Coherent Multi-Channel Ranging for Narrowband LPWAN: Simulation and Experimentation Results

Abstract

Precise radio based positioning for low power wide area networks remains a challenging research area due to narrowband signals and multipath propagation. Multi-channel ranging provides improved temporal resolution by coherent processing. While this technique has been applied to short range radio standards, no experimental demonstration for long range radio devices exists. The present paper introduces a hardware testbed for phase coherent multi-channel processing of narrowband signals. Simulations and preliminary experimental multi-channel results show a higher ranging precision (factor 20) over time based ranging. In a frequency flat channel with a 10 kHz signal, precisions down to 10 m (phase based) and 200 m (time based) have been achieved. Precision degrades in multipath propagation scenarios.

Benchmarking of Narrowband LPWA Physical Layer Ranging Technologies

“…For such a processing scheme, range resolution is conditioned by the virtual bandwidth BW virt and is given by ∆R = c 0 /(2(C − 1)∆f ) = c 0 /(2BW virt ) and maximum unambiguous range R max = c 0 /(2∆f ) [17]. Details on this method can be found in [11], [13].…”

“…Existing work [8]- [10] only provides few benchmarking of the ranging feature. Coherent multi-channel ranging allows improving temporal resolution through the aggregation of sequentially transmitted narrowband signals [11]. This technique is compatible with LPWA constraints and offers advanced geolocalization.…”

“…Various studies [12]- [14] have demonstrated the performance gain compared to ToF ranging. An implementation for LPWA networks [11] is hereafter denoted Coherent Ranging On Narrowband Enabled Networks (CRONEN).…”

“…The present work compares LPWA adapted multi-channel ranging with CRONEN [11], to the LoRa 2.4 GHz SX1280 ranging feature [7], in the absence of a comparable ranging system in the 868 MHz ISM band. Focus lies on ranging accuracy and precision.…”

Time Delay Estimation Based on Multi-band Multi-carrier Signal in Multipath Environments

“…Xu et al [3] average the channel estimates from different signal bands to obtain better estimation results. Wolf et al [4] proposed a multi-channel ranging protocol for low power wide area network (LPWAN) by aggregating sequentially transmitted narrowband signals. The propagation delay is retrieved from the estimated channel impulse response after ordinary inverse Fourier transform.…”