Layered Group-Based Chirp Spread Spectrum Modulation: Waveform Design and Performance Analysis

In recent years, long-range (LoRa) has become one of the most prominent low-power wide-area network (LPWAN) technologies for the Internet of Things (IoT), which is based on a proprietary chirp spread spectrum (CSS) modulation (i.e., LoRa modulation). However, with the ever-increasing transmission demands of various IoT applications, the low-data-rate issue of LoRa modulation has become a critical bottleneck for its extensive deployment. To address this issue, we first formulate a unified framework for CSS-based waveform design and propose a novel layered group-based CSS (LGCSS) modulation scheme to achieve much higher spectral efficiency (SE) and data rate, thus accommodating a wider range of IoT applications. The complete transmitter architecture of LGCSS modulation is presented along with both coherent and non-coherent detection methods. Moreover, a comprehensive performance analysis of our proposed scheme is conducted in terms of orthogonality, bit error probability (BEP), and computational complexity. Extensive numerical simulations are conducted to verify the effectiveness of our theoretical analysis and the superiority of our proposed scheme compared to the traditional counterparts.