Optimum Power Allocation of NOMA/DCO-OFDM for VLC Systems

Future wireless networks are anticipated to use the highly efficient technique known as non-orthogonal multiple access (NOMA) but at the expense of more data detection error. The common O-OFDM scheme has been achieved is DC-biased optical OFDM (DCO-OFDM). In the current study a NOMA/DCO-OFDM model with two scenarios is proposed: two-user and three-user scenarios with different modulation order of a square quadrature amplitude modulation (QAM). To guarantee that there are no overlaps or crossings between the symbols in the superposed constellation, an optimal power allocation (PA) is derived for user 2 in the first scenario and the users 2 and 3 in the other scenario. In terms of BER, the outcomes show that the BER of the first user in the two scenarios decreases as the power allocated is increased. Additionally, the results depict that, under the derived optimal PA, the second user in the first scenario and the second and third users in the second scenario have lower BER and hence better performance. As well as the worst case of PA conditions is obtained and verified through simulation.