Visible Light Communication (Part – 1)

What is VLC?

Visible Light Communication system (VLC) is dual use of illumination and communication concept. VLC concepts are that the data is propagated through a visible light wave. Visible Lightwave produced by LED or LASER. But LED has many advantages like energy savings and longer lifespans and also other benefits. Usage of LED is increased exponentially. LED has a short range of illumination so that it can be used in indoor environments for both purpose illuminations as well as communication. The LEDs are capable of switching to different light intensity levels at a very fast rate. The switching rate is fast enough to be imperceptible by a human eye. This functionality can be used for communication where the data is encoded in the emitting light in various ways. A photodetector or an image sensor (matrix of photodiodes) can receive the modulated signals and decode the data. Visible Light Communication provides many benefits. First visible light spectrum in Figure 1 includes hundreds of terahertz of license-free bandwidth which is completely untapped for communication. Second due to its high frequency, visible light cannot penetrate through most object and walls. It can also increase the capability of an available wireless channel. Third, VLC facilitates the reuse of existing lighting infrastructure for purpose of communication.

In MIMO VLC system, as the number of transmitters and receivers increases, large adjacent channel interference is introduced. The adjacent channel interference is helpful to achieve the higher strength of a signal at receiver side due to use of MIMO diversity repetition coding technique. Repetition coding means simply transmit same data by multiple transmitters.

spectrum of VLC
In this section, we discuss equalizer, which is used for removing Inter-Symbol Interference (ISI). Performance of MIMO VLC can also be increased by applying different equalizer. The type of simple equalizer is the Zero Forcing (ZF) and Minimum Mean Squared Error (MMSE). We can also improve the performance of the system by adding the Successive Interference Cancellation (SIC) approach to the equalizer. ZF – SIC and MMSE – SIC equalizers give better performance because SIC uses adjacent channel interference to improve the performance of MIMO VLC system. For remove perfect effect of Inter-Symbol Interference (ISI), we use optimal ordering in a different equalizer. All different equalizers applied in MIMO VLC system, and the related simulations have been implemented in MATLAB.

One thought on “Visible Light Communication (Part – 1)”

  1. Hi Sir,
    Thank You for comment on VLC SNR code for Matlab. After which I started searching for you and landed here. The content here is really great. Thank You so much for it.

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