Time Domain Multiplexed LoRa Modulation Waveform Design for IoT Communication

Long-Range (LoRa) is one of the emerging technologies in low-power wide-area networks (LPWANs). In this letter, we proposed a Time Domain Multiplexed LoRa (TDM-LoRa) modulation to improve the throughput of conventional LoRa by using up-chirp and down-chirp simultaneously. A low complexity non-coherent algorithm for the TDM-LoRa modulation is also presented. We then derive an analytical expression for the bit error rate (BER) of non-coherent demodulation in the additive white Gaussian noise (AWGN) channel. In addition, a scheme that encodes information bits on both in-phase and quadrature components of the TDM-LoRa symbol is presented to further improve the system data rate. Performance analysis and simulation show that our proposed schemes can achieve better spectral efficiency (SE) and throughput without obvious bit error rate (BER) degradation compared to the LoRa Physical Layer (PHY) scheme.