Capacity analysis of index modulation multiple access system

Employing cutting-edge non-orthogonal multiple access (NOMA) techniques, index modulation multiple access (IMMA)introduces an efficient methodology. By leveraging index modulation (IM), IMMA facilitates concurrent data transmission among multiple users. It enhances this process by incorporating an additional constellation diagram that conveys extra information bits per channel utilization. In this work, we conduct a comprehensive investigation. We derive the theoretical capacity of the IMMA system and analyze mutual information across receiver channel estimation scenarios—ranging from perfect to imperfect. To validate our derivations, we execute Monte Carlo simulations, affirming our theoretical results. Notably, our findings confirm that the derived theoretical capacity formula acts as an upper bound for simulated mutual information curves. Additionally, we identify conditions for achieving the derived capacity, rigorously verifying their applicability. Through compelling comparisons, we evaluate the IMMA system's performance in mutual information and capacity against sparse code multiple access (SCMA) systems. This analysis underscores the superior attributes of the IMMA system, showcasing its potential. To illuminate practical constraints, we establish a crucial bound on users effectively sharing orthogonal resources, offering deployment insights. Furthermore, we contrast IMMA systems with traditional orthogonal multiple access (OMA) counterparts, dissecting the implications of overloading. This comprehensive approach yields a holistic comprehension of the scheme's ramifications.