Evaluation of Relay Functionality in LoRaWAN: Energy Consumption Trade-offs and Oscillator Accuracy

Long-range wide-area network (LoRaWAN) deployments are limited by the protocol’s native star topology. In obstructed environments, such as underground, dense urban, or industrial sites, coverage can be unreliable, causing data loss. Adding gateways improves coverage but is often cost-prohibitive. To address this, the long-range (LoRa) alliance introduced the relay functionality. This letter analyzes the energy impact on relays and end-devices using time-on-air (ToA)-based estimates, comparing LoRaWAN relay performance with the long-preamble method and emphasizing tradeoffs and oscillator accuracy. Our analysis reveals that the tolerance of the crystal oscillator plays a major role in the end device’s energy consumption. Specifically, using a 10-ppm crystal instead of a 40-ppm crystal, the standardized mode provides a 29% energy reduction for SF7 values compared to the long-preamble approach for a 1-h link periodicity. © 2014 IEEE.