A MIMO LoRa scheme with multiple spreading factors

This paper proposes a new technique that combines Long Range (LoRa) chirp spread spectrum with multiple-input multiple-output (MIMO) antennas. The main purpose of the proposed MIMO LoRa scheme is to increase the bit rate with respect to the existing LoRa schemes. By transmitting multiple chirp waveforms with antenna-dependent spreading factor (SF), the proposed transmitting scheme achieves a bit rate more than double with respect to conventional LoRa and more than 146 percent with respect to a recently proposed MIMO LoRa scheme. This paper also proposes both coherent and noncoherent detectors for the proposed MIMO LoRa transmitting scheme. When compared with respect to conventional LoRa, the proposed transceivers show a similar computational complexity and a reduced bit error rate. When compared with respect to a recently proposed MIMO LoRa scheme, the proposed transceivers show a reduced computational complexity and a limited penalty in terms of bit error rate.