LoRa Throughput Analysis with Imperfect Spreading Factor Orthogonality

TL;DR

This paper provides a theoretical analysis of LoRa uplink throughput considering imperfect Spreading Factor orthogonality, revealing throughput losses and aiding the design of better SF allocation strategies for IoT networks.

Contribution

It introduces a novel theoretical model that accounts for non-ideal SF orthogonality in LoRa, which was previously assumed perfect, to better predict throughput performance.

Findings

Throughput decreases due to imperfect SF orthogonality.

The analysis accurately predicts throughput losses under various SF allocations.

Results facilitate the design of improved SF allocation mechanisms.

Abstract

LoRa is one of the promising techniques for enabling Low Power Wide Area Networks (LPWANs) for future Internet-of-Things (IoT) devices. Although LoRa allows flexible adaptations of coverage and data rates, it is subject to intrinsic types of interferences: co-SF interferences where end-devices with the same Spreading Factors (SFs) are subject to collisions, and inter-SF interferences where end-devices with different SFs experience collisions. Most current works have considered perfect orthogonality among different SFs. In this work, we provide a theoretical analysis of the achievable LoRa throughput in uplink, where the capture conditions specific to LoRa are included. Results show the accuracy of our analysis despite approximations, and the throughput losses from imperfect SF orthogonality, under different SF allocations. Our analysis will enable the design of specific SF allocation mechanisms, in view of further throughput enhancements.