Comparative Analysis of 8x8 MIMO-OFDMA and NOMA Systems 

Abstract This paper presents a comprehensive performance analysis of an 8x8 MIMO (Multiple Input Multiple Output) system using Orthogonal Frequency Division Multiple Access (OFDMA) and Non-Orthogonal Multiple Access (NOMA) techniques. The study is conducted at a carrier frequency of 1 GHz, utilizing 16-QAM modulation, an FFT size of 512, a cyclic prefix of 64 samples, and a Signal-to-Noise Ratio (SNR) range from-10 to 20 dB. Key performance metrics, including Bit Error Rate (BER), Error Vector Magnitude (EVM), and channel gain diversity, are evaluated across both multiple access schemes. Simulation results reveal the strengths and weaknesses of OFDMA and NOMA under identical conditions, highlighting how each technique impacts BER performance, EVM behaviour, and SNR gain per receive antenna. The results indicate that OFDMA consistently achieves lower BER, with a value of approximately 0.43 at 20 dB SNR, compared to NOMA's 0.86, showcasing its superior reliability in high SNR conditions. EVM results also favor OFDMA, achieving 15 dB lower EVM at 20 dB SNR, indicating better signal quality. However, NOMA demonstrates higher spectral efficiency and improved fairness between users, making it advantageous in resource-constrained scenarios. Overall, OFDMA is recommended for applications prioritizing low BER and high signal quality, while NOMA is more suitable for systems aiming to maximize user capacity and spectral efficiency.