Accurate Narrowband LPWA Ranging: Principles, Performance in AWGN and Multipath Channels

Today approaches of radio localization for Low Power Wide Area networks do not provide sufficiently accurate ranging required by applications such as wearable health monitoring. Coherent multi-channel ranging or Phase-of-Flight (PoF) ranging provides significantly improved temporal resolution through the aggregation of sequentially transmitted narrowband signals for the same level coverage performance as legacy Time-of-Flight (ToF) ranging. This paper compares the performance of PoF and ToF under additive white Gaussian channels with both simulations and laboratory measurements. Field trials have been performed in a multipath outdoor environment and strong ranging biases are observed. Ranging bias estimators are introduced and evaluated to mitigate these damaging effects: thanks to the new approach, accuracy of 30 m in 90% of the cases may be obtained. This compares to 250 m when legacy ToF is considered.