Comparative Analysis of Multiple Access Techniques for 6G Communication Systems

This paper provides an in-depth analysis and comparison of spectral efficiency for various multiple access (MA) techniques in operational scenarios relevant to sixth-generation (6G) communication systems, with a focus on multiple-input multiple-output (MIMO) configurations. While existing literature explores generalized channel models and operational scenarios, real-world transmission channels often exhibit significant deviations from the theoretical models typically employed. To address these limitations, we conduct a comprehensive investigation of the spectral efficiency associated with different MA strategies within proposed downlink 6G scenarios, leveraging realistic channel models. Drawing on insights from published research, we forecast essential numerical metrics and key parameters pertinent to practical 6G applications, which serve as the foundation for our analysis. The study examines contemporary non-orthogonal multiple access approaches, including power domain NOMA (PD-NOMA), sparse code multiple access (SCMA), and rate-splitting multiple access (RSMA). Numerical results for spectral efficiency are derived using MATLAB, with realistic channel matrices generated through the QuaDRiGa tool for each scenario. The findings indicate that RSMA outperforms other MA methods. While RSMA exhibits commendable performance at low antenna counts, its efficacy converges towards that of SDMA as the number of antennas increases, highlighting the practical challenges associated with achieving the targeted operational scenarios for RSMA.