Downlink Performance Evaluation of NOMA Systems Based on Different OFDM Waveforms

Non-orthogonal multiple access (NOMA) schemes have emerged as an inspiring technology for next generation mobile communication systems. This paper firstly confirms the superiority of NOMA systems over orthogonal multiple access (OMA) schemes by considering orthogonal frequency division modulation (OFDM) waveform. Further, it is verified that coded NOMA systems based on low-density parity-check (LDPC) coding outperform uncoded NOMA systems in terms of bit error rate (BER) performance metric with respect to transmit power. To show the performance of OMA and NOMA systems, two cells each having a single base station (BS) are constructed. For simplicity, two devices are considered in OMA cell while four devices are used in NOMA cell which utilize multiple user superposition transmission (MUST) technique (downlink power-domain version of NOMA). Later, performance of the system is analyzed in terms of throughput and peak-to-average power ratio (PAPR) for downlink scenario. Lastly, performance of the considered system for different waveforms such as OFDM, weighted over lap and add (WOLA) and filtered OFDM (F-OFDM) is compared. According to obtained simulation results, WOLA waveform generally outperforms OFDM and F-OFDM waveforms in throughput, however, slight better results are being shown by F-OFDM waveform in high PAPR values.