Sensing Beam Selection for LBT in Unlicensed mmWave 5G
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Solution Overview
Problem
In wireless communication systems, particularly in unlicensed high-frequency bands like millimeter wave frequencies, the challenge lies in determining a suitable sensing beam for directional listen-before-talk (LBT) procedures when the receive (Rx) and transmit (Tx) beams are mismatched, as the beam patterns used for channel sensing differ from those for directional transmission, leading to inefficiencies in channel access.
Innovation Solution
The proposed solution involves determining a suitable sensing beam by finding an Rx beam that meets specific criteria, such as having energy equal to or greater than a product of the weight factor and energy of each Tx beam, where the weight factor considers peak gains and antenna array configurations, allowing the Rx beam to function as a proxy for the Tx beams during LBT procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a directional beam is used for transmission in unlicensed high-frequency bands, then transmission efficiency is improved, but channel sensing accuracy deteriorates because the sensing beam pattern differs from the transmission beam pattern
Solution Approach 1:
The patent uses a receive (Rx) beam as a copy or proxy for the transmit (Tx) beam pattern during channel sensing. Instead of using the actual Tx beam for sensing, the system identifies an Rx beam that matches the Tx beam pattern characteristics, allowing accurate channel sensing without directly using the transmission beam itself. This copying approach resolves the contradiction by enabling accurate sensing through a surrogate beam pattern.
Solution Approach 2:
The patent introduces an intermediate Rx beam as a mediator between the Tx beam and the channel sensing process. The Rx beam serves as an intermediary element that allows the system to sense the channel accurately without requiring the Tx beam itself to be used for sensing. This mediator approach enables the system to maintain both transmission efficiency and sensing accuracy by decoupling the sensing function from the transmission function.
2Adaptability or versatility
If multiple beams are used for transmission within a transmission opportunity, then transmission versatility is improved, but LBT procedure complexity increases due to the need to sense each beam separately
Solution Approach 1:
The patent merges multiple beam sensing operations into a single unified LBT procedure. Instead of performing separate sensing operations for each Tx beam, the system identifies a single matching Rx beam that can represent multiple Tx beams and performs one sensing operation. This merging approach maintains transmission versatility while significantly reducing LBT procedure complexity by eliminating redundant sensing steps.
Solution Approach 2:
The patent makes the identified Rx beam universal for sensing multiple different Tx beams. A single Rx beam pattern is used to sense channels for multiple transmission beams, allowing the system to maintain versatility in using multiple Tx beams while simplifying the sensing process. This multi-functionality approach enables one Rx beam to serve multiple sensing purposes, reducing overall system complexity.
Data Source
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AI summary
For unlicensed high-frequency bands such as mmW bands as used in 5G NR communications, either by regulation or for coexistence with licensed frequency bands, there may be a need for a contention-based access procedure such as the LBT procedure. A challenge is to find a suitable sensing beam to functions as a proxy for a set of transmission beams. In an aspect of the disclosure, a method and an apparatus are provided. The apparatus is configured to determine a set of transmission beams for a transmission opportunity, determine a sensing beam for the set of transmission beams based on a set of beam sensing criteria; and initiate an LBT procedure by sensing an energy on the determined sensing beam. The apparatus may then use the LBT procedure to obtain the access to and transmit data on the determined set of transmission beams.