Delta-Based Compression and Multicast Synchronization for Efficient LoRaWAN FUOTA

Remote firmware updates in LoRaWAN are a fundamental component for maintaining edge devices. When energy is a limited resource and downtime must be minimized, standard over-the-air firmware updates may not provide an optimal solution. This paper proposes two approaches to address LoRaWAN’s restricted data rate. The first strategy builds on an open-source tool tailored to resource-constrained microcontrollers, which reduces the amount of data to be transmitted by generating compact delta scripts. The proposed compression relies on flexible bit-length opcodes that reduce the delta-script size while keeping firmware reconstruction lightweight, achieving an average reduction of approximately 15-20 times compared to transmitting the full image, for minor code changes. The second strategy introduces a protocol that synchronizes nodes starting from Class A and activates the radio only during scheduled fragment transmissions, improving normal multicast sessions where devices remain continuously in Class C. Despite LoRaWAN latency and timing variability, experimental results show that devices can be synchronized to optimize radio activity. The two strategies can be combined to reduce both energy consumption and update duration, while the second method enables fine-grained tuning of the trade-off between campaign time and network load.