Performance Improvement of LoRa Modulation with Signal Combining and Semi-Coherent Detection

TL;DR

This paper explores how using multiple antennas and advanced detection techniques can significantly enhance LoRa system performance, increasing coverage and reducing power needs in long-range, low-power communications.

Contribution

It introduces optimal decision rules for signal combining in LoRa, analyzes error probabilities, and proposes a semi-coherent detection method that approaches coherent detection performance without CSI overhead.

Findings

Large power gains achieved with multiple antennas

Semi-coherent detection approaches ideal coherent detection

Coverage extension demonstrated through simulations and analysis

Abstract

In this paper, we investigate performance improvements of low-power long-range (LoRa) modulation when a gateway is equipped with multiple antennas. We derive the optimal decision rules for both coherent and non-coherent detections when combining signals received from multiple antennas. To provide insights on how signal combining can benefit LoRa systems, we present expressions of the symbol/bit error probabilities of both the coherent and non-coherent detections in AWGN and Rayleigh fading channels, respectively. Moreover, we also propose an iterative semi-coherent detection that does not require any overhead to estimate the channel-state-information (CSI) while its performance can approach that of the ideal coherent detection. Simulation and analytical results show very large power gains, or coverage extension, provided by the use of multiple antennas for all the detection schemes considered.