Visible Light Receiver Phase Synchronization Under Optical Noise
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Solution Overview
Problem
Existing synchronization methods in visible light communication systems, particularly in noisy environments, fail to achieve precise alignment of the phase of the periodic signal generated by the receiver with that of the transmitter, leading to high synchronization error probabilities and steady-state phase errors due to interference and noise from light pollution.
Innovation Solution
A receiver is designed to synchronize with a transmitter using Andronov-Hopf oscillators, employing a feedback loop and a processing circuit to generate periodic output pulses based on received signals, reducing noise through pre-processing and implementing a feedback loop to synchronize the phase of the receiver with the transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LED intensity is modulated at high frequencies for visible light communication, then data transmission capability is improved, but human perception of light flicker increases and comfort deteriorates
Solution Approach 1:
The patent applies periodic action by using dual-frequency modulation where the LED is modulated at two different frequencies simultaneously. The first frequency carries the data signal while the second frequency serves as a reference signal. This periodic modulation approach enables synchronous detection at the receiver, allowing accurate signal recovery without requiring the modulation frequency to be excessively high, thereby reducing perceptible flicker while maintaining data transmission capability.
2Productivity
If LED modulation frequency is increased to improve communication bandwidth, then data rate is improved, but power consumption increases
Solution Approach 1:
The patent implements continuity of useful action through continuous transmission of both data signal and reference signal at optimized frequencies. By maintaining continuous synchronous detection rather than intermittent high-frequency bursts, the system achieves reliable data transmission at moderate frequencies, avoiding the exponential power increase that would result from continuously operating at maximum modulation frequencies.
3Reliability
If synchronous detection is implemented to improve signal detection accuracy, then communication reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses a reference signal as an intermediary element that facilitates synchronous detection. The reference signal, transmitted alongside the data signal at a distinct frequency, acts as a mediator that enables the receiver to synchronize its detection process. This intermediary approach simplifies the detection mechanism compared to complex signal processing methods, as the receiver can use the reference signal to establish synchronization without requiring sophisticated algorithms or additional hardware complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces synchronization error probability and steady-state phase errors, ensuring precise alignment even in high-noise environments by modeling the transmitter and receiver as Andronov-Hopf oscillators and using a feedback loop to converge the receiver's phase with the transmitter's phase.
Implementation Method 1
A transmitter modulates an intensity of the LED at a first frequency with a data signal
Implementation Method 2
A receiver recovers the data signal from the LED light with a photodetector
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a receiver (5) designed for visible light communication and to be synchronised with a transmitter (3). The transmitter (3) and the receiver (5) each adopt the behaviour of an Andronov-Hopf oscillator in order to perform a synchronisation method. The receiver (5) comprises: - a photoreceiver (11) arranged to receive a signal corresponding to a periodic input pulse transmitted by the transmitter (3) and capable of being corrupted by noise, and - a processing circuit (15) arranged to disrupt the behaviour of the receiver (5) with a coupling input generated from the received signal and to generate a periodic output pulse by implementing a loop for controlling the periodic output pulse to the received signal in order to synchronise the phase of the receiver (5) with that of the transmitter (3).