Channel Characteristics and Link Adaption for Visible Light Communication in an Industrial Scenario

Abstract

Visible light communication (VLC) is one of the key technologies for the sixth generation (6G) to support the connection and throughput of the Industrial Internet of Things (IIoT). Furthermore, VLC channel modeling is the foundation for designing efficient and robust VLC systems. In this paper, the ray-tracing simulation method is adopted to investigate the VLC channel in IIoT scenarios. The main contributions of this paper are divided into three aspects. Firstly, based on the simulated data, large-scale fading and multipath-related characteristics, including the channel impulse response (CIR), optical path loss (OPL), delay spread (DS), and angular spread (AS), are analyzed and modeled through the distance-dependent and statistical distribution models. The modeling results indicate that the channel characteristics under the single transmitter (TX) are proportional to the propagation distance. It is also found that the degree of time domain and spatial domain dispersion is higher than that in the typical rooms (conference room and corridor). Secondly, the density of surrounding objects and the effects of user heights on these channel characteristics are also investigated. Through the analysis, it can be observed that the denser objects can contribute to the smaller OPL and the larger RMS DS under the single TX case. Furthermore, due to the blocking effect of surrounding objects, the larger OPL and the smaller RMS DS can be observed at the receiver with a low height. Thirdly, due to the distance dependence of the channel characteristics and large time-domain dispersion, the link adaption method is further proposed to optimize the multipath interference problem. This method combines a luminary adaptive selection and delay adaption technique. Then, the performance of the link adaption method is verified from four aspects through simulation, including the signal-to-noise (SNR), the RMS DS, the CIRs, and the bit-error rate (BER) of a direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) system. The verification results indicate that our proposed method has a significant optimization for multipath interference.

Sixth-Generation (6G) Networks for Improved Machine-to-Machine (M2M) Communication in Industry 4.0

“…It is necessary to take into account the environment and link adaptation to optimize the multipath interference problem. The signal-to-noise ratio (SNR), RMS DS value, CIR coefficients, and bit error rate (BER) have been proposed as key parameters for the selection of a solution [19]. Wireless sensor networks (WSNs) are increasingly using hybrid RF-VLC cognitive systems, for WSNs with cognitive radio sensor networks (CRSNs) and VLC.…”

A Review of Cognitive Hybrid Radio Frequency/Visible Light Communication Systems for Wireless Sensor Networks

“…For instance, a CR-inspired approach could dynamically optimize the VLC system parameters in response to prevailing propagation conditions. Additionally, CR tactics for mitigating multi-path fading, such as employing diversity techniques, can be adapted to handle reflections in VLC systems [ 67 ].…”

“…Paper [ 67 ] concentrates on VLC channel characteristics and its application in an industrial environment, proposing adaptive techniques for performance optimization. Similar principles of adaptability and optimization apply to both VLC and CRSNs.…”

Experimental Demonstration of a Visible Light Communications System Based on Binary Frequency-Shift Keying Modulation: A New Step toward Improved Noise Resilience

“…Acknowledging the benefits of OFDM, and also the fact that its use can generate high peak-to-average power ratio (PAPR), the authors of [45] propose and evaluate a PAPR reducing algorithm based on a Vandermonde-like matrix combined with a Gaussian matrix, providing a 11-34% PAPR reduction with respect to other methods. The authors of [46] focus on the use of the VLC technology in an industrial IoT scenario. After using ray tracing to demonstrate that this environment is more challenging than the standard indoor utilization scenario, they propose a link adaptation mechanism aimed at reducing the effects of multipath interference.…”

“…Again, DC OFDM is considered as a suitable modulation technique. It should be emphasized that [44][45][46], as well as most of the works that are focused on different types of modulation evaluation are based on simulations, whereas the VLC channel model provided in [47] remains the basis for most of today's channel models. Different from FSK-based modulation such as OFDM, the work focused on phase-shift keying (PSK) modulation is rather limited, with only few such papers being available [48,49].…”