Improving Efficiency of a Wireless Optical Data Transmission Channel in the Visible Wavelengh Range

Abstract

The article is devoted to the study of a wireless optical communication channel in the visible wavelength range. In the first part of the study, an original method for encoding binary data stream based on QPSK quadrature phase shift keying and color separation in a wireless optical communication channel in the visible range has been proposed. A unique feature of the proposed method is the independence of the light intensity and color hue of the bit sequence values. The proposed method has improved speed and an error detection mechanism in the channel. In addition, the developed coding method is suggested as a source of information for adaptive power control of the luminous flux on the basis of monitoring the state of each of the color components, and the synchronization problems of the receiver and the transmitter are considered. These features allow us to implement the proposed method of coding and dynamic control of the intensity for the luminous flux in artificial light sources based on RGB LEDs for the organization of wireless data transmission channels, to use these light sources in rooms with combined lighting. The paper also contains the estimate result of the maximum distance at which recognition of an optical signal is possible based on the quantum threshold of detection. Estimation of errors in an optical channel, as well as the level of general illumination by lamp or sunshine light sources in the room will dynamically change the optical signal level (or sensitivity of the photodetector) and ensure the required security of information during its transmission in controlled space based on the quantum threshold value detection. Keywords-wireless data transmission, optical data transmission channel in the visible wavelength range, quantum threshold of optical emission detection, color channel, encoding based on quadrature phase shift keying.

Development of Method for Increasing Sensitivity in Wireless Optical Data Transmission Channels in Visible Wavelength Range

“…The encoding method assumes that in one reference signal period, each color channel will generate one pulse of equal duration and all three color components will have different phases. Simultaneous presence of two or three pulses of different colors at the input will signal the presence of interference or occurrence of "illumination" -change of intensity of additional natural or artificial lighting [8]. Here, it is necessary to distinguish short-term pulses Such method ensures control and possibility of dynamic compensation of external "illumination" by changing the gain of photo-detectors and adjusting the brightness of emitting LEDs.…”