Next-generation 6G communication systems are envisaged to be ultra-reliable and massive connectivity to serve multiple users with enhanced quality of service (QoS). Ramanu-jan periodic subspace division multiplexing (RPSDM)-based transform having a Toeplitz stair block diagonalize property leads to simple equalization for fading wireless environments. It results in a better approach than the orthogonal frequency-division multiplexing (OFDM)-aided systems. Conversely, conventional orthogonal multiple access (OMA) has less spectral efficiency (SE) than non-OMA (NOMA) networks that serve multiple users in the code-/time-/frequency-domain. Integrating the RPSDM modulation method with downlink NOMA networks to provide enhanced QoS with better SE while serving multiple users. Bit error rate results are provided for the aforementioned system for distinct modulation pairs, subcarrier length and power fraction allocation. Moreover, results are compared with the conventional OMA and classical OFDM-aided downlink NOMA systems. It is observed that the proposed systems outperform the conventional OFDM-NOMA systems with a gain of 8 dB SNR while increasing the FFT points. Index Terms—6G, Ramanujan periodic subspace division mul-tiplexing, non-orthogonal multiple access, orthogonal frequency-division multiplexing, successive interference cancellation.