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Visible light communication method and system

A visible light communication and optical signal technology, applied in the field of visible light communication methods and systems, can solve the problems of reduced brightness, limited modulation bandwidth, signal distortion, etc., and achieve the effects of alleviating the reduction in information rate, maintaining high-speed communication, and reducing illumination.

Active Publication Date: 2017-04-26
BEIJING UNIV OF POSTS & TELECOMM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The method of realization is that the signal period is constant, the signal pulse width is reduced so that the duty cycle is reduced, and the average power of the transmitted optical signal is reduced, so that the brightness perceived by the human eye is reduced.
[0008] However, in the existing visible light communication, when the duty cycle of the signal is adjusted under the condition that the period is constant, the bandwidth of the signal will increase with the decrease of the duty cycle, and the modulation bandwidth of the general LED is limited, and the too low duty cycle Ratio will lead to signal distortion, resulting in the problem of low reliability of communication

Method used

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  • Visible light communication method and system

Examples

Experimental program
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Embodiment 1

[0038] The visible light communication method in this embodiment includes the steps of adjusting the illuminance:

[0039] The step of adjusting the illuminance is a step in which the transmitting end adjusts the signal period and keeps the signal pulse width constant, so that the illuminance of the transmitted light signal is not greater than a preset value. This method is usually used for the light brightness of the sending end that needs to be felt by the human eye to be very small, so as to achieve the effect of turning off the light, so the illuminance of the optical signal at the sending end needs to be less than or equal to the preset illuminance.

[0040] The sending end usually includes an LED light source. On the one hand, the LED light source can play the role of lighting, and at the same time, it is responsible for sending a signal to the receiving end through its unnoticeable on and off. When LED lighting is not needed (that is, the LED that needs to be reduced il...

Embodiment 2

[0043] In the visible light communication method of this embodiment, the sending end of the visible light signal includes the step of adjusting the illumination;

[0044] The illuminance adjustment step: adjusting the signal cycle and keeping the signal pulse width constant, so that the illuminance of the transmitted light signal is not greater than a preset value;

[0045] After the illuminance adjustment step, the sending end calculates the duty cycle of the light signal and expresses it in the form of a power, the duty cycle is greater than or equal to 2 -n and less than 2 -(n+1) Between, use L-PPM modulation to generate the transmitted optical signal, where L=2 n , n is a positive integer, so that when the illuminance of the transmitted visible light decreases, the information transmission rate of the system will not decrease rapidly.

[0046] PPM: Plus Position Modulation pulse position modulation, when the signal period T PWM extended for pulse width T PWM(ON) 4 time...

Embodiment 3

[0049] Such as figure 2 As shown, the visible light communication method of this embodiment includes the following steps in sequence:

[0050] Step S1: Before switching the signal period and modulation mode, the sending end sends an information frame including switching of the signal period and modulation mode;

[0051] Step S2: The receiving end receives and changes the signal period and demodulation mode according to the information frame, and replies confirmation information to the sending end;

[0052] Step S3: After receiving the confirmation information, the sending end switches the signal period and modulation mode. When a sending end needs to communicate with several receiving ends, the sending end communicates with each receiving end through time-division multiplexing, and the switching is completed in sequence.

[0053] Step S4: Adjusting the signal cycle and keeping the signal pulse width constant to ensure that when the illuminance of the transmitted optical sig...

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Abstract

The invention discloses a visible light communication method and system which aim to solve the problem that in the prior art of visible light communication, communication stability is poor during low illumination. According to the visible light communication method, the sending end of a visible light signal includes illumination adjustment steps, and the illumination adjustment steps include adjusting of a signal cycle and maintaining of constancy of a signal pulse width, so that illumination of the sent light signal is not larger than a preset value. The visible light communication system comprises a sending end and a receiving end, wherein the sending end comprises a signal cycle changing unit, and the signal cycle changing unit is used for adjusting the signal cycle and maintaining constancy of the signal pulse width, so that the illumination of the sent light signal is not larger than the preset value. The visible light communication method and system have the advantages of being good in communication continuity, high in communication quality, easy to achieve and the like, and is especially suitable for visible light communication under variable illumination.

Description

technical field [0001] The present invention relates to the field of wireless optical communication, in particular to a visible light communication method and system. Background technique [0002] Visible Light Communications (VLC) is a wireless optical communication that uses white LEDs as light sources, photoelectric conversion devices or optical imaging devices as photodetectors, and the atmosphere as a channel to modulate transmission signals on visible light emitted by LEDs. technology. [0003] Because compared with traditional light sources such as incandescent lamps and fluorescent lamps, LEDs have a much wider modulation bandwidth and can be switched at a higher frequency, which makes it possible to use LEDs as light sources for high-speed communication. Due to the very high modulation frequency, the flickering of the light is not perceptible to the human eye. Usually, visible light communication can be used as the second function of LED lights to complete communi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B10/00H04B10/11
Inventor 张明伦贾银杰陈锟宫树月
Owner BEIJING UNIV OF POSTS & TELECOMM
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