Default Uplink Beam Determination After RRC Reestablishment
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Solution Overview
Problem
In mmWave wireless communication networks, there is a challenge in determining the appropriate uplink transmission beam after radio resource control (RRC) connection reestablishment, as the user equipment (UE) lacks information on which transmission beam to use for physical uplink control channel (PUCCH) transmission before receiving a dedicated PUCCH configuration.
Innovation Solution
A method is proposed where the UE determines a default uplink beam for PUCCH transmission based on the beam used during the RRC connection reestablishment procedure, specifically the beam used for the MSG3 transmission in the four-step random-access channel (RACH) procedure, allowing PUCCH transmission to proceed before a dedicated PUCCH configuration is received.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the UE uses the beam from RRC connection reestablishment procedure for PUCCH transmission, then uplink control information can be transmitted during transition phase, but the beam may not be optimal for dedicated PUCCH resources
Solution Approach 1:
The patent applies preliminary action by having the UE determine and use a default spatial filter for PUCCH transmission during the transition phase before dedicated PUCCH configuration is received. This default spatial filter is determined based on the RACH procedure that already occurred, allowing the UE to proactively prepare and transmit uplink control information without waiting for network configuration, thus maintaining transmission continuity while avoiding service interruption
Solution Approach 2:
The patent uses the RACH procedure as an intermediary to establish a default spatial filter that serves as a temporary solution. The beam information obtained during RACH acts as a mediator between the connection reestablishment event and the receipt of dedicated PUCCH configuration, enabling the UE to perform PUCCH transmission in the interim period with acceptable beam quality
2Reliability
If the UE waits for dedicated PUCCH configuration before transmitting PUCCH, then optimal beam can be used, but communication interruption occurs during transition phase
Solution Approach 1:
The UE performs preliminary determination of the default spatial filter based on the RACH procedure before the dedicated PUCCH configuration is received from the network. This allows the UE to immediately transmit PUCCH upon connection reestablishment without waiting for network configuration, eliminating communication interruption and ensuring continuous uplink control information delivery
Solution Approach 2:
The UE autonomously determines its own default spatial filter for PUCCH transmission by utilizing information from the RACH procedure it already performed. This self-service approach eliminates the need to wait for network-provided beam configuration, reducing latency and maintaining communication continuity during the transition phase
Data Source
AI summary
A method of default uplink beam determination after radio resource control (RRC) connection reestablishment in a beamforming system is proposed. For uplink (UL) transmission, the BS provides dedicated physical uplink control channel (PUCCH) resource configuration to UE. The configuration includes spatial relation information that indicates the spatial domain transmission filter to be used by UE for the corresponding PUCCH transmission. After RRC connection re-establishment and before a dedicated PUCCH configuration is received, a default UE TX beam can be determined based on the UE TX beam used during the RRC connection re-establishment procedure, e.g., the UE TX beam used to transmit MSG3 in a four-step random-access channel (RACH) procedure triggered by the RRC connection re-establishment procedure.