Abstract
We characterize the LoRa channel in terms of multi-path fading, loss burstiness, and assess the benefits of Forward Error Correction as well as the influence of frame length. We make these observations by synthesizing extensive experimental measurements realized with The Things Network in a medium size city. We then propose to optimize the LoRaWAN Adaptive Data Rate algorithm based on this refined LoRa channel characterization and taking into account the LoRaWAN inherent macro-diversity from multi-gateway reception. Firstly, we propose ADRopt, which adjusts Spreading Factor and frame repetition number to maintain the communication below a target Packet Error Rate ceiling with optimized Time-On-Air. Secondly, we propose ADRIFECC, an extension of ADRopt in case an Inter-Frame Erasure Correction Code is available. The resulting protocol provides very high reliability even over low quality channels, with comparable Time on Air and similar downlink usage as the currently deployed mechanism. Simulations corroborate the analysis, both over a synthetic random wireless link and over replayed real-world packet transmission traces.
Highlights
The growth of the Internet of Things (IoT) brings legacy wireless networks technologies to their limits
We establish a channel model which reflects the observations we make after generating and analyzing traffic collected on a real-word LoRaWAN deployment
The channel model includes the distribution of the received power around its average, the erasure patterns, and the influence on the demodulation floor of the frame length, as well as of LoRa Forward Error Correction
Summary
The growth of the Internet of Things (IoT) brings legacy wireless networks technologies to their limits. The scalability, energy consumption and cost of conventional cellular technologies makes them unsuitable for the massive deployments required in the contexts of the smart city, smart farm, smart factory, wide scale asset tracking, and so forth To address these challenges, Low Power Wide Area Networks (LPWAN) promise to provide long range and large scale connectivity for the IoT, at low cost and low power consumption. LoRaWAN claims the ability to provides connectivity to thousands of battery-powered autonomous End-Devices (EDs) within ten kilometers of a single gateway (GW) with throughput up to a kilobyte per second, for a decade These performances attract the interest of both the academic community and the industry, and put LoRaWAN at the forefront among LPWAN technologies
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