Visible Light Communication Using Rolling-Shutter Signal Encoding
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Solution Overview
Problem
Existing communication methods, particularly in visible light communications, face challenges in maintaining high data transmission rates without noticeable flickering of the light source and suffer from degradation in data rate performance due to dimming, especially at high dimming levels, and require efficient power management to reduce power consumption.
Innovation Solution
The use of a detection system with a radiation detector comprising multiple sensing elements that sample differing subsets of sensing elements at varying times to determine data encoded in a radiation signal, employing techniques such as SIM-OFDM and spatial modulation to improve bit error rate performance and power efficiency, while allowing for common apparatus usage like digital cameras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transmitting light source is switched between intensity levels at a high rate to achieve high data transmission rates, then the data transmission rate is improved, but noticeable light flickering occurs
Solution Approach 1:
The patent applies periodic action by modulating the light source intensity at specific rates that correspond to the camera's rolling shutter scan rate. The light intensity is varied periodically in synchronization with the camera's line-by-line scanning process, allowing data to be encoded in the temporal variations of light intensity that the camera can detect between successive line scans, while maintaining imperceptible flickering to human observers
Solution Approach 2:
The patent utilizes another dimension by exploiting the temporal dimension of the rolling shutter's sequential line scanning process. Instead of modulating the entire light source uniformly, it modulates different portions of the light signal corresponding to different scan lines at different times, effectively encoding data in the time dimension that the rolling shutter captures sequentially across the image sensor array
2Productivity
If the photo-detector image capture rate is increased to distinguish intensity transitions, then the data transmission rate is improved, but the device complexity and power consumption increase
Solution Approach 1:
The patent employs the rolling shutter mechanism as an intermediary that bridges between the light source modulation and the camera's frame capture. The rolling shutter's sequential line-by-line scanning process acts as a time-division multiplexer, allowing the camera to effectively sample the modulated light signal at a much higher effective rate than its frame rate would suggest, without requiring the camera hardware to operate at higher speeds
Solution Approach 2:
The patent applies dynamics by utilizing the rolling shutter's dynamic, time-varying exposure pattern across different scan lines. Each scan line is exposed at a different time, creating a dynamic sampling pattern that naturally captures the temporal variations in light intensity caused by modulation, converting a static frame-rate limitation into a dynamic time-division sampling advantage
3Use of energy by moving object
If the radiation source power is reduced to save energy in portable devices, then the power consumption is reduced, but the data transmission capabilities deteriorate
Solution Approach 1:
The patent uses periodic modulation of the light source at rates synchronized with the rolling shutter scan rate, allowing efficient encoding of data in the temporal domain. This enables effective communication using lower average optical power because the detection relies on temporal variations rather than requiring high signal intensity, thus reducing power consumption while maintaining data transmission capabilities
Solution Approach 2:
The patent changes the detection parameter from relying on absolute light intensity levels to relying on temporal variations in light intensity. By detecting changes in light intensity over time rather than absolute levels, the system can operate with lower average power while maintaining sufficient signal-to-noise ratio for reliable data detection, effectively changing the operational parameter regime
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 enhances data transmission rates, maintains low flickering, and reduces power consumption by effectively utilizing common apparatus like digital cameras and portable devices for visible light communications, improving bit error rate performance and bandwidth efficiency.
Implementation Method 1
A photo-detector can then be used to receive the time-modulated signal which is decoded to reveal the data that was transmitted by the light source
Data Source
AI summary
A transmission system for transmitting data as part of a communications system, the data comprising a plurality of data symbols or elements, the transmission system being configured to divide the data into at least a first data portion and a second data portion, wherein the first data portion is communicated by transmitting signals in selected carrier channels, wherein the transmission system is configured to encode at least one data symbol or element by selecting a relative order of at least one first carrier channel having a first operational state and at least one second carrier channel having a second operational state.