Variable Rate Non-Binary Coded Schemes Based on PSK-LoRa Modulation and LDPC Codes

We investigate PSK-LoRa modulation, which serves as an alternative to LoRa by introducing additional information in the phase using Phase-Shift Keying (PSK) symbols. This extension of LoRa provides flexibility in achieving spectral efficiency gains while maintaining a constant envelope. To fully leverage the advantages of PSK-LoRa, we propose a variable nonbinary coded scheme that allows for varying the proportion of bits associated with LoRa modulation and PSK modulation, while maintaining a fixed number of bits per PSK-LoRa symbol. This approach enables coverage of a wide range of spectral efficiencies using a single outer error-correcting code for all inner modulation schemes. We demonstrate that regular non-binary LDPC (Low- Density Parity-Check) codes are highly effective for our scheme based on PSK-LoRa for the Gaussian channel. However, due to a lack of diversity offered by the receiver, the performance of these codes are significantly penalized for the Rayleigh channel. Hence, we investigate quasi-regular, precoded punctured, and irregular codes for the Rayleigh channel. We illustrate that irregular nonbinary LDPC codes emerge as strong candidates for both the Gaussian and Rayleigh channels.