Intelligent traffic system based on visible light communication
An intelligent transportation system and visible light technology, applied in the field of intelligent transportation systems based on visible light communication, can solve the problems of wireless Wi-Fi technology security risks, low feasibility, high network access costs, etc.
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Embodiment 1
[0022] image 3 For signal reception sampling schematic diagram in the present invention, light-emitting diode LED13 sends out data packet, and photodiode 14 is connected FPGA6 and finishes clock synchronization by stepping amplifier 12, guarantees the time accuracy that sampling takes place; The photodiodes 14 have the same cycle, and the delay in sending a single data within one cycle does not exceed 3ms. In the receiving process, the clock of photodiode 14 is ahead of 1 / 4 of the light-emitting period of LED13. When LED13 emits logic "0" (low light density), photodiode 14 starts to sample 1; when LED13 sends logic "1" (high light density), Photodiode 14 starts sampling 2, and FPGA 6 compares the two samples.
Embodiment 2
[0024] image 3 In the curve of photodiode PIN.D3, the energy of photodiode PIN.D3 sampling 1 and 2 is equal, and the clock phase of LED13 and photodiode PIN.D3 exceeds two sampling periods. Optical density is too low. Therefore, the communication algorithm should include ensuring that at least one of the two sampled signals is detected as a logic "1". For example, if the sampling signals 1 and 2 do not exceed the determined threshold, FPGA6 recognizes that the clock is off for 2 cycles, and adjusts the clock; if after adjustment, the sampling signals 1 and 2 still do not exceed the threshold, it is determined that there is currently no light source input synchronization signal mode.
Embodiment 3
[0026] The optional wavelength range of LED13 lamps is 850nm, 1310nm, 1490nm, CW-DM, 1550nm, DWDM; the activation method is light sensor start, passive light start, light and sound control combination technology, light sensor mechanical integration module and / or optional technology choose.
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