Theoretical and Practical Evaluation of LoRa-Based Ranging Toward Accurate TDoA-Based LoRa Localization

Conventional Internet of Things (IoT) technologies such as RFID, Bluetooth, and Wi-Fi exhibit compromise between energy-efficiency and communication range. Long Range (LoRa) technology is pillared on guaranteeing battery lifetimes for up to ten years while promising reliable communication at the scale of ten kilometers. Such capabilities exhibit an exclusive potential of LoRa to proliferate a vast set of localization-based IoT use cases. This letter evaluates the theoretical and practical capabilities of LoRa-based distance ranging which is a fundamental constituent of Time Difference of Arrival (TDoA)-based localization. The letter first derives the theoretical Cramer-Rao Lower Bound (CRLB) for ranging of LoRa signals. A simulation model is then developed that incorporates practical reception aspects such as frequency offset estimation errors. The distance errors attained from simulations are compared against the theoretical bounds and the impact of frequency offsets is evaluated. Furthermore, an experimental Software Defined Radio (SDR) setup is devised for practical evaluation of distance ranging over a span of Signal-to-Noise Ratio (SNR) values.