SCell Beam Failure Recovery via Pre-configured Candidate Beams
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in efficiently handling beam failure events, especially in Frequency Range 2 (FR2) due to millimeter wave propagation characteristics, which lead to frequent beam blockages, necessitating an improved mechanism for User Equipment (UE) to recover from beam failures in Secondary Cells (SCells).
Innovation Solution
A method for beam failure recovery (BFR) procedure performed by User Equipment (UE) involves detecting beam failures, identifying new candidate beams, transmitting a beam failure recovery request, and receiving network responses to establish a new beam pair link, utilizing explicit or implicit configurations of reference signals and quasi-co-location references to restore connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beam failure recovery procedure is implemented in SCell for FR2, then connectivity reliability is improved, but device complexity increases
Solution Approach 1:
The network configures the UE with candidate beam reference signals and recovery request resources in advance before beam failure occurs. This preliminary configuration enables the UE to quickly execute recovery procedures without complex real-time decision-making, thus improving reliability while managing device complexity
Solution Approach 2:
The UE autonomously detects beam failure conditions, selects candidate beams from pre-configured options, and transmits recovery requests without continuous network intervention. This self-service approach improves connectivity reliability through rapid autonomous recovery while avoiding the complexity of continuous network-UE coordination
2Speed
If beam failure recovery procedure is implemented in SCell for FR2, then beam blockage recovery speed is improved, but loss of time in recovery process increases
Solution Approach 1:
Candidate beams and recovery resources are pre-configured before beam failure occurs. When failure is detected, the UE can immediately transmit recovery requests using pre-allocated resources without waiting for network allocation, thus improving recovery speed while minimizing additional time loss
Solution Approach 2:
The UE skips traditional random access procedures by directly transmitting beam failure recovery requests on pre-configured uplink resources. This bypasses unnecessary steps in the recovery process, improving speed while keeping the overall time loss acceptable
Data Source
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AI summary
A method for SCell BFR performed by a UE is provided. The method includes: transmitting, to a base station, a BFR MAC CE that includes a cell index of an SCell in which beam failure occurs and a new candidate beam index for the SCell, the transmission of the BFR MAC CE associated with a HARQ process having a HARQ process ID; and receiving, from the base station, a first DCI format that schedules a first PUSCH transmission with the HARQ process ID, the first DCI format indicating a toggled NDI value.