Wireless Contention Window Adjustment for Unlicensed Band Efficiency
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Solution Overview
Problem
In wireless communication systems, particularly in next-generation radio access technologies like NR, there is a need to improve the efficiency of channel access in unlicensed bands to prevent interference and ensure fair coexistence with existing systems like WiFi, especially when multiple devices with varying bandwidth capabilities operate simultaneously.
Innovation Solution
A multi-beam based listen-before-talk (LBT) method and a contention window size adjustment scheme are proposed, where the base station and user equipment perform LBT while considering the time gap between LBT success and actual transmission, and adjust the contention window size based on feedback and bandwidth part overlap, to optimize channel access and minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LBT is performed for each beam in NR unlicensed band, then channel access efficiency is improved, but LBT time consumption increases
Solution Approach 1:
The patent divides the channel access process into two stages: first performing LBT for each beam individually to identify successful beams, then performing a second LBT only for the selected beams before transmission. This segmentation allows the system to evaluate multiple beams without requiring all beams to pass complete LBT procedures, reducing overall time consumption while maintaining access efficiency.
Solution Approach 2:
The patent applies partial LBT action by requiring LBT success only for a predetermined number of beams (e.g., at least one beam) rather than requiring all beams to pass LBT. This partial action approach enables the system to proceed with transmission based on sufficient beam selection, avoiding the excessive time consumption that would result from verifying all beams while still ensuring adequate channel access efficiency.
2Reliability
If contention window size is adjusted based on HARQ feedback, then communication reliability is improved, but system complexity increases
Solution Approach 1:
The patent implements feedback-based CWS adjustment by monitoring HARQ feedback information from user equipment and using this feedback to dynamically adjust the contention window size. When HARQ feedback indicates successful transmissions, the CWS is reduced to allow more frequent access opportunities; when failures occur, the CWS is increased to reduce collision probability. This feedback mechanism improves reliability while keeping the adjustment logic relatively simple.
Solution Approach 2:
The patent changes the CWS parameter dynamically based on channel conditions and HARQ feedback rather than using a fixed value. The CWS is adjusted within a predetermined range according to the number of successful LBT attempts and feedback information, allowing the system to adapt to varying communication conditions. This parameter adjustment approach improves reliability without requiring complex control mechanisms, as the changes are based on straightforward feedback counting and threshold comparison.
3Adaptability or versatility
If multiple BWPs with different bandwidth capabilities are supported, then adaptability is improved, but channel access fairness deteriorates
Solution Approach 1:
The patent applies local quality by configuring different LBT parameters and CWS values for different BWPs based on their specific bandwidth capabilities. Each BWP has tailored LBT settings that match its characteristics, allowing narrower BWPs to use more conservative access parameters while wider BWPs can utilize more aggressive settings. This localized parameter configuration enables the system to support multiple bandwidth capabilities while maintaining fair access patterns appropriate for each BWP type.
Data Source
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AI summary
The present disclosure suggests a method for adjusting the size of a contention window of a base station/terminal. The method is characterized in that data are transmitted to a terminal/base station via a frequency band in a bandwidth part of a terminal, the bandwidth part is a part of a carrier bandwidth configured for the terminal, feedback information on the data is received from the terminal/base station, the size of the contention window of the base station/terminal is adjusted based on the feedback information, the size of the contention window is in the range of a counter value used for CAP which is an operation for the base station/terminal to determine channel occupancy, the bandwidth part overlaps with a plurality of CAP bandwidths, and, if the frequency band in which the data are transmitted overlaps with the plurality of CAP bandwidths, the base station/terminal adjusts the size of the contention window for at least one of the plurality of CAP bandwidths.