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.

Coherent Multi-channel Ranging for Precise Localization in Narrowband LPWA Networks: Performance Trials in an Indoor Environment

“…, where f R is a constant carrier frequency, ∆f the channel spacing and C the number of channels [7]. Fig.…”

“…This technique, based on multiple phase measurements or Phase of Flight (PoF), significantly improves temporal resolution and ranging precision, while preserving the narrowband modulation necessary for long-range communications. Performance evaluation of PoF measured through field trials has already proved its potential in an outdoor environment [7]. In a urban environment strong biases have been observed and a ranging bias estimator has been introduced to detect Non-Line-Of-Sight (NLOS) propagation conditions [7].…”

“…Performance evaluation of PoF measured through field trials has already proved its potential in an outdoor environment [7]. In a urban environment strong biases have been observed and a ranging bias estimator has been introduced to detect Non-Line-Of-Sight (NLOS) propagation conditions [7]. However, evaluation of performance of the PoF technique in an indoor environment has so far not being performed, this is however fundamental for the targeted wearable health monitoring application.…”

Multi-Frequency Phase Difference of Arrival for Precise Localization in Narrowband LPWA Networks

“…A new technique, called coherent multi-channel ranging, has therefore been proposed to significantly improve precision. It relies on multiple narrowband signals that are sequentially transmitted on different and discontinuous channels to virtually increase the bandwidth [4] [5]. This technique, based on multiple phase measurements or Phase of Flight (PoF), significantly improves temporal resolution and ranging precision, while preserving the narrowband modulation necessary for long-range communication.…”

“…This technique, based on multiple phase measurements or Phase of Flight (PoF), significantly improves temporal resolution and ranging precision, while preserving the narrowband modulation necessary for long-range communication. The technique has been so far evaluated in two-way ranging scenarios, where elements (nodes or base-stations) sequentially perform a two-way packet exchange in order to remove absolute time synchronization constraints [4] [5]. When LPWA base stations are strictly synchronized using e.g.…”