Hitting the Sweet Spot: An SF-any Coding Paradigm for Empowering City-Wide LoRa Communications

LoRa technology has garnered significant attention for its exceptional performance in city-wide applications. LoRa encodes data across multiple samples to enable long-range communication, with the level of redundancy controlled by the Spreading Factor (SF). However, practical limitations restrict how high the SF can be set. To overcome communication challenges at the highest allowable SF settings, we introduce SF-any, a software-based coding paradigm that extends an SFk packet to a quasi-SF(k + m) packet. SF-any encodes a quasi-SF(k + m) symbol with 2
^m
SFk symbols. Hardware imperfections introduce time-varying frequency drifts and phase offsets, resulting in frequency leakage during quasi-SF(k +m) packet decoding. To mitigate this, we strategically insert pilots into the packet for imperfection estimation and compensation. Additionally, to maintain and exploit the coding structure in LoRa PHY, we employ a grouped repetition code at the transmitter and a joint demodulation and decoding scheme at the receiver. Comprehensive evaluations demonstrate that SF-any’s performance seamlessly scales with increasing SF, achieving up to a 14dB improvement over SF12 packets (the highest SF in LoRa PHY), and up to a 12dB improvement compared with state-of-the-art approaches.