A Novel Autonomous Time-Slotted LoRa MAC Protocol with Adaptive Frame Sizes

Time-Slotted Medium Access Control protocols bring advantages to the scalability of LoRa networks as an alternative to the ALOHA access method. However, such Time-Slotted protocols require nodes synchronization and schedules dissemination under stringent duty cycles likely resulting in improper performance and limited scalability. One possible solution is to adopt decentralized approaches where nodes autonomously determine their schedules and other transmission parameters. Thus, this paper proposes a novel Time-Slotted MAC protocol, named Autonomous Adaptive Frame Size (AAFS-LoRa) protocol, that allows nodes to individually determine their transmission parameters without extensive downlink transmissions from the gateway. The proposed protocol can conFigure nodes by maintaining information, such as their location and the gateway location. The main contribution of the proposed protocol is the adoption of adaptive frame sizes that are large enough to accommodate nodes with common transmission parameters to mitigate collisions among them. The proposed protocol has been investigated under different operating conditions, and the experiments demonstrates that our protocol can effectively improve the network performance, in terms of latency as well as the capacity.