Improving Data Confidentiality in Chirp Spread Spectrum Modulation

Chirp Spread Spectrum (CSS) modulation has shown a promising error performance especially under very low signal-to-noise ratio conditions. Thus, it has been adopted as the basic transmission scheme for Long Range (LoRa) networks which represent the most popular form of Internet of Things networks. Data are modulated in CSS by frequency chirps where the start/end frequency of the chirp implies the included transmitted data block. A main challenge in CSS systems is the vulnerability for attacks where data confidentiality can not be guaranteed. In this paper, a novel security scheme is proposed that is based on the physical-layer security principles. The proposed scheme relies on the instantaneous channel phase as a means to induce a secret frequency shift on the transmitted chirp. Analytical and simulation results show the improved data confidentiality without impacting the error performance at the legitimate receiver.