Optical Signal Retransmission for Hidden Node Collision Avoidance
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Solution Overview
Problem
Optical wireless communication systems face challenges in collision avoidance due to the directional nature of optical transmitters and receivers, leading to hidden node problems and increased latency in channel sensing, which can result in reduced downlink efficiency and higher collision probabilities.
Innovation Solution
A transceiver apparatus with a multiplexer arrangement and controller that processes and retransmits optical wireless signals, indicating channel occupancy by retransmitting part of the received signal to other devices, allowing for efficient collision avoidance and reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If channel sensing procedures are implemented in optical wireless communication systems, then collision probability can be reduced, but latency increases due to the need to decode packets before transmitting busy signals
Solution Approach 1:
The system transmits a busy signal immediately upon receiving a packet, before the packet is fully decoded. This preliminary action indicates channel occupancy to other stations without waiting for complete packet processing, thereby reducing latency while maintaining collision avoidance effectiveness
Solution Approach 2:
The invention extracts only the essential information needed for collision avoidance (channel occupancy indication) from the received packet, rather than requiring full packet decoding. This is achieved by transmitting a busy signal based on partial reception of the packet, separating the collision avoidance function from the complete packet processing function
2Reliability
If medium busy signals are used to indicate channel occupancy, then collision avoidance is improved, but downlink efficiency decreases due to high latency in signal transmission
Solution Approach 1:
The busy signal is transmitted preliminarily and immediately upon packet reception, before any decoding or processing occurs. This eliminates the time delay that would otherwise prevent downlink transmissions, allowing the AP to maintain high downlink efficiency while still providing collision avoidance functionality
Solution Approach 2:
The system segments the packet processing function from the channel occupancy indication function. The busy signal transmission is separated from the packet decoding process, allowing these two operations to occur in parallel or independently, thereby preventing the decoding process from becoming a bottleneck for downlink efficiency
3Measurement precision
If packet decoding is performed before transmitting busy signals, then accurate channel occupancy indication is achieved, but latency and processing time increase
Solution Approach 1:
The system performs partial packet reception and transmission of the busy signal before complete packet decoding is finished. This partial action is sufficient to indicate channel occupancy to other stations, reducing processing time while maintaining adequate accuracy for collision avoidance purposes
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
The solution effectively reduces collisions and latency in optical wireless communication systems by providing a mechanism for devices to detect channel occupancy, enhancing network performance and efficiency.
Implementation Method 1
a receiver for receiving light (optionally of a first wavelength or range of wavelengths) representing optical wireless communication signals transmitted by the further devices
Implementation Method 2
a transmitter for transmitting further light (optionally of a second wavelength or range of wavelengths) representing optical wireless communication signals
Data Source
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AI summary
An optical wireless communication (OWC) system comprising: a first device comprising a transceiver apparatus; and a plurality of further devices each comprising a respective further transceiver apparatus, wherein the first device is configured to communicate via an optical channel with the plurality of further devices, and wherein the transceiver apparatus of the first device comprises: a receiver for receiving light representing optical wireless communication signals transmitted by the further devices, the receiver comprising a photodetector; receiver-side processing circuitry for processing optical wireless communication signals received by the receiver to extract data represented by the received optical wireless communication signals; a transmitter for transmitting further light representing optical wireless communication signals; transmitter-side processing circuitry for producing optical wireless communication signals for transmission by the transmitter; and at least one optical component for at least one of reflecting or guiding at least some light received from at least one of the further devices towards at least one of the further devices.