Exploring the Potential of Utilizing Nonline-of-Sight Channels for Networking in Visible Light Communication

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Jiacheng Wu, Pinpin Zhang, Yiling Huang, Chang Liu, Yimao Sun, Chen Chen, Yanbing Yang, Jun Luo

Published: 01 Jan 2025, Last Modified: 10 Nov 2025IEEE Internet Things J. 2025EveryoneRevisionsBibTeXCC BY-SA 4.0
Abstract: Visible light communication (VLC), as one of the key technologies for new spectrum communication in 6G, has drawn much attention from both academia and industry. The femtocell-like deployment of VLC in indoor environments gives rise to the concept of optical attocells, where each light-emitting diode (LED) serves as an optical access point (AP), enabling illumination and communication simultaneously. However, the majority of existing optical attocell networks rely on wired backbone links (e.g., Ethernet or power-line connections) for interattocell connectivity, and this dependency renders the overall network vulnerable to backbone link failures. To this end, we introduce a novel network architecture that exploits the inherent nonline-of-sight (NLOS) optical channels between adjacent attocells to enable interattocell communication, enhancing network resilience and flexibility. In particular, we design a chirp signal based on chirp spread spectrum (CSS) modulation tailored for intensity-modulated VLC to improve the noise resilience in NLOS channels for reliable communication under low-signal-to-noise ratio (SNR) conditions. Moreover, we propose a two-stage window alignment approach that integrates coarse-grained with fine-grained alignment to achieve precise synchronization while reducing real-time decoding latency. Finally, we build two prototypes of NLOS optical attocells based on different hardware platforms and conduct extensive field experiments using three modulation schemes, i.e., on-off keying (OOK), frequency-shift keying (FSK), and CSS, to evaluate their performance under variable parameters. Experimental results indicate that the CSS modulation scheme demonstrates superior robustness than the other two schemes, achieving bit error rates (BER) of $3.1\times 10^{-5}$ and $8.3\times 10^{-5}$ , and packet reception rates (PRR) of 98.53% and 99.71% on two platforms, respectively, at a horizontal distance of 8 m between adjacent optical devices.