The user-centric (UC) association in optical wireless communication (OWC) forms amorphous cells (A-Cells) by considering the dynamic distribution and load demand of user equipments (UEs). This philosophy offers advantages over the conventional network-centric (NC) association that purely relies on a pre-defined and fixed network configuration, in terms of alleviating undesired inter-cell interference (ICI) and achieving superior system performance. However, constructing the optimal A-Cells for a given OWC network, including determining the appropriate number of A-Cells associated to their contained UEs, is deeply integrated with the UEs’ distribution and transmission conditions. To address the intractable issue, in this paper, we conceive an adaptive UC-OWC network that relies on a feedback-guided iterative framework, which is capable of jointly optimizing A-Cells formation, modulation-mode assignment and power allocation strategies. For the sake of attaining the optimized throughput of this adaptive network, we initialize the UC association by the designed k-means based genetic algorithm (KGA), which can then be iteratively adjusted based on the throughput feedback obtained via our proposed multi-user cross Q-learning (MUCQ) resource allocation algorithm. Simulation results indicate that, compared to conventional counterparts, our adaptive UC-OWC network is able to significantly improve throughput performance and reduce outage probability.

Visible light communications (VLC) constitutes as a promising downlink technique of supporting the ever-increasing tele-traffic. Since the ubiquitous mains power line constitutes a natural backbone feed for VLC, a combined power line and VLC network is conceived, where the source data is fed by power line communications (PLC) into the VLC network. We refer to it as a PLC-VLC network, where the power-line connects the light emitting diodes (LED) without requiring a duplicated filter-backbone. Then the information is forwarded to multiple users via visible light. Furthermore, to increase the downlink bit rate, non-orthogonal multiple access (NOMA) is invoked in VLC. For the sake of maximizing the sum-throughput, we conceive a joint PLC-VLC power allocation (JPA) strategy. Our simulations demonstrate that NOMA significantly outperforms orthogonal multiple access (OMA) with the aid of the proposed JPA.

Capable of supporting the dual functionalities of dimming control and high-speed data transmission, dimmable optical orthogonal frequency division multiplexing (O-OFDM) has attracted increasing attentions in visible light communication (VLC). A major design challenge in the dimmable O-OFDM is to realize spectrally efficient VLC link compatible with dimming control while conforming to the low-complexity philosophy of the intensity modulation/direct detection (IM/DD) system. To cope with this challenge, a novel scheme is conceived, named as adaptively biased layered O-OFDM (ABLO-OFDM), which can be well integrated with the industry-preferred pulse width modulation (PWM) dimming technique. Similar to the conventional layered asymmetrically clipped O-OFDM (LACO-OFDM), multiple layers of subcarriers are utilized to transmit information data in ABLO-OFDM, resulting in high spectral efficiency. Only one inverse fast Fourier transform (IFFT) block is required in ABLO-OFDM to generate the layered O-OFDM signal compared to multiple IFFT blocks in LACO-OFDM. Moreover, the demodulation of the dimmable ABLO-OFDM (DABLO-OFDM) signal can straightforwardly rely on standard OFDM receiver, which is immune to the dimming process. Therefore, the proposed scheme achieves high spectral efficiency whilst possessing low-complexity transceiver compared to conventional O-OFDM. It is shown that DABLO-OFDM is superior to its counterparts in terms of the achievable spectral efficiency for intermediate dimming levels.

The concept of amorphous-boundary-based user-centric cells invoked for visible light communication (VLC) was shown to offer extra throughput benefits over the conventional network-centric VLC. However, this improvement was quantified based on a number of idealized simplifying assumptions, such as operating exactly at the Shannon capacity. Also, the light emitting diode in VLC was assumed to have no non-linear distortion and no clipping distortion. Furthermore, greedily supporting all the user equipments in the system may in fact reduce the achievable throughput, when the transmit power is restricted. To provide more practical performance estimate, in this paper, the dynamic throughput maximization of user-centric VLC (UC-VLC) systems is investigated under a range of practical considerations, where the number of served UEs, the modulation-mode assignment and the power allocation strategy are all dynamically decided by our proposed heuristic dynamic-programming-based algorithm. Our simulations indicate that both the achievable throughput and the outage probability of the proposed UC-VLC system is better than that of the conventional NC-VLC system, under a range of practical constraints.

In optical wireless communication (OWC), conventional superimposed optical orthogonal frequency division multiplexing (OOFDM) techniques, such as hybrid asymmetrically clipped OOFDM (HACO-OFDM), require an additional operation of interference cancellation to decode transmitted symbols, which leads to relatively high receiver complexity with processing delay. In this paper, we propose a novel superimposed OOFDM scheme with low-complexity receiver, named as interference-free hybrid OOFDM (IFHO-OFDM), for OWC. In the proposed IFHO-OFDM, two hybrid OOFDM components are combined for simultaneous transmission to achieve the appealing advantages of high spectral efficiency, and a time-selective bias is designed to guarantee the non-negativity while maintaining high power efficiency. Moreover, we propose to superimpose the two hybrid OOFDM components in an interference-free way, and thus, it can be readily demodulated by a standard low-complexity OFDM receiver. Simulation results verified the superiority of the proposed IFHO-OFDM in terms of both peak-to-average-power ratio (PAPR) and bit error rate (BER) compared to HACO-OFDM.