Light-emitting diodes (LEDs) have emerged as a critical component in light fidelity (Li-Fi) systems, offering a high-speed wireless communication alternative to traditional radio frequency (RF) methods. Li-Fi leverages the visible light spectrum for data transmission, providing advantages in bandwidth, security, and energy efficiency. The core of Li-Fi technology relies on the rapid modulation of LEDs to encode data, efficient multiplexing techniques to maximize channel capacity, and specialized receiver designs to decode optical signals. A comparison with RF communication highlights the distinct benefits and challenges of Li-Fi systems.

Modulation bandwidth is a fundamental parameter in Li-Fi systems, determining the maximum achievable data rate. LEDs exhibit a modulation bandwidth typically ranging from a few megahertz to several hundred megahertz, depending on the material and device design. For instance, commercial phosphor-coated white LEDs have a limited bandwidth of around 3-5 MHz due to the slow response time of the phosphor layer. In contrast, gallium nitride (GaN)-based micro-LEDs can achieve bandwidths exceeding 100 MHz, enabling gigabit-per-second data rates. The modulation techniques employed include on-off keying (OOK), pulse-position modulation (PPM), and orthogonal frequency-division multiplexing (OFDM). OFDM is particularly advantageous as it mitigates inter-symbol interference in multipath environments and maximizes spectral efficiency.

Multiplexing techniques enhance the capacity of Li-Fi systems by allowing multiple data streams to coexist within the same optical channel. Wavelength-division multiplexing (WDM) utilizes different colors of LEDs to transmit independent data streams simultaneously. For example, red, green, and blue micro-LEDs can each carry separate OFDM signals, tripling the aggregate data rate. Spatial-division multiplexing (SDM) employs multiple transmitters and receivers to exploit spatial diversity, improving link robustness and throughput. Another approach, termed non-orthogonal multiple access (NOMA), enables multiple users to share the same time-frequency resources by superimposing their signals with different power levels. These techniques collectively enable Li-Fi to support high-density communication scenarios, such as indoor environments with numerous connected devices.

Receiver design in Li-Fi systems must account for the unique characteristics of optical wireless channels. Unlike RF receivers, which rely on antennas, Li-Fi receivers use photodiodes or imaging sensors to detect modulated light. However, since the discussion excludes photodetectors, the focus shifts to signal processing and decoding strategies. Adaptive equalization compensates for channel distortions caused by multipath propagation, while machine learning algorithms can optimize demodulation in dynamic lighting conditions. Furthermore, angle diversity receivers mitigate the impact of ambient light interference by selectively capturing signals from specific directions. The receiver’s field of view and sensitivity are critical parameters that influence the system’s performance, particularly in mobile scenarios where alignment between transmitter and receiver may vary.

Contrasting Li-Fi with RF communication reveals several key differences. RF systems operate in crowded spectral bands, leading to congestion and interference, whereas Li-Fi exploits the vast and underutilized visible light spectrum. The inherent directionality of light enhances security, as signals are confined within physical boundaries, reducing eavesdropping risks. However, Li-Fi faces challenges such as limited range and susceptibility to obstructions, whereas RF signals penetrate walls and cover larger areas. Energy efficiency is another distinguishing factor; LEDs consume less power than RF transmitters while simultaneously providing illumination and data transmission.

In summary, LEDs serve as the backbone of Li-Fi systems, enabling high-speed wireless communication through advanced modulation schemes, multiplexing techniques, and optimized receiver designs. While Li-Fi offers distinct advantages over RF in terms of bandwidth and security, its practical deployment requires addressing challenges related to coverage and mobility. Continued advancements in LED technology and signal processing will further solidify Li-Fi’s role in future wireless networks.