Over-the-air (OTA) updates
OTA updates enable IoT devices to receive and install software or configuration updates without the need for physical access to the devices. This mechanism is supported across a variety of embedded operating systems, including embedded Linux and FreeRTOS, and can be powered by the AWS IoT Jobs agent and cloud service .
The OTA update mechanism for IoT devices must be resilient, reliable, and secure in order to help prevent a failed update from requiring a truck roll to fix the device. There are several techniques that device makers can use to build a resilient OTA mechanism.
OTA updates may encounter errors or failures during the update process, such as network errors, data corruption, or other issues. The device's firmware should have error handling and recovery mechanisms in place to detect and recover from potential errors, such as checksum verification, error correction codes (ECC), redundancy, or other suitable techniques to support data integrity and reliability.
Atomic updates are updates that are either fully applied or fully rolled back, without leaving the system in an inconsistent state. This can be achieved by storing a new version of the firmware on an inactive partition and then swapping it with the active firmware partition upon successful completion. This approach also supports safe roll-back in case the new firmware encounters errors.
Once an OTA update is installed and running correctly, the device must help prevent it from being rolled back to a previous vulnerable version. This can be achieved through mechanisms such as secure bootloaders, cryptographic signatures, or other techniques that help prevent the device from reverting to older, potentially less secure firmware/software versions.
OTA updates can also be used for certificate rotation when there is a security incident or to renew an expiring certificate. A certificate rotation mechanism extends the device's lifetime without the need to use long-lived certificates and allows the device to benefit from improvements in security algorithms and ciphers that might not have been available at the time the device was manufactured.
Devices on networks such as LoRaWAN and NB-IoT face additional
challenges. These networks are constrained in bandwidth,
making OTA updates power inefficient for large file transfers.
Sending large files over the air is also problematic for
battery-powered devices connected to more power-hungry Wi-Fi
and cellular networks. To overcome this issue, instead of
sending the entire firmware image to a device, send only the
portions of the image that have actually changed, reducing
communication and processing required, and reducing power
consumption.
The Delta
Over the Air Updates
