Simple and Efficient LoRa Receiver Scheme for Multi-Path Channel

TL;DR

This paper introduces a simple, efficient LoRa receiver scheme for multi-path channels using a matched filter approach, which enhances detection performance especially at low SNR and high spreading factors.

Contribution

The paper proposes a novel MF/RAKE receiver for LoRa in frequency selective multi-path channels, improving performance over existing methods with detailed complexity analysis.

Findings

Outperforms previous TDEL receivers in low SNR conditions.

Effective especially at higher LoRa Spreading Factors.

Provides practical recommendations based on complexity constraints.

Abstract

This paper presents a novel LoRa (Long Range) receiver operating in frequency selective Multi-Path Channel (MPC). The dechirped received LoRa wave-forms under MPC allows us to derive a simple and efficient LoRa receiver scheme by using a MF (Matched Filter) approach that aims to maximize the SNR (Signal-to-Noise Ratio) at the symbol index frequency of the DFT output. We show that the MF receiver can be seen as RAKE structure where interference peaks related to multipath, exhibited at DFT output, are recombined in a constructive way. Detection performance is driven by channel energy and the benefit of this novel MF/RAKE receiver over original coherent and non-coherent receiver appears only for MPC that exhibits significant paths energy. These two MF and RAKE receivers have however different implementation complexities that are studied in details. We provide in that sense recommendations on which receiver variant to use for real operations, depending on complexity constraints. Finally, the proposed MF/RAKE receiver outperforms previous results on TDEL (Time Delay Estimation LoRa) receiver over MPC, especially at low SNR and higher LoRa Spreading Factor (SF) parameter, at the cost of higher but reasonable complexity.