No abstract

In order to overcome the limitation of narrow modulation bandwidth on the performance in the visible light communication (VLC) systems, non-orthogonal multiple access (NOMA) is applied to the downlink VLC networks in this paper to improve the sum rate performance effectively. We first propose an optimal power allocation strategy which is based on the multi-factor control (MFOPA), aiming to maximize the total system capacity subject to ensuring all users' quality of service (Qos) and fairness, as well as illumination requirements. The analytical results indicate that the proposed MFOPA could provide higher system sum rate and better user fairness as well as guarantee the Qos and eye safety of each user at the same time when compared with the static power allocation (SPA) and gain ratio power allocation (GRPA) schemes, especially in high demand for signal-to-interference-plus-noise ratio (SINR). What is more, considering the residual interference may exist during the successive interference cancellation (SIC) at the receiver, namely imperfect SIC, the interference cancellation factor is also taken into account in MFOPA strategy. The numerical results are shown to demonstrate the robustness and effectiveness of the MFOPA in NOMA-VLC when the residual interference remains. INDEX TERMS Visible light communication (VLC), non-orthogonal multiple access (NOMA), power allocation, multiple factors, imperfect successive interference cancellation (SIC).

Recently, due to its higher spectral efficiency and enhanced user experience, non-orthogonal multiple access (NOMA) has been widely studied in visible light communication (VLC) systems. As a main concern in NOMA-VLC systems, the power allocation scheme greatly affects the tradeoff between the total achievable data rate and user fairness. In this context, our main aim in this work was to find a more balanced power allocation scheme. To this end, an adaptive power allocation scheme based on multi-attribute decision making (MADM), which flexibly chooses between conventional power allocation or inverse power allocation (IPA) and the optimal power allocation factor, has been proposed. The concept of IPA is put forward for the first time and proves to be beneficial to achieving a higher total achievable data rate at the cost of user fairness. Moreover, considering users’ mobility along certain trajectories, we derived a fitting model of the optimal power allocation factor. The feasibility of the proposed adaptive scheme was verified through simulation and the fitting model was approximated to be the sum of three Gaussian functions.

This paper investigates a downlink power allocation scheme for application of non-orthogonal multiple access (NOMA) in visible light communication (VLC) systems. Aiming to achieve a flexible tradeoff between sum rate and user fairness depending on administrators’ subjective setting and acquire the optimal solution for any setting, we formulate two optimization problems, which are closely aligned with the practical application. Specifically, one is user fairness-guaranteed sum rate maximization, the other is sum rate-guaranteed user fairness maximization. Moreover, through classified discussion around the threshold guaranteeing user fairness or sum rate, we present rigorous mathematical derivation and optimization analysis, and two corresponding algorithms are proposed. Furthermore, through numerical simulation, the superiority of our proposed algorithms over conventional schemes is verified in terms of meeting the practical demand and performance gain in sum rate, user fairness, and coverage probability.

Recently, the demand for high data traffic transmission is experiencing unstoppable growth, and multi-beam high-throughput satellite (HTS) systems have proven to be effective solutions. However, how to manage and eliminate the co-channel interference caused by frequency reuse in multi-beam HTS systems is still a challenging issue. Motivated by this background, this paper begins with discussing the interference mechanism in the uplink and downlink of HTS systems and then uses the quantification method of carrier-to-interference ratio (CIR), whereby the influencing factors of the CIR are accordingly analyzed. In addition, the common CIR selection strategies are summarized and compared with each other in terms of their advantages and disadvantages. Based on the proposed CIR quantification and statistical selection methods, two frequency plan cases are simulated for the scenario of 19 beams with 4-color reuse. The results show that the proposed quantification and selection methods are rather practical and offer a feasible approach for frequency plan adjustment based on CIR optimization. Finally, a simulation analysis of the CIR under different power spectral density (PSD) values is conducted, and the results show that the PSD has a substantial impact on the CIR.