Novel integrated visible light communication and positioning systems

Abstract

With the advent of 5G and the impending demands of 6G networks, the limitations of traditional radio frequency (RF) communication, such as spectrum congestion and electromagnetic interference, have become increasingly apparent. Visible light communication (VLC) offers a promising solution by utilizing the vast and unregulated visible light spectrum for high-speed and low-latency data transmission. Concurrently, visible light positioning (VLP) leverages existing lighting infrastructure to achieve precise indoor positioning. Integrating VLC and VLP into a unified visible light communication and positioning (VLCP) system not only simplifies the overall system but also optimizes resource utilization and enhances performance. However, VLCP systems face challenges including signal interference, synchronization dependency, complex design requirements, and resource allocation issues. To address these, we propose several innovative VLCP system designs. Firstly, we employ the code division multiplexing (CDM) approach to integrate VLC and VLP into a single system with low complexity. To reduce synchronization dependency in CDM-based VLCP system, we design a kind of orthogonal pseudo-random code (OPRC) with perfect cross-correlation properties. The effectiveness of OPRC to maintain the signal's orthogonality is preliminarily verified in an asynchronous CDM (ACDM)-based VLP system which achieves sub-centimeter average positioning errors without any synchronization requirements. Next, to further enhance the system's functionality for both communication and positioning, we introduce a successive interference cancellation decoding (SICD) strategy. This approach effectively mitigates multiple access interference (MAI) caused by chip offset and multi-bit information interleaving, significantly improving ACDM-based VLCP system's performance. Simulation results confirm that the proposed scheme meets the requirements for high-precision indoor positioning while ensuring error-free data transmission in the asynchronous VLCP system. Next, to enhance the stability and practicality of CDM-based VLCP systems in more complex indoor environments, we design a VLCP system leveraging the multi-carrier orthogonal coding mechanism (MC-OCM) based on complete complementary (CC) codes. Each CC code consists of multiple sub-codes transmitted simultaneously through independent channels, facilitated by a designed multi-carrier transmission mechanism. Utilizing the superior correlation properties of CC codes, our system ensures interference-free transmission from MAI and inter-symbol interference (ISI) in asynchronous environments, thus improving both data transmission quality and receiver location precision. Numerical analysis across diverse scenarios validates the proposed VLCP system's superiority, especially in challenging environments with asynchronous transmission and multipath propagation. Finally, to address resource utilization and user capacity limitations in CDM-based VLCP systems, we propose a multi-user VLCP system using the dual-domain multiplexing (DDM) scheme. This approach combines time and code domain resources for efficient simultaneous VLCP signals transmission to multiple users. Specifically, each user is allocated a unique orthogonal code for data differentiation via CDM, while time division multiplexing (TDM) separates VLCP signals emitted by different LED transmitters in different time slots, thereby preventing signal interference and optimizing resource utilization. Experimental data demonstrate the system's feasibility, showing that with four LED transmitters, the system can support up to eight users with a low-speed VLC and a high-precision positioning accuracy of up to 2 cm, which also overcomes the user capacity bottlenecks of traditional CDM-based VLCP systems.