Abstract
The bit error ratio (BER) performance of a non-orthogonal multiple access (NOMA) visible light communication (VLC) system is poor due to the unequal distances between adjacent points in the superposition constellation (SC). In this paper, we propose a novel scheme to improve the BER performance by adjusting parameters to change the shape of SC at the transmitter and by adjusting the parameters of successive interference cancellation (SIC) decoding at the receiver simultaneously, which is called a SC and SIC adjustment (SC-SIC-A) scheme. For multi-user NOMA VLC system, we derive the closed-form BER expression for each user, where the modulation format is four-quadrature amplitude modulation. According to the derived BER expressions, we formulate an optimization problem that minimizes the average BER for all users by adjusting the obtained parameters of SC and SIC decoding via differential evolution algorithm. The improvement of capacity performance is investigated consequently. In order to verify the feasibility and effectiveness of the proposed SC-SIC-A scheme, we carried out theoretical analysis, Monte Carlo simulation and experiments of two-user and three-user NOMA VLC systems. Results show that the SC-SIC-A scheme outperforms the existing schemes in NOMA VLC system, where the signal-to-noise ratio (SNR) reductions to achieve BER of 10−3 are 1.3 dB and 0.8 dB for both users in the two-user NOMA VLC system, respectively, and the SNR reductions to achieve BER of 10−3 are 5.7 dB, 4.3 dB and 4.6 dB for all users in the three-user NOMA VLC system, respectively.
Highlights
As fifth generation (5G) mobile communication and the Internet of things emerge, a large number of data-intensive applications have been born, resulting in the exponential growth of data traffic [1,2]
We adjust the parameters of the superposition constellation (SC) at the transmitter and that of the successive interference cancellation (SIC) decoding at the receiver to improve the performance of the downlink multi-user non-orthogonal multiple access (NOMA) visible light communication (VLC) system without increasing the overall transmitted power of signal
We find the rule for the number of terms in each user’s bit error ratio (BER) expression, which is named as NOMA triangle regarding the terms of Q-function
Summary
As fifth generation (5G) mobile communication and the Internet of things emerge, a large number of data-intensive applications have been born, resulting in the exponential growth of data traffic [1,2]. We propose a joint transceiver optimization scheme to improve the BER and capacity performance of a multi-user NOMA VLC system using 4-QAM-OFDM. The joint transceiver optimization scheme was proposed, which is called the SC and SIC adjustment (SC-SIC-A) scheme In this scheme, we adjust the parameters of the SC at the transmitter and that of the SIC decoding at the receiver to improve the performance of the downlink multi-user NOMA VLC system without increasing the overall transmitted power of signal. In addition to BER performance, the expression of channel capacity for each user under the proposed SC-SIC-A scheme is derived. When the optimal adjustment parameters are applied to the SC-SIC-A scheme, capacity performance is improved.
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