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Visible light communication system based on sine function variable step size LMS equalization

A technology of visible light communication and sine function, which is applied in the direction of short-distance systems and free space transmission, can solve the problems that the curve does not have a slow change characteristic, it is difficult to achieve fast convergence, and the curve decline rate is slow, so as to increase the computational complexity, Accelerate the convergence speed and reduce the amount of calculation

Active Publication Date: 2020-07-24
TIANJIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] 1. During the convergence process, the curve decline rate is slow, and it is difficult to achieve rapid convergence;
[0007] 2. In the convergence stage, the curve does not have a gradual change characteristic, and the step size is adjusted too quickly in the steady state stage

Method used

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  • Visible light communication system based on sine function variable step size LMS equalization
  • Visible light communication system based on sine function variable step size LMS equalization
  • Visible light communication system based on sine function variable step size LMS equalization

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Experimental program
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Effect test

Embodiment 1

[0040] 1. The equalizer in the visible light communication system of the present invention includes two parts: a digital filter and an adaptive algorithm. Among them, the digital filter adopts a finite impulse response filter structure, and the adaptive algorithm adopts a least mean square (LMS) algorithm.

[0041] 2. The training sequence d(n) drives the LED to emit light through the transmitter drive circuit, and converts the electrical signal into an optical signal. After the optical signal enters the VLC channel, it is affected by inter-symbol interference and random noise v(n), and the output signal is u( n)=d(n)h(n)+v(n).

[0042] 3. In the process of signal processing, the input signal u(n) is first multiplied by the tap coefficient W(n) and summed to obtain the output signal y(n) of the filter, and then the expected signal d(n) and The output signal y(n) is subtracted to obtain the error signal e(n); then, the mean square error function required by the adaptive algori...

Embodiment 2

[0050] The visible light communication system of the present invention such as figure 1 As shown, the training sequence d(n) drives the LED to emit light through the transmitter drive circuit, and converts the electrical signal into an optical signal; after the optical signal enters the VLC channel, it is affected by inter-symbol interference and random noise v(n), and the output signal is u (n)=d(n)h(n)+v(n); then the signal u(n) passes through the photoelectric conversion circuit to convert the optical signal into an electrical signal; the electrical signal is used as the input signal of the equalizer, and the equalizer passes through the The received electrical signal is equalized so as to compensate for the visible light communication channel; the equalized electrical signal can accurately restore the original training sequence d(n) through a sampling judgment circuit. The equalizer adapts to the change of the VLC channel, and the tap coefficient reaches the optimal value ...

specific Embodiment approach

[0052] The specific implementation manner of equalizing the input signal by the equalizer in the visible light communication system is as follows:

[0053] Step 1: Initialize the tap coefficient W of the equalizer, adopt the center tap initialization method, that is, the middle tap coefficient is 1, and the rest are 0;

[0054] Step 2: Multiply the input signal u(n) by the tap coefficient W(n) to obtain the output signal y(n).

[0055]

[0056] In the formula, N is the order number of the equalizer; W is the tap coefficient.

[0057] Step 3: Subtract the expected signal d(n) from the output signal y(n) to obtain the error signal e(n).

[0058] e(n)=d(n)-y(n) (2)

[0059] Step 4: Construct the mean square error function required by the adaptive algorithm through the error signal e(n).

[0060] J=e 2 (n) (3)

[0061] Step 5: According to the basic principle of variable step size, construct the nonlinear sine function of step size factor μ(n) and error signal e(n), the ...

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Abstract

The invention discloses a visible light communication system based on sine function variable step size LMS equalization, and the system is characterized in that a training sequence drives an LED to emit light through a transmitter drive circuit during the first communication, an optical signal is affected by intersymbol interference and random noise after entering a VLC channel, and an output signal is u (n); the signal u (n) is multiplied by the tap coefficient and summed to obtain an output signal of a filter, and the expected signal is subtracted from the output signal to obtain an error signal so as to construct a mean square error function; and a step length factor and a nonlinear function of the error signal are constructed according to the sine function curve, an updating relationalexpression of the tap coefficient is constructed, and the adjusted variable step length sine function expressions of the values of alpha and beta is substituted to obtain an optimal value of the tapcoefficient so as to realize channel compensation. When communication is carried out again, an LMS initialization mode of a received signal difference value ratio is adopted, a proper tap coefficientis selected to accelerate the convergence speed, the convergence speed of the equalizer is accelerated, the tap coefficient reaches the optimal value more quickly, and compensation for a channel is realized.

Description

technical field [0001] The present invention relates to the technical field of visible light communication (Visible Light Communication, VLC) and digital signal processing, in particular to a visible light communication system that eliminates the influence of intersymbol interference, and optimizes the system through signal processing technology to improve the equalization effect of the visible light communication system . Background technique [0002] With the rapid development of today's society and the continuous popularization of mobile Internet technology, the demand for wireless communication services has increased rapidly, resulting in increasingly tight radio frequency spectrum resources. Therefore, people began to focus on higher frequency bands. The study found great potential for applications in the visible light band between infrared and ultraviolet light without the need for radio spectrum certification. As an indoor wireless transmission technology, visible l...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04B10/116
CPCH04B10/116
Inventor 谢生耿玉通毛陆虹
Owner TIANJIN UNIV
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