Random Access and LBT Failure Recovery in 5G NR
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Solution Overview
Problem
Wireless communication systems face challenges in maintaining reliable connections in unlicensed or shared spectrum, particularly with beam failure and consistent listen-before-talk (LBT) failures, which affect data transmission and user experience.
Innovation Solution
The implementation of advanced beam management and LBT failure recovery mechanisms, including dynamic bandwidth part switching and random access processes, to ensure consistent communication in 5G NR and LTE technologies, allowing for efficient operation in unlicensed or shared spectrum environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If listen-before-talk (LBT) procedure is implemented in unlicensed spectrum, then channel access reliability is improved, but transmission delay increases due to consistent LBT failures
Solution Approach 1:
The patent applies preliminary action by performing beam failure recovery before initiating random access procedure. The UE first attempts to recover from beam failure using dedicated recovery resources, and only if that fails does it proceed to random access. This preliminary recovery attempt reduces the overall transmission delay by resolving beam issues before channel access becomes necessary.
Solution Approach 2:
The patent implements dynamic behavior by making the random access procedure conditional rather than static. The UE dynamically determines whether to perform random access based on the outcome of beam failure recovery - it performs random access only when beam failure recovery fails. This dynamic adaptation optimizes channel access reliability while minimizing unnecessary transmission delays.
2Reliability
If random access procedure is performed after beam failure recovery, then connection reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the failure recovery process into distinct stages: first beam failure recovery using dedicated resources, then random access procedure using common resources if the first stage fails. This segmentation allows each procedure to be optimized independently and simplifies the overall control logic by creating clear decision boundaries between different recovery mechanisms.
Solution Approach 2:
The patent uses beam failure recovery as an intermediary step between beam failure detection and random access procedure. This intermediary mechanism provides a dedicated recovery path that can resolve many beam issues without requiring the more complex random access procedure, thereby reducing overall device complexity while maintaining connection reliability.
3Productivity
If dedicated physical uplink control channel (PUCCH) resources are used for beam failure recovery, then recovery efficiency is improved, but resource allocation complexity increases
Solution Approach 1:
The patent applies local quality by allocating dedicated PUCCH resources specifically for beam failure recovery purposes, rather than using general-purpose uplink resources. This dedicated allocation optimizes the recovery process by providing guaranteed resources with appropriate characteristics for beam failure reporting, while the complexity is managed through clear resource partitioning rules that simplify overall resource management.
Data Source
AI summary
A base station transmits first random access parameters, associated with beam failure recovery, and second random access parameters. The base station may receive, in response to a beam failure on a primary cell and based on the first random access parameters, a first random access preamble on a first BWP of the primary cell. The base station may receive, based on the second random access parameters and for consistent LBT failure recovery, a second random access preamble on a second BWP of the primary cell. Receiving the second random access preamble may be in response to stopping of a first random access process and switching of an active BWP of the primary cell from the first BWP to a second BWP. The stopping and the switching may be based on consistent LBT failure for the primary cell.