In this paper we report the use of a monolithic system that combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. The device is a double pi’n/pin a-SiC:H heterostructure with optical gate connections for light triggering in different spectral regions. Results show that when a polychromatic combination of different pulsed channels impinges on the device the output signal has a strong nonlinear dependence on the light absorption profile, (wavelength, bit rate and intensity). This effect is due to the self biasing of the junctions under unbalanced light generation of carriers. Self optical bias amplification under uniform irradiation and transient conditions is achieved. An optoelectronic model based on four essential elements: a voltage supply, a monolithic double pin photodiode, optical connections for light triggering, and optical power sources for light bias explains the operation of the optical system.

Enquadramento: A rede de Cuidados de Saúde Primários deve ser a principal porta de entrada no acesso à prestação de cuidados de saúde em Portugal e um pilar fundamental do Serviço Nacional de Saúde. As alterações sociais, económicas, politicas, culturais bem como epidemiológicas conduziram a um processo de reforma, inicialmente com grande impacto nomeadamente na reestruturação da rede, com a criação de novas formas de organização, das quais se realça as Unidades de Saúde Familiares reconhecida pela avaliação da Troika. Também é verdade que nos últimos anos, esta reforma abrandou nomeadamente o ritmo inicial de implementação de USF e UCC, a visibilidade da mudança foi-se desvanecendo, deixando transparecer um desinvestimento na reestruturação dos cuidados de saúde primários Objetivo – Refletir sobre a necessidade de relançar a reforma dos Cuidados de Saúde Primários e identificar os potenciais fatores críticos de sucesso. Metodologia – Análise crítica da literatura. Resultados e conclusões – A equidade no acesso aos cuidados de saúde não está na sua totalidade assegurada e, os ganhos de eficiência organizacional não são suficientes para compensar a pressão da procura por cuidados de saúde e respetivo aumento de custos. As mudanças organizacionais implementadas alteraram as relações de cooperação interprofissional e interorganizacional, potenciando a tensão já existente entre os vários stakeholders. Novas formas organizacionais, como as Unidades Cuidados na Comunidade poderão contribuir para o equilíbrio de custos e principalmente ganhos de bem-estar para os portugueses. O relançamento da reforma da rede de cuidados de saúde primários, é imperioso na medida que pode contribuir para sustentabilidade da rede e aumentar significativamente a qualidade dos cuidados de saúde.

This study presents a novel approach to enhancing indoor navigation in crowded multi-terminal airports using visible light communication (VLC) technology. By leveraging existing luminaires as transmission points, encoded messages are conveyed through modulated light signals to provide location-specific guidance. The objectives are to facilitate navigation, optimize routes, and improve system performance through Edge/Fog integration. The methodology includes the use of tetrachromatic LED-equipped luminaires with On–Off Keying (OOK) modulation and a mesh cellular hybrid structure. Detailed airport modeling and user analysis (pedestrians and luggage/passenger carriers) equipped with PINPIN optical sensors are conducted. A VLC-specific communication protocol with coding and decoding techniques ensures reliable data transmission, while wayfinding algorithms offer real-time guidance. The results show effective data transmission and localization, enabling self-localization, travel direction inference, and route optimization. Agent-based simulations demonstrate improved traffic control, with analyses of user halting and average speed. This approach provides reliable indoor navigation independent of GPS signals, enhancing accessibility and convenience for airport users. The integration of VLC with Edge/Fog architecture ensures efficient movement through complex airport layouts.

Highlights: What are the main findings? The AI and VLC-based airport traffic management system enhances traffic flow efficiency, reduces congestion, and enhances safety through real-time asset tracking, adaptive reward mechanisms, and intelligent rerouting strategies. VLC-enabled infrastructure: Utilizes tetrachromatic LED luminaires and SiC optical receivers in a hybrid mesh network to provide precise, location-specific guidance and replace traditional gateway systems. What is the implication of the main finding? AI-driven optimization: Employs Deep Reinforcement Learning (DRL) with Q-learning to support adaptive reward allocation, dynamic phase control, and intelligent rerouting across multiple intersections. GPS-free indoor localization: Enables seamless navigation for AGVs and pedestrians through VLC-based geolocation, contributing to smoother operations, improved mobility, and an enhanced passenger experience. Airports are complex environments where efficient localization and intelligent traffic management are essential for ensuring smooth navigation and operational efficiency for both pedestrians and Autonomous Guided Vehicles (AGVs). This study presents an Artificial Intelligence (AI)-driven airport traffic management system that integrates Visible Light Communication (VLC), rerouting techniques, and adaptive reward mechanisms to optimize traffic flow, reduce congestion, and enhance safety. VLC-enabled luminaires serve as transmission points for location-specific guidance, forming a hybrid mesh network based on tetrachromatic LEDs with On-Off Keying (OOK) modulation and SiC optical receivers. AI agents, driven by Deep Reinforcement Learning (DRL), continuously analyze traffic conditions, apply adaptive rewards to improve decision-making, and dynamically reroute agents to balance traffic loads and avoid bottlenecks. Traffic states are encoded and processed through Q-learning algorithms, enabling intelligent phase activation and responsive control strategies. Simulation results confirm that the proposed system enables more balanced green time allocation, with reductions of up to 43% in vehicle-prioritized phases (e.g., Phase 1 at C1) to accommodate pedestrian flows. These adjustments lead to improved route planning, reduced halting times, and enhanced coordination between AGVs and pedestrian traffic across multiple intersections. Additionally, traffic flow responsiveness is preserved, with critical clearance phases maintaining stability or showing slight increases despite pedestrian prioritization. Simulation results confirm improved route planning, reduced halting times, and enhanced coordination between AGVs and pedestrian flows. The system also enables accurate indoor localization without relying on a Global Positioning System (GPS), supporting seamless movement and operational optimization. By combining VLC, adaptive AI models, and rerouting strategies, the proposed approach contributes to safer, more efficient, and human-centered airport mobility.

Modern airports are complex Cyber-Physical Systems (CPS), where effective coordination between physical entities – like pedestrians and Autonomous Guided Vehicles (AGVs) – and computational components is essential for safety and efficiency. This study introduces a novel CPS architecture that integrates Artificial Intelligence (AI) and Visible Light Communication (VLC) to optimize mobility and enhance real-time responsiveness. Using tetrachromatic LED luminaires modulated via On-Off Keying (OOK) and amorphous SiC optical receivers in a mesh-based hybrid topology, the system creates a VLC infrastructure that delivers real-time, location-aware navigation. A custom protocol ensures low-latency, reliable data exchange between agents and the digital core. VLC receivers capture continuous data on agent positions and movements, which is processed by Deep Reinforcement Learning (DRL) agents trained via Q-learning. These agents adaptively manage traffic flow, minimize congestion, and improve throughput. Simulations and experiments confirm the system’s advantages over traditional methods, enabling GPS-independent indoor navigation, efficient mixed traffic coordination, and scalable deployment within smart airport environments.

This paper investigates the applicability of an intuitive wayfinding system in complex buildings using Visible Light Communication (VLC). Typical scenarios include finding places. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used providing a different data channel for each chip. At the receiver, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by SiC photodetector with light filtering and demultiplexing properties. Each luminaire for downlink transmission become a single cell, in which the optical access point (AP) is located in the ceiling and the mobile users are scattered within the overlap discs of each cells underneath. The light signals emitted by the LEDs are interpreted directly by the receivers of the users underneath. The effect of the location of the APs is evaluated and a model for the cellular networks is analyzed using orthogonal topologies. A 3D localization design, demonstrated by a prototype implementation, is presented. Uplink transmission is also implemented and the 3D best route to navigate calculated. The results showed that the system allows to determine the position of a mobile target inside the network, to infer the travel direction along the time and to interact with information received optimizing the route towards the destination.

In this paper we demonstrate an add/drop filter based on SiC technology. Tailoring of the channel bandwidth and wavelength is experimentally demonstrated. The concept is extended to implement a 1 by 4 wavelength division multiplexer with channel separation in the visible range. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si: H)-n heterostructure. Several monochromatic pulsed lights, separately or in a polychromatic mixture illuminated the device. Independent tuning of each channel is performed by steady state violet bias superimposed either from the front and back sides. Results show that, front background enhances the light-to-dark sensitivity of the long and medium wavelength channels and quench strongly the others. Back violet background has the opposite behaviour. This nonlinearity provides the possibility for selective removal or addition of wavelengths. An optoelectronic model is presented and explains the light filtering properties of the add/drop filter, under different optical bias conditions.

We investigate the applicability of an intuitive advertising system for large indoor environments using visible light communication (VLC). This VLC-based positioning system includes the use of the visible light signals to light the space and to transmit information for traveler positioning and for advertising campaigns in the surroundings. As transmitters, white RGB-LEDs were used. Although their original function is to provide illumination, due to the ability of each individual chip to switch quickly enough to transfer data, they were used to broadcast information. This functionality is used for communication where multiplexed data can be encoded in the emitting light. The light signals emitted by the LEDs, positioned in the area of an advertising campaign are interpreted directly by the customers’ receivers. A silicon carbide optical sensor with light filtering and demultiplexing properties receives the modulated signals containing the ID, the geographical position of the LED, and other information, and then it demultiplexes and decodes the data and locates the mobile device within the environment. Different layouts are analyzed; square and hexagonal meshes are tested, and a two-dimensional localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. For both, the transmitted information, indoor position, and motion direction of the customer are determined. The results show that the LED-aided VLC navigation system enables to determine the position of a mobile target inside the network, to infer the travel direction as a function of time, and to interact with the received information.

To support people’s wayfinding activities in unfamiliar indoor environments, a method able to generate ceiling landmark route instructions using Visible Light Communication (VLC) is proposed. The system is composed of several transmitters (ceiling luminaries) which send the map information and path messages required to wayfinding. Mobile optical receivers, using joint transmission, extracts theirs location to perform positioning and, concomitantly, the transmitted data from each transmitter. Bidirectional communication between the emitters and the receivers is available in strategic optical access point. Typical scenarios are simulated and include finding places and guiding users across different floors. Data from the sender is encoded, modulated and converted into light signals emitted by the transmitters. Tetra-chromatic white sources are used, providing a different data channel for each chip. At the receiver, the modulated light signal, containing the ID and the 3D geographical position of the transmitter and wayfinding information, is received by SiC photodetectors with light filtering and demultiplexing properties. Since lighting and wireless data communication is combined, each luminaire for downlink transmission become a single cell, in which the optical access point (AP) is located. The coded light signals are interpreted directly by the receivers of the users positioned underneath. The effect of the location of the APs is evaluated and a model for the different cellular networks is analyzed. Orthogonal and hexagonal topologies are tested, and a 3D localization design, demonstrated by a prototype is presented. Uplink transmission is implemented and the 3D best route to navigate through venue calculated. The results show that the system make possible to determine the position of a mobile target inside the network, to infer the travel direction along the time and to interact with information received and optimize the route towards a static or dynamic destination.

A LED-assisted navigation system for large indoor environments is proposed. White LEDs are used both for illumination purposes and as transmitters. On-off keying modulation scheme is used to broadcast the information together with the identifiers, IDs, related to the physical location of the transmitters. The mobile receiver is implemented using a double p-i-n/pin SiC photodetector with light controlled filtering properties. Coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel are analysed. Fine-grained indoor localization is demonstrated. Different indoor layouts, using as position technique a four-code assignment for the LEDs, are proposed. Square and hexagon mesh are tested, and a 2D localization design, demonstrated by a prototype implementation, is presented. The key differences between both topologies are discussed. The location and motion information is calculated by position mapping and estimating the location areas along the time. In both topologies, the transmitted data information, indoor position and motion direction of the mobile device are determined. The results showed that the LED-aided VLC navigation system make possible not only to determine the position of a mobile target inside the unit cell but also in the network and concomitantly to infer the travel direction along the time.