Adaptive Cyclic Prefix Extension for LBT-Blocked Sidelink Access
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Solution Overview
Problem
In wireless communication systems, particularly in 5G networks using sidelink communications over unlicensed bands (SL-U), the existing cyclic prefix extension (CPE) mechanism for avoiding collisions among user equipment (UEs) is inefficient as it does not guarantee protection for subsequent transmissions, leading to resource wastage and potential collisions.
Innovation Solution
A UE adjusts its CPE based on listen before talk (LBT) outcomes, increasing the CPE when LBT blocking occurs and decreasing it when not blocked, using linear or non-linear step sizes, and obtaining parameters from a sensing server or other UEs to optimize channel access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE selects a longer CPE to gain priority for channel access, then channel access reliability is improved, but resource wastage increases due to consuming resources without actual data transmission
Solution Approach 1:
The CPE length is made dynamic rather than static. The UE adjusts the CPE length based on LBT outcomes and channel conditions, selecting from multiple configured CPE lengths. This allows the system to adapt CPE duration to actual needs, maintaining reliability when necessary while reducing waste when the channel is clear.
Solution Approach 2:
The CPE parameter (length/duration) is changed based on operational conditions. The network configures multiple CPE lengths and the UE selects appropriate lengths based on LBT blocking detection and channel availability, optimizing the balance between access reliability and resource efficiency.
2Device complexity
If a UE uses a fixed CPE length for channel access, then device complexity is reduced, but adaptability to varying channel conditions deteriorates
Solution Approach 1:
The system transitions from fixed CPE to dynamic CPE adjustment. The UE monitors LBT outcomes and channel conditions, then adapts CPE length accordingly. This provides adaptability to varying channel conditions while maintaining manageable complexity through network-configured parameters and standardized adjustment rules.
Solution Approach 2:
The UE uses feedback from LBT procedures and channel sensing to adjust CPE length. By detecting LBT blocking and channel availability, the system dynamically selects appropriate CPE lengths, enabling adaptability while following network-provided guidelines that control complexity.
3Reliability
If a UE increases CPE to ensure transmission protection, then collision avoidance is improved, but resource efficiency deteriorates due to extended transmission time without data
Solution Approach 1:
CPE length is dynamically adjusted based on actual channel conditions and LBT outcomes. The UE uses longer CPE when collision risk is detected and shorter CPE when the channel is clear, maintaining collision avoidance capability while improving resource efficiency by avoiding unnecessarily long CPE extensions.
Solution Approach 2:
The CPE parameter is changed based on operational needs. The network configures multiple CPE lengths and the UE selects appropriate lengths based on LBT blocking detection, ensuring collision avoidance when necessary while maintaining resource efficiency through parameter optimization.
4Productivity
If a UE decreases CPE to save resources, then resource efficiency is improved, but collision protection capability deteriorates
Solution Approach 1:
The system dynamically adjusts CPE length based on real-time channel conditions and LBT outcomes. When collision risk is detected, the UE increases CPE length for protection; when the channel is clear, the UE decreases CPE length to save resources, achieving both resource efficiency and collision protection as needed.
Solution Approach 2:
The CPE parameter is optimized by changing its length based on operational conditions. The UE selects from network-configured CPE lengths according to LBT blocking detection and channel availability, ensuring adequate collision protection when necessary while maximizing resource efficiency through parameter optimization.
Data Source
AI summary
An example user equipment (UE) device for wireless communication includes a communication interface; and one or more processors coupled to the communication interface, wherein the one or more processors are configured to: select a first cyclic prefix extension (CPE) for a transmission over a shared sidelink band via the communication interface; perform a listen before talk (LBT) procedure on the shared sidelink band; in response to the LBT procedure, determine that the shared sidelink band is LBT-blocked; in response to the shared sidelink band being LBT-blocked, select a second CPE larger than the first CPE; and transmit the second CPE and the transmission over the shared sidelink band via the communication interface.