Self-adaptive dimming visible light communication system and modulation and demodulation method

Abstract

The invention relates to a self-adaptive dimming visible light communication system and a modulation and demodulation method. The system comprises an information source; a self-adaptive M-PAM modulator which modulates a signal sent by the information source into a first electric signal and a second electric signal respectively; a double-path pulse generator which alternately generates a first pulse control signal and a second pulse control signal, with the first pulse control signal and the second pulse control signal being both periodic signals; when the remaining working time of the high level of the first pulse control signal is equal to the time of the rising edge of the second pulse signal, starting generation of the second pulse control signal; when the remaining working time of the high level of the second pulse control signal is equal to the time of the rising edge of the first pulse signal, starting generation of the first pulse control signal. Non-interval and non-delay switching of visible light and infrared double-path signals is realized, and the self-adaptive M-PAM modulation signal can be loaded at any time.

Description

technical field [0001] The present invention relates to the technical field of optical communication, in particular to an adaptive dimming visible light communication system and a modulation and demodulation method. Background technique [0002] With the development of 5G and big data technology, people have higher demands on the speed and coverage of the network. For traditional electromagnetic wave communication, due to its inability to penetrate metals and limited spectrum resources, it is impossible to achieve signal coverage transmission for metal airtight and electromagnetic shielding spaces. In recent years, the indoor visible light communication system using LED has become a popular technology to solve the traditional electromagnetic wave communication due to its advantages of high speed, safety, energy saving and environmental protection, and rich spectrum resources. Although the visible light communication system has both lighting and communication functions, the ...

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Problems solved by technology

And this system does not consider the delay time of the rising edge and falling edge of the actual MPPM signal. In actual situations, the transmission of OFDM signals is easily interfered by the rising and falling edges, so the theoretical high transmission rate and low bit error rate cannot be achieved.

[0007] 2. For a visible light OFDM communication system that uses infrared compensation for full-range dimming, the rising and falling edges of the dimming pulse signal limit the alternate transmission of visible light and infrared signals

The step response characteristics of existing commercial visible light lighting LEDs and infrared emitters are poor. If the delay time of rising and falling edges of high and low levels is not considered, the rate and quality of alternate transmission will be greatly reduced, and this technical solution cannot be effective Filter out the falling edge signal interference of visible light and infrared LED. In certain pulse modulation modes with specific duty cycles, the bit error rate and transmission rate are not even as good as those without infrared compensation.

[0008] 3. The visible light OFDM communication system using infrared compensation and full-range dimming cannot separate visible light and infrared signals at the receiving end, and the two signals will interfere at the receiving end, increasing the bit error rate

[0009] 4. The complexity of OFDM is high, especially when the real-time system is realized, the research and development cycle is long

Moreover, the peak average of OFDM signals is relatively high, which requires a large linear working area of ​​the light source, resulting in a large maximum transmission power, and at the same time, the cost of devices and drive circuits will also increase, and greater power will bring worse frequency response, will reduce the bandwidth

In addition, with the accumulation of LED usage time, the OFDM signal cannot automatically adapt to the lamp beads whose performance is degraded due to aging, resulting in signal distortion and increased bit error rate.

The use of OFDM signals can only increase the rate in an ideal experimental environment, and is not suitable for specific practical application scenarios

[0010] 5. In the prior art, the rising edge and falling edge delay time in the actual implementation process of the system, that is, the preparation time, will lead to problems such as reduced transmission efficiency, mutual interference between two-way mixed signals, and increased bit error rate.

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