Uplink Channel Access Using LBT Subsets to Cut NR-U Delay
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Solution Overview
Problem
The challenge of ensuring robust coexistence of LTE and NR technologies in unlicensed frequency bands while minimizing interference with existing wireless communication devices and maintaining communication quality is unresolved.
Innovation Solution
A method for uplink transmission in a wireless communication system involving configured grant (CG) and scheduled transmissions using Listen Before Talk (LBT) bandwidth subsets, with channel access through a variable contention window, ensuring continuous resource allocation and immediate transition between transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Listen Before Talk (LBT) channel access procedure is used in unlicensed bands, then coexistence with existing wireless devices is improved, but transmission delay and resource allocation complexity increase
Solution Approach 1:
The bandwidth is divided into multiple LBT bandwidth subsets, each independently managed for channel access. This segmentation allows parallel channel access attempts across different frequency resources, reducing overall transmission delay while maintaining coexistence through distributed LBT procedures
Solution Approach 2:
Channel access procedures are initiated in advance for multiple bandwidth subsets before actual data transmission. The system performs preliminary LBT checks and prepares transmission resources ahead of time, reducing waiting delays while ensuring fair coexistence with other devices
2Reliability
If random backoff with variable contention window is used for channel access, then collision avoidance is improved, but channel access time and transmission latency increase
Solution Approach 1:
The contention window backoff procedure is applied independently to multiple bandwidth subsets rather than a single wide bandwidth. This segmentation allows devices to attempt channel access in parallel across different frequency resources, reducing overall channel access time while maintaining collision avoidance through distributed backoff mechanisms
Solution Approach 2:
The system dynamically selects which bandwidth subsets to access based on channel conditions, traffic requirements, and backoff outcomes. This dynamic adaptation allows the system to optimize between collision avoidance and access speed by flexibly adjusting channel access strategies in real-time
3Productivity
If configured grant and scheduled transmissions are performed on continuous resources, then spectral efficiency is improved, but interference management complexity and signal processing load increase
Solution Approach 1:
The continuous frequency resources are divided into multiple LBT bandwidth subsets for independent management and transmission. This segmentation reduces interference management complexity by allowing localized processing and independent channel access decisions for each subset, while maintaining high spectral efficiency through continuous resource utilization across all subsets
Data Source
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AI summary
A method for receiving downlink transmission by a terminal comprises the steps of: performing uplink transmission, which is related to channel occupancy shared between a base station and the terminal, to the base station; and receiving, from the base station, downlink transmission performed after a gap from a time point at which the base station has received the uplink transmission, wherein the downlink transmission is performed on the basis of channel access performed by the base station, the channel access is performed on the basis of the gap, and information included in the downlink transmission and a resource through which the downlink transmission is performed are determined on the basis of whether the base station has configured, for the terminal, a threshold value of energy detection for the channel occupancy.