Visible Light Communication
The visible light communication (VLC) system not only meets the needs of indoor lighting, but also has wireless communication functions. Its advantages such as no radio frequency electromagnetic radiation, no need for spectrum authentication, low cost, high confidentiality, high modulation bandwidth, and high-speed transmission rate have promoted the rapid development of this technology.
Classification of Wireless Communication Technologies
Wireless access technologies typically include Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and Time Division Multiple Access (TDMA). Although FDMA technology can provide a large continuous bandwidth, it requires transmitting and receiving hardware units to filter optical signals of different wavelengths, which increases hardware complexity and is not easy to flexibly configure, thereby limiting the number of access nodes; CDMA technology requires the signal carrier to have rich phase details, while the VLC system in this article uses open key control (OOK) modulation technology, which does not have sufficient phase variation to meet the requirements of CDMA. Therefore, adopting TDMA as the preferred solution for multi-user access allows for flexible configuration of user access numbers. In theory, this technology can support more user access by adjusting data throughput and latency performance, and can flexibly set data rates for each user as needed.
Indoor VLC Network Based on TDMA
For indoor practical application scenarios, by designing the light source density and power reasonably, communication and positioning functions can be achieved while ensuring lighting requirements. In addition, it is very necessary to build a VLC network integrated with the Internet while taking into account the cost, engineering difficulty and other factors. A TDMA based indoor VLC network that supports flexible access and resource allocation for multiple mobile users, enabling dynamic allocation of limited bandwidth resources within the VLC network and improving resource utilization.
TDMA based visible light network access and network maintenance method
For indoor VLC, a TDMA mechanism can be used to design a visible light network access and network maintenance method, describe the detailed competitive access and network maintenance process, and analyze the access probability of this method. The probability of 5 mobile terminals accessing the network in each time slot is 0.15625, theoretically, 7 time slots can ensure one terminal accessing the network. In the experiment, 10 time slots were designed to ensure the network access time of one terminal, so the time required for all 5 terminals to access the network is 25ms. Through laboratory verification, the network access and maintenance method can support flexible access and dynamic resource allocation for multiple users, and the engineering implementation is simple.