Reliable and Energy-Efficient Reprogramming for Smart LoRaWAN

As a promising low-power wide-area network communication technology, Long Range Wide Area Networks (LoRaWAN) have been widely adopted by smart applications, such as smart metering, smart grids and smart cities. In these applications, massive deployed end devices demand reprogramming with the latest standards and preventing security vulnerabilities through their life cycle, which makes reprogramming a crucial issue. The existing reprogramming scheme in LoRaWAN, called LoRaWAN firmware update over-the-air (FUOTA), suffers from inefficient firmware dissemination and computation-intensive coding. Moreover, considering the topology difference and unique physical layer parameters (e.g., spreading factors) of LoRaWAN, classical reprogramming schemes in wireless sensor networks are not suitable for LoRaWAN. To address this challenge, we propose a reprogramming scheme called DAU (Divide And Upgrade) for LoRaWAN. To ensure reliability, we exploit the channel activity detection (CAD) technique to effectively detect negative acknowledgments (NACKs) from devices and use a lightweight coding scheme to reduce computing and storage overhead. Besides, devices are divided into groups using different spreading factors (SFs) to reduce network energy consumption. To further reduce the setup time of reprogramming, we leverage the beacons of LoRaWAN to quickly disseminate the meta-data of firmware to devices participating in the reprogramming. Extensive experimental results based on outdoor testbed demonstrate that DAU can significantly reduce energy consumption compared to FUOTA.