Reliability and Energy Consumption of LoRa With Bidirectional Traffic

We analyze the reliability and energy consumption of uplink message delivery in bidirectional LoRa networks that employ acknowledgements and retransmissions. Our frame-collision analysis with symbol-level timing accuracy shows that the ACKs—introduced to improve reliability—significantly impact the end devices’ power consumption via the collisions they introduce. We demonstrate that a critical design parameter affecting reliability and energy consumption is the maximum number of times an end device retransmits an unacknowledged frame. Our analytical framework can be used to appropriately choose this parameter by taking node density, traffic intensity, target reliability, and the energy budget into account.