is of utmost importance to analyze how well these technologies will scale as the number of connected devices grows in future. Several technologies are associated with LPWANs, but Longe Range WAN (LoRaWAN) is the most adopted LPWAN technology worldwide. It promises ubiquitous connectivity in outdoor IoT applications while keeping network structures and management as simple as possible. Consequently LORAWAN has received a lot of attention in recent time from network providers. In this letter, we first perform the system level outage analysis of a single LoRa gateway by using the chirp spectrum modulation scheme. We then extend our investigation to multiple gateway scenario and show that the coverage probability reduces exponentially when the number of gateways increases due to the presence of more interfering signals from different nodes using the same spreading sequence. We conclude that this fundamental limiting factor is perhaps more significant towards LoRa scalability. Our derivations for co-spreading factor interference found in multiple LoRa gateways enables demand of scalability analysis of such networks.