VLC Dimming Method Using Multi-Pulse Pulse-Position Modulation
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Solution Overview
Problem
Traditional modulation schemes in visible light communication (VLC) do not effectively maximize data transmission while maintaining desired light intensity, especially during dimming operations, leading to inefficiencies in data transfer and spectral utilization.
Innovation Solution
A VLC device determines n time slots and w pulses based on a dimming value and normalized transmission rate, using multi-pulse pulse-position modulation (MPPM) to optimize light intensity and data transmission, with codewords designed to maximize Hamming distance and minimize pairs with minimum Hamming distance for efficient data encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional modulation schemes (PPM, VPPM) are used in VLC, then the system is simple to implement, but data transmission efficiency and spectral utilization are not maximized
Solution Approach 1:
The patent changes the modulation parameters by using MPPM with variable number of pulses (w) and time slots (n) based on dimming values. Instead of fixed parameters, the system dynamically adjusts w and n to maximize normalized transmission rate while maintaining desired light intensity, thereby improving data transmission efficiency without excessive complexity increase
Solution Approach 2:
The patent introduces dynamic adaptation by adjusting modulation parameters (w and n) according to dimming values and channel conditions. The system dynamically selects optimal parameter combinations to maximize transmission efficiency under varying operational conditions, moving from static traditional schemes to adaptive modulation
2Illumination intensity
If dimming control is applied to control light intensity in VLC, then light intensity is precisely controlled, but data transmission rate decreases
Solution Approach 1:
The patent resolves this contradiction by changing the relationship between dimming value and transmission rate. Instead of a fixed inverse relationship, the system uses multiple codewords with different weights (w) corresponding to different dimming levels. By selecting optimal codeword combinations, the system maintains precise light intensity control while maximizing the normalized transmission rate at each dimming level
Solution Approach 2:
The patent applies partial action by transmitting only w pulses out of n available time slots. This partial transmission approach allows the system to control light intensity (by adjusting w/n ratio) while still achieving high transmission efficiency through optimized pulse positioning and codeword selection
3Reliability
If codewords are designed to maximize Hamming distance, then error detection and correction capability is improved, but codebook complexity increases
Solution Approach 1:
The patent manages codebook complexity by parameterizing the codebook generation process. Instead of storing all possible codewords, the system generates codewords on-demand using mathematical relationships between dimming values, time slots (n), and pulses (w). This parameter-based approach maintains high Hamming distance for error detection while avoiding the storage complexity of exhaustive codebooks
Data Source
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AI summary
A method implemented by a visible light communication (VLC) device comprises determining, by a processor of the VLC device, n time slots for a signal block based on a dimming value, the signal block specifying a predetermined duration of time and the signal block being divided equally into n time slots, with the dimming value specifying a light intensity of light to be emitted by the light source, determining, by the processor, w pulses to be transmitted during one or more of the n time slots of the signal block, based on the dimming value and according to a pulse pattern indicating a position of the w pulses transmitted during the one or more of the n time slots, and determining, by the processor, a codeword based on n and w, the codeword corresponding to the pulse pattern.