CEC-LoRa: A Codeless Error Correction Method for Corrupted LoRa Packet Decoding

For various wireless sensing and IoT applications, LoRa has emerged as an energy-efficient and long range solution for wireless data transfers. However, real-world deployments face multiple challenges, including packet collisions and variable link qualities, which generally lead to packet corruptions and data loss. Even though LoRa relies on forward error correction to restore corrupted packets, its usage comes with a significant energy overhead and only provides limited capabilities. In our paper, we present CEC-LoRa as an alternative to LoRa’s forward error correction feature. Its key innovation is that CEC-LoRa allows to restore corrupted packets without any error correction codes. Our approach exploits two symbiotic properties in LoRa’s encoding and chirp-based modulation scheme. On the one hand, misinterpreted chirps are often confused with neighboring symbols. On the other hand, neighboring symbol values only differ by one, keeping high similarity between misinterpreted and correct symbols. We leverage these properties by pre-computing a set of all plausible LoRa packets based on the expected payload permutations and compare them with the received packet. This allows us to identify the closest match and thus the most probable candidate packet. While the pre-computations incur a quite substantial energy overhead, CEC-LoRa shifts this from the energy-constrained end devices to the receiver side. The benefits greatly outweigh the energy demand, though: CEC-LoRa reduces the number of corrupted packets by 86.5 % on average without any additional overhead on the end device and while still being fully compliant to the LoRa specification. By including symbol information, CEC-LoRa can reduce the number of corrupt packets even further, by 99.5 % on average. This translates into SNR gains in the range of 0.79 dB to 0.93 dB.