Beam Failure Recovery Scheduling Request Retransmission
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Solution Overview
Problem
Wireless communication systems face challenges in efficiently recovering from beam failures in secondary cells, particularly when beam failure recovery requests are not acknowledged by the base station or when the necessary control elements to recover from the failure are not transmitted, leading to disruptions in communication.
Innovation Solution
A method where user equipment (UE) transmits a beam failure recovery scheduling request (BFR-SR) to a primary or primary secondary cell base station, starts a timer, and retransmits the BFR-SR if no response is received or if the UE has not transmitted the required medium access control (MAC) control element to recover from the beam failure before the timer expires, ensuring persistent attempts within a configured threshold to initiate recovery procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE transmits BFR-SR to initiate beam failure recovery, then the beam failure recovery process is started, but the recovery may not be completed if the base station does not acknowledge or if MAC-CE is not transmitted promptly
Solution Approach 1:
The UE performs preliminary actions by transmitting the BFR-SR and starting a timer before the actual recovery is confirmed. This preliminary initiation ensures that the recovery process is triggered as early as possible, and the timer mechanism is pre-configured to automatically handle retransmission if needed, reducing overall recovery time while maintaining reliability.
Solution Approach 2:
The timer mechanism provides feedback control for the BFR-SR transmission. When the timer expires without receiving acknowledgment or MAC-CE transmission confirmation, the UE automatically retransmits the BFR-SR. This feedback loop ensures reliable recovery initiation while managing the timing aspects of the recovery process.
2Reliability
If the UE retransmits BFR-SR upon timer expiration, then the probability of successful recovery initiation increases, but network loading increases
Solution Approach 1:
The UE performs partial retransmission actions only when necessary - specifically when the timer expires without confirmation of successful recovery initiation. This partial action approach (retransmitting only when needed rather than continuously) increases the probability of successful recovery while avoiding excessive network loading from unnecessary retransmissions.
Solution Approach 2:
The timer parameter controls the retransmission behavior. By adjusting the timer duration, the system balances between reliability (longer timer allows more time for single transmission to succeed) and network loading (shorter timer triggers earlier retransmission if needed). This parameter-based control allows optimization of the trade-off between recovery success rate and network resource consumption.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a beam failure recovery scheduling request (BFR-SR) to a primary cell or a primary secondary cell base station based at least in part on detecting a beam failure associated with a secondary cell (SCell) link between the UE and an SCell base station. The UE may start a timer based at least in part on transmitting the BFR-SR. The UE may retransmit the BFR-SR based at least in part on the timer expiring prior to the UE receiving a response to acknowledge the BFR-SR and schedule transmission of a medium access control (MAC) control element (MAC-CE) including information to recover from the beam failure and/or the timer expiring prior to the UE transmitting the MAC-CE. Numerous other aspects are provided.