Power optimization of higher order modulated downlink non-orthogonal multiple access visible light communication

• Optimal power allocation for higher- order modulation in NOMA VLC. • The restrictions are drawn of SIC for higher-order modulation NOMA, conveying the VLC transmission to establish a threshold for discerning intended signals. • Conforming VLC’s need for real and non-negative signals, we employed unilateral M-ary pulse amplitude modulation (MPAM). • A formula is derived for optimal power allocation by maximizing throughput and obtained a solution by employing the KKT condition. • Based on above, the analysis was separated for two cases, namely, for ensured QoS and for a best-effort scenario Allocation of power is one of the critical aspects of the non-orthogonal multiple access (NOMA) system. On its implementation in higher-order modulation visible light communication (VLC), the consequent constrictions are more problematic. In this paper, power ratio was optimized for NOMA VLC with M-ary pulse amplitude modulation (MPAM). The requirements for user accessibility were chiefly derived from NOMA VLC model and applied to the throughput maximization. The power ratio for each user was then defined using the Karush–Kuhn–Tucker (KKT) optimality conditions, resulting in a suboptimal low-complexity solution for the case of QoS and optimal solution for best-effort scenario. Simulations were conducted to compare the performance between four- and eight-PAM.