SSK-Based PSK-LoRa Modulation for IoT Communications

LoRa has been considered as a key enabler for the next generation Internet of Things (IoT) networks. However, the low spectral efficiency (SE) of chirp spread spectrum (CSS) modulation used in LoRa is a fatal drawback for its extensive applications in the sixth generation (6G) enabled high-data-rate IoT era. In this paper, we propose SSK PSK-LoRa (slope-shift-keying and phase-shift-keying LoRa) modulation, which can achieve higher SE and better energy efficiency (EE) than the conventional LoRa modulation. In particular, the transceiver architecture of our proposed scheme is presented along with both coherent and semi-coherent detection methods. Moreover, the orthogonality of SSK PSK-LoRa symbols is analyzed and the closed-form approximations for bit error rate (BER) in both additive white Gaussian noise (AWGN) and Rayleigh fading channels are derived. Numerical results demonstrate the superiority of our proposed modulation scheme, which outperforms most classical counterparts in terms of BER and effective throughput.