Phase-based Ranging in Narrowband Systems with Missing/Interfered Tones

TL;DR

This paper introduces two phase-based ranging methods for narrowband systems that effectively handle missing or interfered tones, utilizing neural networks to maintain high accuracy with minimal additional complexity, suitable for low-cost radios like BLE.

Contribution

It proposes novel phase-based ranging schemes that address missing/interfered tones using neural networks, achieving near-reference accuracy with low complexity and memory overhead.

Findings

Neural network-based scheme performs close to ideal systems with missing tones.

Proposed methods require negligible additional computational complexity.

System is suitable for hardware-limited radios like BLE.

Abstract

The growth in the number of low-cost narrow band radios such as Bluetooth low energy (BLE) enabled applications such as asset tracking, human behavior monitoring, and keyless entry. The accurate range estimation is a must in such applications. Phase-based ranging has recently gained momentum due to its high accuracy in multipath environment compared to traditional schemes such as ranging based on received signal strength. The phase-based ranging requires tone exchange on multiple frequencies on a uniformly sampled frequency grid. Such tone exchange may not be possible due to some missing tones, e.g., reserved advertisement channels. Furthermore, the IQ values at a given tone may be distorted by interference. In this paper, we proposed two phase-based ranging schemes which deal with the missing/interfered tones. We compare the performance and complexity of the proposed schemes using simulations, complexity analysis, and measurement setups. In particular, we show that for small number of missing/interfered tones, the proposed system based on employing a trained neural network (NN) performs very close to a reference ranging system where there is no missing/interference tones. Interestingly, this high performance is at the cost of negligible additional computational complexity and up to 60.5 Kbytes of additional required memory compared to the reference system, making it an attractive solution for ranging using hardware-limited radios such as BLE.