PUCCH Beam Recovery Using Default Spatial Relation After Failure
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Solution Overview
Problem
Existing communication systems lack a mechanism to recover transmission beams for uplink channels when beam failure occurs, particularly for physical uplink control channels (PUCCH), as there is no reference signal available during such failures.
Innovation Solution
A method involving a user equipment (UE) that detects beam failure, initiates a contention-based random-access channel (RACH), transmits a medium access control (MAC) control element (CE), and determines a default transmission beam for PUCCH resources after receiving a physical downlink control channel (PDCCH), using power control parameters and spatial relation information to recover the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reference signal is provided for each PUCCH resource to provide spatial relation information, then the transmission beam can be determined, but when beam failure occurs, there is no reference signal available and thus no mechanism to recover the transmission beam
Solution Approach 1:
The patent applies preliminary action by pre-configuring default spatial relation information and default downlink reference signals for PUCCH resources before beam failure occurs. When beam failure is detected, the UE can immediately use these pre-configured defaults without requiring complex real-time reference signal configurations, enabling rapid beam recovery while maintaining system reliability.
2Reliability
If contention-based RACH is initiated upon detecting beam failure, then beam recovery can be achieved, but the process requires coordination of multiple signaling messages and procedures
Solution Approach 1:
The patent applies preliminary action by pre-configuring default spatial relation information and default downlink reference signals for PUCCH resources before beam failure occurs. When beam failure is detected, the UE can immediately use these pre-configured defaults without requiring complex real-time reference signal configurations, enabling rapid beam recovery while maintaining system reliability.
Solution Approach 2:
The patent implements feedback mechanisms where the network monitors RACH messages from the UE during beam failure recovery. The network provides feedback through RACH response messages and subsequent PDCCH transmissions, allowing the UE to adjust its beam selection and confirm successful recovery, thereby reducing unnecessary retransmissions and optimizing recovery time.
Data Source
AI summary
Methods and systems for starting a contention-based random-access channel (RACH) upon detecting beam failure of a serving cell. The method includes transmitting a medium access control (MAC) control element (CE), signaling the beam failure of the serving cell in a message of the contention-based RACH. The method further includes determining completion of the contention-based RACH based on receipt of a physical downlink control channel (PDCCH); and after receiving one or more of the last symbols of the PDCCH, determining a default transmission (Tx) beam for each resource of a physical uplink control channel (PUCCH) that includes a PUCCH spatial relation information parameter.