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arXiv · 2507.23029

A CPFSK Transceiver with Hybrid CSS-DSSS Spreading for LPWAN PHY Communication

Wenkun Wen·Ruiqi Zhang·Peiran Wu·Tierui Min·Minghua Xia
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Abstract

Traditional low-power wide-area network (LPWAN) transceivers typically compromise data rates to achieve deep coverage. This paper presents a novel transceiver that achieves high receiver sensitivity and low computational complexity. At the transmitter, we replace the conventional direct sequence spread spectrum (DSSS) preamble with a chirp spread spectrum (CSS) preamble, consisting of a pair of down-chirp and up-chirp signals that are conjugate to each other, simplifying packet synchronization. For enhanced coverage, the payload incorporates continuous phase frequency shift keying (CPFSK) to maintain a constant envelope and phase continuity, in conjunction with DSSS to achieve a high spreading gain. At the receiver, we develop a double-peak detection method to improve synchronization and a non-coherent joint despreading and demodulation scheme that increases receiver sensitivity while maintaining simplicity in implementation. Furthermore, we optimize the preamble detection threshold and spreading sequences for maximum non-coherent receiver performance. The software-defined radio (SDR) prototype, developed using GNU Radio and USRP, along with operational snapshots, showcases its practical engineering applications. Extensive Monte Carlo simulations and field-test trials demonstrate that our transceiver outperforms traditional ones in terms of receiver sensitivity, while also being low in complexity and cost-effective for LPWAN requirements.

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Wenkun Wen, Ruiqi Zhang, Peiran Wu, Tierui Min, Minghua Xia. 2025-07-30. A CPFSK Transceiver with Hybrid CSS-DSSS Spreading for LPWAN PHY Communication. https://arxiv.org/abs/2507.23029

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