DeRa: Deep-Range Low-Power Wide Area IoT via Ultra-sensitive Signal Detection

Abstract

LoRa extends communication range by operating well below the noise floor, yet this capability hinges on reliable packet detection—an overlooked bottleneck. Carrier frequency offset (CFO) introduces deterministic inter-chirp phase shifts that prevent coherent preamble accumulation; because all existing detectors fall back on non-coherent, magnitude-only addition, they forfeit substantial signal power. We present DeRa, a phase-coherent LoRa detection and decoding framework built on three contributions: (1) a phase-coherent detection method that exploits the relationship between CFO and inter-chirp phase evolution to detect weak packets; (2) analytical compensation of compound CFO-induced scaling distortions—timing drift, frequency migration, and energy leakage—so that coherent accumulation remains effective even under 40 kHz CFO, eliminating the need for expensive oscillator hardware; and (3) a CRC-guided, phase-compensated iterative decoder that coherently recombines split symbol energy and closes the detection-to-decoding feedback loop. On COTS LoRa devices across SF 7–12, DeRa lowers the detection threshold by 4.3–4.8 dB and the decoding threshold by 3.3–3.9 dB over state-of-the-art baselines, while maintaining O(N log N) per-symbol complexity and consistent gains in real-world field experiments.