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This study presents insights into high-speed optical wireless communication (OWC) within plastic pipes, introducing a Gbps-capable alternative for challenging environments. Utilizing a 1W LED with five wavelengths, the experiment explores signal power, attenuation, and bandwidth characteristics. Notably, the blue LED achieves an unprecedented 58.64 MHz bandwidth, red and purple LEDs demonstrate novel bandwidths of approximately 25.23 MHz, and green and yellow LEDs exhibit unique bandwidths of 23.75 MHz and 9.62 MHz, respectively. The attenuation parameters for different wavelengths provide numerous insights, showcasing the novelty of this research and its potential applications in robot communication within plastic pipes. Concurrently, the paper introduces an approach to address the temperature impact on five distinct wavelength LEDs in OWC. By focusing on variations in LED bandwidth and optical power, an optimal heat sink design is proposed. This design achieves a remarkable minimum temperature of 27.06°C and reduces the chip LED device’s response time from 15 to 9 seconds. The significance lies in the novelty of the proposed heat sink, which incorporates variables such as fin thickness, height, air gap width, number of fins, and airflow rate, marking a substantial advancement in thermal management for OWC systems.

Optical wireless communication (OWC) has emerged as a promising solution to the radio spectrum crunch. OWC technology requires more access points (APs) compared to other wireless technologies, making it crucial to have reliable OWC APs to ensure low repair rates and optimal network availability. To address this, our paper provides methods to enhance the reliability of duplex OWC AP transceivers and calculates their reliability parameters. The transceiver design consists of several independent modules, and we calculate the failure in time (FIT) for each module using MTBF calculator software and component datasheets. Our reliability analysis includes two methods: mean time between failure (MTBF) calculations using reliability block diagrams and Markov chain modeling. The former identifies modules with a high failure rate and determines the system’s cumulative downtime or repair time, while the latter accounts for the repair rates of individual modules for availability calculations. Both methods complement each other and provide insight into fault-tolerant system designs. Furthermore, we perform a life cycle cost analysis of the proposed fault-tolerant transceiver designs to facilitate appropriate design choices for different applications.

The combined use of distributed multiple-input multiple-output (D-MIMO) and orthogonal frequency division multiplexing (OFDM) with adaptive bit and power loading is seen as a powerful tool to overcome limitations of the optical wireless communication (OWC) channel and of light-emitting diodes (LED)s. Although extensive research into efficient MIMO algorithms has been performed for communications via radio, these may not be indiscriminately re-used in LED-based OWC systems. The main reasons are that the OWC channel has different properties, the LEDs have power-constraints, and eye-safety regulations apply. For adoption in a practical system, the computational complexity of the algorithms must also be taken into account. Fortunately, physical properties of the LED D-MIMO channel allow us to reduce signalling overhead, estimation effort and complexity. This paper presents, compares, and discusses both the performance and the computational cost of several new power-loading strategies to enhance the throughput of LED-based OFDM D-MIMO OWC systems respecting the individual power constraints of the light sources. To cope with the low-pass nature of LEDs, we optimize how much power to load on each MIMO spatial stream, on each sub-carrier and what bandwidths to use. The CVX toolbox for convex optimization gives us an optimum but it is orders of magnitude more complex than highly effective heuristic approaches. A simple approach stays 1 dB short of the optimum: it equally splits power among MIMO streams within the LED power constraints, and it uniformly spreads the power over a bandwidth that is optimized per stream. A similar strategy, but selecting optimized powers per stream brings us as near as 0.1 dB to the optimum. To evaluate the complexity of bit and power allocations, we investigate, optimize, and accelerate the speed of iterative schemes. The proposed approaches give new choices for chipset manufacturers and LED-based OFDM D-MIMO OWC system designers to improve performance and to reduce overhead.

Optical wireless communication (OWC), the IEEE 802.15.7 standard (revised 2018) is developed in normative reference to low-rate wireless personal area networks IEEE 802.15.4 standard. One significant difference between the two standards is the highly directional transmitters in the OWC networks. This difference opens up the possibility of adding full-duplex communication to wireless networks. Our work proposes adding full-duplex functionality in the contention-free period (CFP) of the OWC media access control (MAC) layer. We justify the significance of our proposal by implementing IEEE 802.15.7 resource allocation scheme for both our proposed full-duplex optical MAC (FD-OMAC) and the IEEE 802.15.7 MAC. Our simulation results demonstrate that the proposed work improves the spectral efficiency in the CFP without compromising delays. We also discuss the minor changes required in the IEEE 802.15.7 MAC for implementing FD-OMAC. We further extend the FD-OMAC to a multiple access point network and evaluate its performance in comparison with IEEE 802.15.7 MAC.

This paper introduces a new hybrid waveform for optical wireless communication (OWC)/optical camera communication (OCC) systems and discusses the technical considerations of these systems. In a challenged vehicular communication environment, which requires high-speed, high-mobility, and long-distance communication support, implementing a hybrid waveform guarantees high-speed data transmission while reducing the cost of the OWC/OCC systems. The application of a hybrid waveform in the OWC/OCC systems is known as the region-of-interest (RoI)-signaling technique. This technique allows the OWC/OCC systems to simultaneously transmit low-rate and high-rate data streams. The low-rate data stream is used to detect and track the RoI of light sources for setting up the communication link, whereas the high-rate data stream is used for high-speed data transmission. Selection of proper modulation schemes for two simultaneous data streams is also discussed in this paper. A new modulation scheme, such as spatial-2-phase-shift-keying (S2-PSK), is proposed for the low-rate data stream. This scheme has been used to modify the IEEE 802.15.7-2018 standard, which is the revised version of the IEEE 802.15.7-2011 standard. For the high-rate data stream, single-carrier modulation or multiple-carrier modulation, such as the proposed hybrid-spatial-phase-shift-keying (HS-PSK) or variable pulse-position modulation (VPPM), can serve as viable solutions. Technical considerations for the modulation schemes of each type of data stream are analyzed to determine the feasibility of the proposed schemes. Finally, the experimental results and numerical parameters of the intended system are presented.

In this work, we demonstrate an integrated optical baseband, free space optical (FSO) communication and millimeter-wave (MMW) traffics through the present passive optical network (PON) architecture by utilizing single wavelength for broadcasting triple-play services. In the execution, we exploit 10 Gbit/s on-off keying (OOK) modulation on 10 GHz Mach-Zehnder modulator (MZM) to produce the downstream baseband signal. And the 10 Gbit/s baseband signal also can cause FSO traffic within the forward error correction (FEC) target after 25 km fiber and 160 m free space transmissions. Moreover, we can utilize the fiber to the extension (FTTE) scheme to provide the 36.42 GHz MMW with 10 Gbit/s OOK data after 25 km fiber link and 8 km extended fiber transmission.