L1/L2 Handover Failure Reporting for Wireless UE
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Solution Overview
Problem
Conventional wireless communication systems lack effective mechanisms for a user equipment (UE) to report handover failures to the source base station, leading to potential data loss and inefficient handover processes in layer one or layer two based cell handover procedures.
Innovation Solution
The implementation of a method where the UE initiates a timer at the physical layer to monitor for control signals from the target base station during a handover, and if unsuccessful, transmits a failure report to the source base station, allowing for re-establishment of connections and identification of new target base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional handover techniques are used without failure reporting mechanisms, then the handover procedure can be completed, but handover failures cannot be detected and reported, leading to data loss and inefficient handover processes
Solution Approach 1:
The patent implements a feedback mechanism where the UE monitors for control signals (RACH signals, resource release commands) from the target base station during handover. If these signals are not received within an expected timeframe, the UE generates a handover failure report containing information about the failed handover and sends it back to the source base station. This feedback loop enables the network to detect and respond to handover failures, preventing data loss and improving reliability.
2Reliability
If the UE monitors for control signals during handover, then handover failures can be detected, but the monitoring process adds complexity to the handover procedure
Solution Approach 1:
The patent applies preliminary action by having the UE initiate a timer at the physical layer (L1) before actually monitoring for control signals during handover. This timer is started in advance based on expected handover timing, allowing the UE to be ready to detect failures without complex real-time decision-making. The timer-based approach simplifies the monitoring logic while maintaining reliable failure detection.
3Loss of time
If the UE transmits a failure report to the source base station, then handover failures can be reported timely, but additional signaling overhead is introduced
Solution Approach 1:
The patent changes the parameter of failure reporting by transmitting the handover failure report at the physical layer (L1) or medium access control layer (L2) rather than requiring higher-layer signaling. This parameter change in the reporting layer enables timely failure notification with reduced signaling overhead, as L1/L2 signaling is more efficient and faster than traditional RRC signaling for urgent notifications.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may establish a first connection with a source base station. The UE may determine that a handover procedure is being performed for establishing a second connection with a target base station. The UE may monitor, during a monitoring period instantiated at a physical layer of a protocol stack of the UE, for a control signal acknowledging success of the handover procedure from a target base station. The UE may transmit, based at least in part on a result of the monitoring during the monitoring period, a physical layer signal or a medium access control layer signal to the source base station indicating that the handover procedure was unsuccessful based at least in part on a failure to successfully receive and decode the control signal.