Accurate narrowband LPWA ranging: Principles, performance in AWGN and multipath channels

Abstract : 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.