FSK Modulated LED Waveform for Indoor Navigation Flicker Avoidance
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Solution Overview
Problem
Existing communication technologies face challenges in transmitting data using amplitude-modulated light sources without causing perceivable flicker to the human eye and efficiently decoding data with low sampling rates, particularly in indoor navigation applications like smart shopping systems.
Innovation Solution
The system varies the frequency of an amplitude-modulated light source, employing frequency shift keying (FSK) to encode data, which is then received and decoded by a device with a low sampling frequency, such as a smartphone camera, using undersampling to alias frequency components for image processing, thereby avoiding noticeable flicker and enabling data transmission through modulated LED lighting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If amplitude modulation frequency is increased to prevent perceivable flicker, then human eye perceivability of flicker is reduced, but data transmission rate and decoding efficiency deteriorate due to limitations of low sampling rate devices
Solution Approach 1:
The patent changes the modulation frequency parameter to a high frequency range (e.g., above 100 Hz) that is imperceptible to the human eye, while simultaneously employing frequency shift keying with specific frequency offsets that can be detected through undersampling. This allows the system to operate at frequencies that avoid flicker perception while maintaining decodability by low sampling rate devices through the aliasing effect.
Solution Approach 2:
The patent employs periodic amplitude modulation with specific frequency patterns that create distinguishable aliases during undersampling. By using periodic modulation at high frequencies with carefully selected frequency shifts, the system creates a periodic structure that can be reliably detected and decoded even when sampled below the Nyquist rate, thus maintaining data transmission capability while avoiding perceivable flicker.
2Object-affected harmful factors
If high frequency modulation is used to avoid perceivable flicker, then flicker perception is eliminated, but device complexity increases due to the need for frequency shift keying and undersampling processing
Solution Approach 1:
The patent leverages the natural aliasing effect that occurs during undersampling as a beneficial phenomenon rather than treating it as an error condition. The high frequency modulation naturally aliases to lower frequencies when sampled by low sampling rate devices, and the system is designed to exploit this aliasing for reliable detection. This self-service approach eliminates the need for complex anti-aliasing filters or high-speed sampling hardware, reducing overall system complexity while avoiding perceivable flicker.
3Use of energy by moving object
If low sampling rate devices are used for data reception, then device cost and power consumption are reduced, but measurement precision and data decoding reliability deteriorate
Solution Approach 1:
The patent changes the modulation scheme to frequency shift keying with specific frequency relationships that create distinct alias patterns detectable by low sampling rate devices. By carefully selecting modulation frequencies and their shifts, the system ensures that the aliased signals maintain sufficient frequency separation and amplitude characteristics that can be reliably distinguished and decoded, thus maintaining measurement precision despite the low sampling rate.
Solution Approach 2:
The patent incorporates feedback mechanisms in the decoding process where the receiver adjusts its detection parameters based on the observed alias patterns. By monitoring the received signal characteristics and adapting the decoding threshold and frequency estimation accordingly, the system compensates for the limitations of low sampling rate devices, maintaining high decoding accuracy while operating with reduced power consumption hardware.
Data Source
AI summary
Embodiments may provide a way of communicating via an electromagnetic radiator, or light source, that can be amplitude modulated such as light emitting diode (LED) lighting and receivers or detectors that can determine data from light received from the amplitude modulated electromagnetic radiator. Some embodiments may provide a waveform in the form of chips at a chipping clock frequency that switch a light source between on and off states to communicate via light sources that can be amplitude modulated such as LED lighting. Some embodiments may provide a method of transmitting the waveform via modulated LED lighting. Some embodiments are intended for indoor navigation via photogrammetry (i.e., image processing) using self-identifying LED light anchors. In many embodiments, the data signal may be communicated via the light source at amplitude modulating frequencies such that the resulting flicker is not perceivable to the human eye.