Performance Analysis of OMA / NOMA for VLC Communication Systems

Visible light communication (VLC) permits to utilize light-emitting diodes (LEDs) in optical wireless communication (OWC) for data transmission as well as to for illumination. Non-Orthogonal Multiple Access (NOMA) has been introduced for the next generations wireless systems to support multiple users in indoor environment. Orthogonal frequency multiple access (OFDM) is used because of its high spectral efficiency. In this paper, a hybrid NOMA/DCO-OFDM and NOMA/ACO-OFDM is proposed to enhance the performance in terms of bit error rate (BER) of two users located in the cell. Power allocation condition (PAC) is used to share the total power that transmitted from the LED between the users. The furthest user is assigned high power due to its low channel gain, while the other user is receiving low power. The BER of user 1 and user 2, as function of PAC (
$\boldsymbol{\alpha} \mathbf{1}=\mathbf{0.5}$
to 1), for different SNR values is obtained. Increasing
$\boldsymbol{\alpha} \mathbf{1}$
leads to decreasing the BER also higher SNR reduces the BER. For user 2 the optimal value of
$\boldsymbol{\alpha} \mathbf{1}$
is 0.8 which correspond the lowest BER. After that the BER will increase due to the power allocated to user 2 being lower than the optimal power. Also, the results show that NOMA/ACO-OFDM model is better than NOMA/DCO-OFDM. When user2's constellation order is altered, M2=16 while M1=4 for the two models, outcomes demonstrate that user2's BER experienced a significant influence.