In this letter, we propose dual-mode chirp spread spectrum (DM-CSS) modulation for low-power wide-area networks. DM-CSS is capable of achieving a higher spectral efficiency (SE) relative to its counterparts, such as Long Range (LoRa) modulation. Considering the same symbol period, the SE in DM-CSS are augmented by: (i) simultaneously multiplexing even and odd chirp signals; (ii) using phase shifts of 0 and $\pi $ radians for both even and odd chirp signals; and (iii) using either up-chirp or down-chirp signal. The SE increases by up to 116.66% for the same bandwidth and spreading factor relative to LoRa. We present a complete transceiver architecture along with non-coherent detection process. Simulation results reveal that DM-CSS is not only more spectral efficient but also more energy efficient than most classical counterparts. It is also demonstrated that DM-CSS is robust to phase and frequency offsets.

中文翻译：

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双模啁啾扩频调制

在这封信中，我们提出了用于低功率广域网的双模啁啾扩频 (DM-CSS) 调制。DM-CSS 能够实现相对于其对应物更高的频谱效率 (SE)，例如长距离 (LoRa) 调制。考虑到相同的符号周期，DM-CSS 中的 SE 通过以下方式增强： (i) 同时复用偶数和奇数啁啾信号；(ii) 使用 0 的相移和 $\pi $偶数和奇数啁啾信号的弧度；(iii) 使用向上啁啾或向下啁啾信号。对于相同的带宽和扩频因子，相对于 LoRa，SE 最多增加 116.66%。我们提出了一个完整的收发器架构以及非相干检测过程。仿真结果表明，DM-CSS 不仅频谱效率更高，而且比大多数经典对应物更节能。还证明了 DM-CSS 对相位和频率偏移具有鲁棒性。