Reuse-One Channel Access for New Radio in Unlicensed Spectrum
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Solution Overview
Problem
New radio (NR) wireless communication systems face challenges in efficiently accessing unlicensed spectrum due to the limitations of listen-before-talk (LBT) mechanisms, which hinder reuse-one channel access, leading to degraded system performance when co-existing with Wi-Fi and other technologies.
Innovation Solution
An enhanced LBT design is implemented, allowing NR base stations to perform cooperative channel access by grouping into reuse-one clusters, using category 4 and category 2 LBT procedures to manage channel occupancy times, enabling cooperative competition for bandwidth and improving coexistence with legacy NR-U, LAA, and Wi-Fi technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional LBT mechanisms are used for channel access in unlicensed spectrum, then coexistence with Wi-Fi and other technologies is maintained, but system performance is degraded and reuse-one channel access is hindered
Solution Approach 1:
The channel access procedure is segmented into two distinct categories: Category 4 LBT for initial channel acquisition with full random backoff, and Category 2 LBT for subsequent channel access within the same COT with simplified listen-before-talk. This segmentation allows NR base stations to efficiently reuse the channel while maintaining fair coexistence with Wi-Fi and other LBT-based systems.
Solution Approach 2:
The system dynamically transitions between Category 4 and Category 2 LBT procedures based on channel occupancy status. When a base station successfully acquires the channel through Category 4 LBT, it enters a COT where subsequent accesses use the more efficient Category 2 procedure. This dynamic adaptation optimizes system performance while preserving coexistence requirements.
2Ease of operation
If NR base stations perform independent channel access, then individual channel acquisition is possible, but reuse-one channel access is hindered and coexistence performance degrades
Solution Approach 1:
Multiple NR base stations are merged into a coordinated COT structure where one base station acts as the leading station that performs Category 4 LBT and announces the COT. Other base stations (non-leading) then perform Category 2 LBT within the announced COT. This merging enables reuse-one channel access where multiple base stations can transmit simultaneously on the same time-frequency resources while maintaining proper coexistence behavior.
3Reliability
If Category 4 LBT is used for all channel access attempts, then fair channel access is ensured, but channel occupancy time is reduced and system efficiency decreases
Solution Approach 1:
The leading base station performs the comprehensive Category 4 LBT procedure in advance to acquire the channel and establish a COT. This preliminary action creates a reserved time window where non-leading base stations can access the channel using the faster Category 2 procedure without performing full Category 4 LBT. This approach ensures fair initial channel access while extending the effective channel occupancy time for the group of base stations.
Solution Approach 2:
The COT announcement serves as an intermediary mechanism that mediates between the fair access requirements of Category 4 LBT and the efficiency needs of repeated channel access. The leading base station's COT announcement allows non-leading base stations to bypass the time-consuming Category 4 procedure and directly use Category 2 LBT, thereby extending channel occupancy while maintaining fairness through the initial Category 4 access.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques for reuse one channel access for new radio communications in unlicensed spectrum. A method that may be performed by a first base station (BS) includes occupying a bandwidth, based on a category 4 (CAT4) listen before talk (LBT) procedure on the bandwidth, wherein the CAT4 LBT procedure is based on a first contention window (CW); arranging a category 2 (CAT2) LBT occasion for the bandwidth during a channel occupancy time (COT) for the bandwidth; and receiving an indication that at least a second BS has occupied the bandwidth during the CAT2 LBT occasion.