FragCast: A Scalable BLE‐Based OTA Framework for Constrained IoT Devices

ABSTRACT

The proliferation of constrained Internet of Things (IoT) devices requires scalable over‐the‐air (OTA) firmware update mechanisms. Conventional approaches, predominantly based on one‐to‐one communication, such as Bluetooth Low Energy (BLE) Device Firmware Update (DFU), suffer from a scalability bottleneck that makes fleet‐wide updates inefficient and energy‐intensive. To address this limitation, this paper proposes FragCast, a broadcast‐based OTA dissemination protocol that leverages the one‐to‐many communication paradigm of BLE advertising channels. The proposed solution implements an application‐layer protocol that transports firmware fragments within custom‐formatted BLE advertising packets. A detailed simulation framework was developed to analyse the protocol performance under different scanning profiles and fleet sizes of up to 100 devices. The proposed mechanism was also experimentally validated on Arduino UNO R4 Wi‐Fi boards equipped with ESP32‐S3 modules. Results show that the broadcast architecture enables efficient fleet‐wide dissemination, with discovery latency remaining nearly constant as the number of receivers increases. In the evaluated configuration, a fleet of 100 devices can be updated in approximately 40 s using the Aggressive scanning profile and about 90 s using an energy‐efficient iOS‐like profile. These findings demonstrate that BLE advertising provides a practical and scalable foundation for OTA firmware dissemination in large fleets of constrained IoT devices.