Performance of LoRaWAN CSMA in Dense LoRa Networks

LoRaWAN networks essentially overcome the low efficiency of ALOHA-based channel access method by relying on the frequency/Spreading Factor (SF) diversity and on the Adaptive Data Rate control mechanism. The Carrier Sense Multiple Access (CSMA) approaches were not considered by the LoRa Alliance until very recently when a LoRaWAN Technical Recommendation for enabling a CSMA protocol on LoRa networks was released, based on the Channel Activity Detection (CAD) mechanism. In this article, we study the performance and the scalability of the newly proposed LoRaWAN CSMA protocol with extensive simulations, in a very dense urban scenario and varying network topologies, radio and traffic conditions. We show that in such scenario the LoRaWAN CSMA has limited performance compared with a state-of-art multi-channel CSMA. We then propose gradual improvements of the LoRaWAN CSMA and thoroughly analyze their benefits.