Directional Listen-Before-Talk with Beam Shrinking for Faster Channel Access
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Solution Overview
Problem
Wireless devices in unlicensed radio frequency spectrum bands face significant latency due to directional interference during contention-based channel access, as existing listen-before-talk (LBT) procedures are inefficient in managing beamforming transmissions.
Innovation Solution
Implementing directional LBT schemes such as beam-shrinking and beam sweeping to mitigate interference by switching or narrowing beams based on interference detection, adjusting parameters like counter values and contention windows, and performing concurrent LBT across multiple narrow beams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If directional beamforming is used for transmissions, then communication efficiency is improved, but interference from other directions increases channel access latency
Solution Approach 1:
The channel access procedure is segmented into multiple directional clear channel assessment (CCA) attempts, each using a different beam direction. Instead of using a single wide beam for CCA, the device divides the assessment into multiple narrow beam directions, allowing it to find an interference-free direction more efficiently and reduce overall access latency.
Solution Approach 2:
The beam direction and width used for CCA are made dynamic rather than static. The device adapts the CCA beam direction based on detected interference patterns, switching between different beam directions to find clear channels. This dynamic adaptation allows the system to respond to changing interference conditions and minimize access latency.
2Area of stationary object
If wide beams are used for clear channel assessment, then coverage area is improved, but interference detection accuracy decreases
Solution Approach 1:
The wide coverage area is segmented into multiple narrow beam directions for CCA. Each narrow beam provides precise interference detection in its specific direction, while collectively covering the same overall area as the wide beam would provide, thus maintaining coverage while improving detection accuracy.
Solution Approach 2:
Different beam directions are used for CCA in different spatial locations or directions. Each narrow beam provides high-quality, precise interference detection for its specific directional sector, rather than using a single wide beam that provides lower-quality detection across all directions simultaneously.
3Reliability
If multiple narrow beams are used for concurrent LBT, then interference mitigation is improved, but device complexity increases
Solution Approach 1:
The single CCA process is segmented into multiple parallel directional CCA operations, each using a different narrow beam. This segmentation allows interference mitigation in each direction while the overall complexity is managed by reusing the same CCA logic and counter mechanisms across different beam directions.
Solution Approach 2:
The same CCA logic and counter mechanism are made multi-functional by applying them to multiple different beam directions. Rather than creating separate complex systems for each beam, a universal CCA procedure is designed that can operate with any beam direction, reducing overall device complexity while maintaining interference mitigation capabilities.
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. Wireless devices operating in an unlicensed radio frequency spectrum band may perform directional listen-before-talk (LBT) procedures to gain access to a channel. In a beam-shrinking scheme for directional LBT, a wireless device may start an LBT procedure using a first beam (e.g., a wide beam). If the clear channel assessment (CCA) fails for the first beam, the device may switch the LBT procedure to a second (e.g., narrower) beam. Depending on the direction of the interference source, the second beam may result in a successful LBT procedure. In a beam sweeping scheme for directional LBT, a wireless device may perform concurrent LBT over multiple narrow beams. If any beam of the set of beams detects frequent or continuous interference, the device may drop that beam from the concurrent LBT procedure.