Patent ID: 11909440
Assignee: SOOCHOW UNIVERSITY
Field: Telecommunications (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 6:
7. A modulation and demodulation method for a visible light communication system with adaptive dimming, based on the visible light communication system with adaptive dimming according to claim 1, comprising steps of:
obtaining optimal light intensity I0 of an LED lamp of a light emitter upon delivery;
acquiring average light intensity Ii of the LED lamp within one transmission period by using a photoelectric sensor;
calculating actual real-time light intensity attenuation di=(I0−Ii)/Io, and performing weighted operation according to theoretical light intensity attenuation d(t) corresponding to use time of the LED lamp in a light attenuation curve of the LED lamp upon delivery, to obtain light attenuation D=w1di+w2d(t), wherein w1 and w2 are weights;
dividing the light attenuation D into N levels, wherein N is determined by bandwidth of the LED lamp, it is specified that N=BW/100k, and a range of the light attenuation D on an nth level is, n
     -
     1
    
    N
   
   ~
   
    n
    N
   
   ×
   100
   ⁢
   %
  
  ;
 

calculating, by an emitter controller, an order M=[32/n];
when the emitter controller detects that the order M needs to be changed, transmitting, by the emitter controller, a changed modulation order M′ to an adaptive M-PAM modulator;
controlling, by the adaptive M-PAM modulator, the light emitter to use the current order M to emit a light signal with an order that needs to be changed, wherein the light signal with an order that needs to be changed carries the changed order M′;
converting, by a photoelectric sensor of a receive end, the light signal carrying the modulation order M′ into an electrical signal carrying the modulation order M′;
obtaining, by a receiver controller, the electrical signal carrying the modulation order M′, and obtaining the demodulation order M′ according to the electrical signal carrying the modulation order M′; and
transmitting, by the receiver controller, the demodulation order M′ to the adaptive M-PAM demodulator, and demodulating, by the adaptive M-PAM demodulator, a communication signal according to the demodulation order M′.