This paper outlines the concept of a multilevel bipolar on-off keying hybrid optical wireless communication (OWC) system using a single light-emitting diode (LED) as a transmitter as well as photodiode and camera-based receivers for versatile indoor Internet of Things applications. The proposed system offers simultaneous high- and low-speed transmission capabilities using visible light communication (VLC) and optical camera communication (OCC) links, respectively. By means of experimental implementation, we show that the hybrid OWC system employing a chip LED modulated with a multilevel signal improves the data rate Rb as well as the bit error rate and reception success rate of VLC and OCC links, respectively, by doubling the bandwidth. We show that the proposed scheme can provide an independent link performance, irrespective of significant differences between the operating Rb of VLC and OCC over a range of transmission spans L. We demonstrate that the throughput of the VLC link is improved by up to ~100 Mb/s, which corresponds to twice the LED bandwidth, using direct modulation, different amplitude levels, and optimizing the received optical power of the hybrid OWC link. Error-free data transmission for the OCC link is achieved for all values of Rb, amplitude overlap of 0 and 0.3, and a range of L.

Wearable communication is one of the key drivers in the Internet of Things (IoT) and body area networks for transmitting vital sensory data. Wearable devices must be lightweight, flexible, and have low energy consumption. In this context, optical wireless communication offers several significant advantages, such as immunity to the radio frequency-induced electromagnetic interference, broad unlicensed spectrum, and enhanced physical layer security. Wearable devices employing light-emitting diodes coupled to side-emitting optical fibers form energy-efficient, lightweight, flexible, and omnidirectional distributed optical transmitters, which are ideal for IoT applications. In this paper, we propose an optical camera communication (OCC)–based wearable system with a unique image processing algorithm capable of detecting and recovering data from distributed transmitters of arbitrary shapes. Experimental results demonstrate the feasibility of the proposed system, where for distances up to 4 m, the bit error rate (BER) performance is well below the forward error correction BER limit with values as low as ${5.5} {\times }\text {10}^{ {-}\text {5}}$. The presented results demonstrate the potential of OCC-based systems using side-emitting fibers for IoT applications.

The use of quantum key distribution (QKD) to improve security may impact the quality of service (Qos) of high rate classical data links. The key generation process with an empty buffer can be modeled as a queuing system, and data throughput limits can be determined using queueing theory to assess the impact on the QoS. The proposed key generation model is based on an on-demand paradigm. Based on the results of this study, a discrete variable (DV)-QKD-secured link could be designed using the data rate bounds to guarantee a given QoS. Furthermore, we validate the derived bounds by comparing the theoretical derivations with simulations. We show that in a one-time-pad system, the achievable throughput approaches 0.59 times the secret key rate as the key length increases. In the case of a key scheme with key reuse, the throughput is asymptotically linear with the number of key reuses, and the slope of the curve corresponds to the secret key rate multiplied by a function of the protocol and channel characteristics. The analysis is carried out on optical fiber and free-space links.

We present a distributed receiver for visible light communication based on a side-emitting optical fiber. We show that 500 kbps data rate can be captured with a bit-error rate below the forward-error correction limit of 3.8·10⁻³ with a light-emitting diode (LED) transmitter 25 cm away from the fiber, whereas by increasing the photodetector gain and reducing the data rate down to 50 kbps, we improve the LED-fiber distance significantly up to 4 m. Our results lead to a low-cost distributed visible-light receiver with a 360° field of view for indoor low-data rate, Internet of Things, and sensory networks.

This letter proposes a novel dual-layer security framework for visible light communication (VLC) by integrating the BB84 quantum key distribution (QKD) protocol with beam directivity-based physical layer security (PLS). This combined approach enhances resilience against eavesdropping threats, offering stronger security compared to individual techniques, particularly in highly secure environments. The analysis indicates that in the first layer, simulated in $\mathrm{MATLAB}^{\circledR} $ , the QKD system with multiphoton source benefits from an increased average number of photons, improving the secret key fraction and enhancing resistance to quantum channel attenuation. However, this advantage comes at the expense of heightened vulnerability to photon number splitting (PNS) attacks. To mitigate this, the second layer, location-based PLS, which is implemented on an experimental testbed, restricts Eve’s access to the VLC data channel by leveraging beam directivity. Within the limitations defined by the controlled indoor setup, the obtained results demonstrate that even under a strong PNS attack, Eve’s best bit error rate (BER) remains higher at $2.4\times 10 ^{\mathbf {-2}}$ compared to Bob’s worst BER at $3.7\times 10 ^{\mathbf {-3}}$ , ensuring secure communication.

In this work, a new Time Difference of Arrival (TDoA) scheme for distance measurement based on Optical Camera Communication (OCC) systems is proposed. It relies on the use of optical pulses instead of radio-frequency signals as the time reference triggers, and the introduction of a rolling shutter camera, whose characteristics allows substituting the timer modules used in conventional TDoA techniques by image processing of the illuminated area in the picture. This processing on the camera’s images provides time measurements and implies and specific analysis, which is presented in this work. The system performance and properties, such as resolution and range, mainly depends on the camera characteristics, such as the frames capture rate and the image quality. This new technique is suitable to be implemented in smartphones or other Commercial Off-The-Shelf (COTS) devices equipped with a camera and speakers.