NR-U Channel Access via Type 2D LBT and CP Extension
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently utilizing unlicensed spectrum for New Radio (NR) operations, particularly in maintaining fair coexistence with other technologies and reducing the complexity of listen-before-talk (LBT) procedures, especially in the 5 GHz band.
Innovation Solution
The introduction of a new 25 us LBT type with a 9 us measurement window and the definition of a new channel access procedure, Type 2D, which allows for immediate transmission after sensing the channel to be idle for at least 25 us, along with cyclic prefix (CP) extensions and adjustments for configured grant operations, to optimize channel access and data transmission in unlicensed spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional LBT procedures are used in unlicensed spectrum, then fair coexistence with other technologies is maintained, but channel access complexity and latency increase
Solution Approach 1:
The LBT procedure is segmented into different types (Type 1, Type 2A, Type 2B, Type 2C, Type 2D) with varying sensing durations and measurement windows. Type 2D LBT segments the sensing process into a 25 us sensing interval with a 9 us measurement window, allowing faster channel access while maintaining coexistence through appropriate sensing duration selection based on channel conditions and traffic priorities.
Solution Approach 2:
The patent introduces dynamic LBT type selection where the system can switch between different LBT types (1, 2A, 2B, 2C, 2D) based on real-time channel conditions, traffic priority, and coexistence requirements. This dynamic adaptation allows the system to optimize between fairness and access speed by selecting the appropriate LBT type for each transmission opportunity.
2Measurement precision
If longer sensing intervals are used for channel access, then channel availability is more accurately determined, but transmission latency increases
Solution Approach 1:
The patent changes the sensing interval parameter from traditional longer durations to a optimized 25 us sensing interval with 9 us measurement window for Type 2D LBT. This parameter optimization maintains sufficient channel detection accuracy while reducing access latency. The system can further adjust sensing duration parameters based on channel conditions, traffic priority, and coexistence requirements.
Solution Approach 2:
Instead of performing full traditional LBT sensing procedures, Type 2D LBT performs a partial sensing action with a shortened 25 us interval and 9 us measurement window. This partial sensing is sufficient for many unlicensed spectrum scenarios and provides a good trade-off between detection accuracy and access speed, allowing faster channel access when conditions permit.
3Speed
If immediate transmission is enabled after short sensing, then channel access speed increases, but coexistence fairness with other technologies may be compromised
Solution Approach 1:
The system dynamically selects between multiple LBT types (1, 2A, 2B, 2C, 2D) with different sensing durations and immediate transmission capabilities. Type 2D enables immediate transmission after 25 us sensing for speed, while other types provide longer sensing for fairness. The dynamic selection based on channel conditions and traffic priority resolves the contradiction by adapting the trade-off point in real-time.
Solution Approach 2:
Different LBT types with different sensing durations and immediate transmission characteristics are applied locally based on specific channel conditions, traffic priority, and coexistence requirements. High-priority traffic may use Type 2D with immediate transmission, while other traffic uses more conservative types, allowing each transmission to have optimized local characteristics rather than a uniform approach.
4Reliability
If cyclic prefix extensions are applied for configured grant operations, then uplink transmission reliability improves, but processing complexity increases
Solution Approach 1:
Cyclic prefix extensions are pre-configured and applied to uplink transmissions in advance, particularly for configured grant operations. The extended cyclic prefix is prepared beforehand to accommodate timing variations and channel conditions, improving uplink reliability without requiring complex real-time processing during actual transmission.
Data Source
AI summary
Various embodiments herein provide techniques for wireless communication on New Radio unlicensed (NR-U) spectrum. For example, embodiments include techniques for a new listen-before-talk type and associated measurement window. Additionally, embodiments include techniques for determination of a cyclic prefix (CP) extension for an uplink transmission, such as a configured grant transmission or a dynamically scheduled transmission. Other embodiments may be described and claimed.