Straylight-Based Channel Access for Optical Wireless Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Optical wireless communication (OWC) systems face the 'hidden node problem' where nodes with parallel optical frontends cannot communicate with each other, leading to interference and reduced throughput due to simultaneous data transmissions on the same wavelength channel.
Innovation Solution
Incorporating a detector and discriminator to monitor straylight signals for channel occupancy, allowing for the generation and detection of a dedicated signal component that indicates channel occupancy, enabling coordinated channel access and reducing interference between neighboring OWC devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If OWC nodes transmit using intensity modulation on the same broad wavelength light channel, then data transfer speed and bandwidth are improved, but interference between neighboring nodes increases due to the hidden node problem
Solution Approach 1:
The patent applies preliminary action by implementing a listen-before-talk mechanism where OWC nodes monitor the light channel for a predetermined period before transmitting data. This preliminary monitoring action allows nodes to detect ongoing transmissions and avoid initiating new transmissions that would cause interference, thereby resolving the hidden node problem while maintaining high data transfer speeds through intensity modulation
2Productivity
If multiple ED units send data packets to the AP simultaneously, then channel utilization is improved, but packet loss increases due to interference
Solution Approach 1:
The patent implements feedback through a monitoring mechanism where OWC nodes continuously observe the light channel during a predetermined time period before transmission. This feedback loop provides real-time information about channel occupancy, allowing nodes to adjust their transmission timing and avoid simultaneous transmissions that would cause interference and packet loss, thereby maintaining both high channel utilization and reliable packet delivery
3Ease of operation
If OWC nodes use fixed wide spectrum light detectors, then detection simplicity is improved, but ability to avoid interfering transmissions is reduced compared to selective channel reception
Solution Approach 1:
The patent combines preliminary action with simple detection by requiring OWC nodes to monitor the light channel for a predetermined period before transmission. This preliminary monitoring action, performed by simple wide spectrum detectors, provides enough information to avoid interfering transmissions without requiring complex selective channel reception capabilities, thus maintaining both detection simplicity and the ability to avoid interference
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 solution effectively mitigates the hidden node problem by allowing OWC devices to detect channel occupancy without complex digital demodulation, enhancing channel access and reducing interference, thereby improving communication quality and throughput.
Implementation Method 1
a detector for detecting a straylight signal
Data Source
AI summary
This invention relates to an optical wireless communication (OWC) system that is configured to make use of observations of straylight reflections as generated by an OWC transmitter in order to support contention-based channel access including that of multiple basic or extended service sets (BSS, ESS) with overlapping coverage areas. It is proposed to have an additional optical signal or signal component generated in the OWC transmitter which allows for simple detection without having to do heavy digital demodulation processing. A learning phase may allow to adjust for environmental conditions like reflectivity or transmitter characteristics.