Directional LBT Feedback for Hidden Node Interference
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Solution Overview
Problem
In wireless communication systems, particularly in Unlicensed Spectrum, the hidden node issue causes interference due to the inability of nodes to determine the direction of Listen Before Talk (LBT) and feedback LBT results effectively, leading to inefficiencies in channel occupancy determination and resource allocation.
Innovation Solution
A method where both transmitters and receivers perform LBT and feedback channel occupancy information, allowing for the determination of Rx parameters and resource groups, thereby reducing hidden node interference and optimizing resource usage through groupcast signaling and repeated channel sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LBT is performed without directional information, then channel access can be determined, but hidden node interference cannot be avoided
Solution Approach 1:
The patent introduces directional information as a new dimension to the traditional LBT process. Instead of only determining channel occupancy in the time-frequency domain, the system now also considers spatial direction by obtaining beamforming information and determining LBT directions. This dimensional extension allows nodes to identify hidden interferers by comparing spatial signatures, thereby resolving the hidden node problem while maintaining channel access determination.
Solution Approach 2:
The patent implements a feedback mechanism where receiver nodes feed back LBT results and channel occupancy information to transmitter nodes. This feedback includes not only whether the channel is clear but also directional information about detected signals. Through this feedback loop, nodes can adjust their transmission directions and avoid hidden node interference, improving overall system reliability.
2Loss of information
If both transmitters and receivers perform LBT, then channel occupancy information can be determined, but device complexity increases
Solution Approach 1:
The patent makes receiver nodes perform LBT operations in addition to their traditional reception function. By equipping receivers with LBT capabilities, the system achieves more complete channel occupancy information. The receiver's LBT results are then fed back to transmitters, enabling better interference avoidance. This multi-functional approach allows a single node to perform both reception and channel sensing tasks.
Solution Approach 2:
The system enables nodes to determine channel occupancy for themselves through their own LBT operations. Each node performs LBT independently and uses the results to make transmission decisions. This self-service approach reduces the need for centralized coordination and allows nodes to autonomously avoid hidden node interference based on their local observations.
3Object-affected harmful factors
If directional LBT is implemented, then hidden node issues can be addressed, but determination of LBT direction becomes complex
Solution Approach 1:
The patent performs preliminary actions by obtaining beamforming information and determining transmission directions before executing the LBT process. By pre-acquiring spatial configuration data and beamforming parameters, the system simplifies the subsequent directional LBT operation. Nodes can directly use these pre-determined directions for channel sensing without performing complex real-time spatial analysis during the LBT process.
Solution Approach 2:
The patent introduces beamforming information as an intermediary that facilitates directional LBT. Instead of directly performing complex spatial measurements during LBT, the system uses pre-computed beamforming parameters as intermediaries to guide the channel sensing process. This intermediary layer simplifies the determination of LBT directions by providing ready-made spatial reference information.
4Reliability
If frequency resources are occupied for LBT signaling, then channel sensing can be performed, but resource overhead increases
Solution Approach 1:
The patent merges the LBT signaling function with existing uplink control channel resources. Instead of allocating separate dedicated resources for LBT signaling, the system combines LBT result feedback with regular uplink control information transmissions. This merging approach allows LBT information to be conveyed using existing resource structures, reducing overall resource overhead while maintaining reliable LBT performance.
Data Source
AI summary
A first node receives a first signaling; performs a first channel sensing operation over a first subband; and transmits a first signal. The first signaling comprises first indication information, used for indicating an Rx parameter of the first channel sensing operation; the first channel sensing operation is used for determining channel occupancy information, the channel occupancy information used for determining whether the first subband can be used by a transmitter of the first signaling for signal transmission; the first signal is used for indicating the channel occupancy information. The receiver in communications is enabled to perform channel sensing and feedback results, hence a reduction in interferences incurred from hidden node issues.