MIMO-OCDM-NOMA: Enhancing Spectral Efficiency and Robustness in High-Mobility, Interference-Prone Environments

This paper presents the integration of Orthogonal Chirp Division Multiplexing (OCDM) and Non-Orthogonal Multiple Access (NOMA) within a Multiple-Input Multiple-Output (MIMO) framework, referred to as MIMO-OCDM-NOMA, to address the limitations of conventional multicarrier systems in high-mobility and interference-prone environments. The proposed MIMO-OCDM-NOMA framework enhances spectral efficiency by leveraging the power domain multiplexing of NOMA. The use of chirp signals in OCDM improves bit error rate (BER) performance, owing to their inherent robustness against noise, multi-path fading, and interference. The analysis explores the effects of imperfect successive interference cancellation (SIC), revealing that the chirp-based modulation in OCDM successfully reduces residual interference, thereby enhancing the system's overall robustness. The simulation results demonstrate that the proposed MIMO-OCDM-NOMA system efficiently mitigates channel interference and sustains high spectral efficiency, even under the conditions of imperfect SIC.