SUL Failure Handling via Uplink Carrier Switching
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Solution Overview
Problem
The detection and reporting of radio link failures (RLFs) in scenarios involving supplementary uplink (SUL) carriers pose challenges, leading to undesirable service interruptions and increased signaling overhead, particularly in EN-DC environments where UE is configured with two UL carriers and one DL carrier, and existing methods are not suitable for handling SUL failures effectively.
Innovation Solution
The techniques involve the UE performing a UL switch to the ordinary UL carrier upon detecting an RLF on the SUL carrier, without initiating RRC re-establishment, and sending a report to the network, allowing the network to configure a new SUL carrier or continue using the unaffected UL carrier, thereby minimizing service interruptions and signaling overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE initiates RRC re-establishment upon detecting RLF on SUL carrier, then the radio link failure is handled according to existing procedures, but service interruption time increases and signaling overhead increases
Solution Approach 1:
The patent segments the failure handling procedure by distinguishing between SUL carrier failures and ordinary UL carrier failures. When RLF is detected on the SUL carrier, the UE switches to the ordinary UL carrier for reporting instead of initiating full RRC re-establishment, thereby separating the reporting path from the failure recovery path and reducing service interruption time.
Solution Approach 2:
The ordinary UL carrier acts as an intermediary resource that the UE can use to report SUL carrier failures. This intermediary channel allows the UE to communicate failure information without needing to re-establish the entire RRC connection, thus reducing signaling overhead and service interruption while maintaining reliability.
2Reliability
If the UE initiates RRC re-establishment upon detecting RLF on SUL carrier, then the radio link failure is handled according to existing procedures, but signaling overhead increases
Solution Approach 1:
The patent segments the signaling paths by allowing different reporting mechanisms for different carrier types. SUL carrier failures are reported through the ordinary UL carrier using existing uplink resources, while ordinary UL carrier failures trigger full RRC re-establishment. This segmentation reduces unnecessary signaling overhead for SUL failures while maintaining adequate handling for critical failures.
Solution Approach 2:
The ordinary UL carrier serves as an intermediary communication channel that reduces signaling overhead. By using this existing carrier to report SUL failures, the system avoids the extensive signaling exchange required for full RRC re-establishment, thereby reducing information loss in terms of signaling efficiency.
3Reliability
If the UE uses only one UL carrier at a time in SUL configuration, then the uplink coverage is improved through carrier selection, but the complexity of carrier management increases
Solution Approach 1:
The patent implements self-service by enabling the UE to autonomously switch to the ordinary UL carrier when SUL carrier failure is detected, without requiring complex network coordination or additional configuration management. The UE independently manages the carrier switch and uses existing resources for failure reporting, thereby reducing overall system complexity while maintaining uplink coverage reliability.
Data Source
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AI summary
A UE (50) is configured to receive data from a serving node via a downlink carrier and to transmit data to the serving node (30) via selective use of a first uplink carrier and an associated supplementary uplink, SUL, carrier, such that only one of the carriers is used by the UE (50) at any given time. The UE (50) detects (502) a radio link problem for a currently used one of the first uplink carrier and the associated SUL carrier. Responsive to said detecting, the UE(50) transmits (504) a random access preamble to the serving node (30) on the first uplink carrier or the associated SUL carrier. The serving node (30) receives (302) an uplink failure report from the UE (50) and may then release (304) the first uplink carrier or the associated SUL carrier, with respect to the UE (50), in response.