As 6G and beyond aim for sustainable, high-capacity wireless connectivity, optical wireless communication (OWC) has emerged as a compelling solution. Recent advances in vertical-cavity surface-emitting laser (VCSEL) arrays have significantly enhanced OWC performance, enabling high-speed, low-power data transmission. However, dense VCSEL deployments introduce challenges related to interference and energy efficiency (EE). This paper proposes a scalable precoding framework for EE maximization in fully cooperative VCSEL-based OWC broadcast systems. We formulate a non-convex optimization problem to design the precoding matrix under practical optical constraints while guaranteeing minimum user rates. To solve this, we apply Dinkelbach’s method to handle the fractional objective and the inner approximation technique to iteratively convexify and solve the problem. Simulation results show that our approach consistently outperforms regularized zero-forcing in terms of EE, particularly in large-scale deployments, demonstrating its potential for next-generation sustainable dense OWC networks.

Visible Light Positioning (VLP) systems present a promising alternative for indoor positioning by leveraging existing Light-Emitting Diode (LED) lighting infrastructure to achieve high accuracy. However, challenges such as uneven error distribution and vulnerability to transmitter failures can compromise system robustness. This study conducts a comprehensive comparative analysis of machine learning estimators for VLP, emphasizing spatial segmentation and transmitter failure scenarios. An experimental setup with four LED transmitters was utilized to collect a dataset of received signal strengths across various positions within a$1.2 \times 1.2 \mathrm{m}$testbed. Polynomial interpolation was applied to augment the dataset, expanding the number of samples from 169 to 625. The workspace was divided into center and edge regions based on cumulative angles of emission, and classification models were employed to validate this segmentation. Several machine learning estimators were evaluated for position estimation. Gaussian Process (GP) regressor achieved the lowest overall Root Mean Square Error (RMSE) of 1.973 cm, particularly excelling in the center region. All models exhibited lower errors in the center compared to the edge, highlighting significant regional disparities. Robustness under transmitter failure was assessed by simulating the failure of one transmitter. GP regressor demonstrated resilience, maintaining low RMSE and experiencing moderate performance degradation (28.1 %). These findings underscore the importance of spatial segmentation in VLP systems and the effectiveness of GP and Support Vector Machine estimators in achieving robust and accurate positioning. The study suggests that accounting for regional differences and potential transmitter failures can lead to more resilient and precise VLP solutions.

Optical wireless communication (OWC) is now seen as a serious complement to radio frequency solutions, as the latter may soon face a spectrum crunch. OWC systems, however, usually rely on cells generated by fixed access points, so that they often experience a strong quality of service degradation because of frequent handover and inter-cell interference. To overcome these problems, steerable optical antennas may be used at both the infrastructure and user levels. Although such beamsteering solutions have already been explored experimentally, there seems to be no thorough comparison of the performance of such a system, especially in terms of coverage, compared to conventional solutions based on fixed antennas. This paper thus aims to provide such a comparison by simulating three scenarios (‘with beamsteering’, ‘without beamsteering’, and with ‘manual orientation’), for each of which the bit error rate of a multiband carrierless amplitude phase modulation signal received by a user moving across a$20\times 20 \ \mathbf{m}$receiving plane at 0.85 m from the floor is estimated. The parameters of this source, its directivity and emission optical power, in particular, are carefully chosen to meet photobiological regulations, and their influence on the coverage is also studied. The results obtained show that beamsteering still enables, in the worst case, a threefold increase in coverage compared to scenarios where it is not or partially used.

Although optical wireless communication (OWC) is seen as a promising complementary technology to radio frequency systems, its deployment is currently hampered by its limited communication range and the lack of compactness of its transceivers. A partial solution lies in using more sensitive photoreceivers, such as arrays of single photon avalanche diodes (SPAD). Despite their limited bandwidth and non-linearity, such devices have been shown to support Gbps data transmission while providing greatly enhanced sensitivity compared to conventional photodiodes (PD). However, their potential to increase the communication coverage of an indoor OWC system has never been studied. In this paper, a simulation framework for evaluating this metric using a SPAD-based indoor OWC system is thus detailed and implemented. Results show that an array of SPADs in the order of a mm2is enough to ensure connectivity over a whole 16 m2room, whereas similar performance with a PD requires a sensitive area of several hundreds of mm2, hence demonstrating the interest of SPADs for coverage as well as compactness optimization in OWC.

This paper considers the use of infrared-based optical wireless communications for multi-user uplink wireless body-area networks. We propose the use of optical-orthogonal frequency division multiple access (O-OFDMA) signaling to manage the multiple access (MA) requirement for relatively high-rate medical applications. In particular, we consider asymmetrically clipped O-OFDMA and analyze its performance in terms of bit-error-rate and outage probability in the presence of multi-user time synchronization errors. These latter may occur due to mobility and random transmitter orientations, and will impact the link performance by inducing MA interference (MAI). We show that the effect of MAI increases with increasing the data rate. For instance, for 1 and 2 Mbps data rates, to achieve a target bit-error-rate of 10−3, the link distance is limited to 1.9 and 1 m, respectively, compared to 2.2 and 1.8 m in the absence of MAI.