Visible Light Communication for Mass Transit Vehicles
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Solution Overview
Problem
Current communication systems for mass transit vehicles face challenges such as large-scale and non-stationary fading, fast handover, high penetration losses, limited visibility in tunnels, harsh electromagnetic environments, and imbalanced uplink and downlink in RF systems, leading to spotty coverage and high signaling overhead, especially at speeds exceeding 250 km/h.
Innovation Solution
A visible light communication system is implemented using a series of light sources and photodetectors placed on the mass transit vehicle and the track, establishing bidirectional one-to-one communication channels with symmetric placement to enhance bandwidth and reduce interference, utilizing light emitting diodes for efficient data modulation and synchronization through velocity acceleration estimation units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If visible light communication is implemented using series of light sources and photodetectors, then data transmission rate is improved to ultra-high speeds (Tbit/s), but device complexity increases due to the need for multiple components and precise alignment
Solution Approach 1:
The communication system is divided into multiple independent light sources and photodetectors arranged in series along the track and vehicle. Each light source-photodetector pair forms an independent communication channel, allowing parallel data transmission and achieving ultra-high data rates while maintaining manageable complexity through modular architecture
Solution Approach 2:
The patent transitions from traditional RF communication in the electromagnetic spectrum to visible light communication, utilizing a different dimension of the electromagnetic spectrum. This enables ultra-high data rates by exploiting the higher frequency and bandwidth of visible light, while the linear arrangement of components along the track-vehicle interface simplifies the spatial complexity
2Reliability
If light sources and photodetectors are placed on moving vehicle and track, then communication reliability is improved by eliminating RF radiation effects, but measurement precision deteriorates due to challenges in maintaining precise alignment at high speeds
Solution Approach 1:
The system is designed to dynamically adapt to the relative motion between the vehicle and track. The light sources and photodetectors are arranged in series along the direction of motion, creating multiple overlapping communication channels that maintain alignment through the natural geometry of the moving interface, eliminating the need for complex active alignment systems
Solution Approach 2:
The patent uses the physical interface between the moving vehicle and stationary track as an intermediary structure. By placing light sources and photodetectors at this interface point, the system naturally maintains alignment through the mechanical constraints of the track-vehicle geometry, while eliminating RF radiation effects that plague traditional wireless communication systems
3Productivity
If symmetric placement of light sources and photodetectors is used, then bandwidth is improved through multiple communication channels, but manufacturing precision requirements increase due to stringent alignment tolerances
Solution Approach 1:
The symmetric placement creates multiple segmented communication channels, with light sources and photodetectors arranged in corresponding series on both the vehicle and track. This segmentation allows each channel to operate independently with relaxed individual tolerances, while the collective array achieves high total bandwidth through parallel transmission
Solution Approach 2:
The patent employs homogeneous symmetric placement patterns for light sources and photodetectors, where identical components are arranged in matching series on both the moving and stationary sides. This homogeneity simplifies manufacturing by using standardized components and uniform spacing, reducing the impact of alignment tolerances through statistical averaging across multiple channels
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 system provides ultra-high data rates (Tbit/s) for both uplink and downlink communications without RF radiation effects, offering continuous and efficient data transfer with significantly lower costs compared to existing technologies.
Implementation Method 1
a series of light sources (4) placed either on a base (5) of the mass transit vehicle (2), or in proximity of the base (5) of the mass transit vehicle (2), or on the track (3), or in proximity of the track (3), and a series of photodetectors (6) placed either on a base (5) of the mass transit vehicle (2), or in proximity of the base (5) of the mass transit vehicle (2), or on the track (3), or in proximity of the track (3), wherein each of the light source (4) is adapted to establish one-to-one visible light communication channel (7) with each of the photodetectors (6)
Data Source
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AI summary
A system (1) of visible light communication for a mass transit vehicle (2), wherein the mass transit vehicle (2) is adapted to run on a track (3), the system comprising a series of light source (4) placed either on a base (5) of the mass transit vehicle (2), or in proximity of the base (5) of the mass transit vehicle (2), or on the track (3), or in proximity of the track (3), and a series of photodetectors (6) placed either on the base (5) of the mass transit vehicle (2), or in proximity of the base (5) of the mass transit vehicle (2), or on the track (3), or in proximity of the track (3), wherein each of the light source (4) is adapted to establish one-to-one visible light communication channel (7) with each of the photodetectors (6) at a time stamp, such that a data being carried by light from the light sources (4) at the time stamp is transferred to the photodetectors (6) for further communication of data either into the mass transit vehicle (2) or out of the mass transit vehicle (2).