L1/L2 Inter-Cell Mobility Using CSI-RS for Fast Handover
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Solution Overview
Problem
Existing 5G/NR mobile communication systems face challenges with high latency and signaling overhead in network-controlled mobility due to layer 3-based handover procedures, particularly in scenarios involving frequent handovers and high-speed vehicular environments.
Innovation Solution
Implementing an L1/L2-based inter-cell mobility mechanism that triggers handover through layer 1/layer 2 signaling, utilizing channel status information-reference signals (CSI-RS) for measurements and beam switching decisions, allowing for reduced latency and signaling overhead by enabling beam switching without a random access procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If network-controlled mobility with higher layer signaling is used for handover, then handover control and reliability are improved, but signaling overhead and latency increase
Solution Approach 1:
The patent segments the handover control function into two parts: L1/L2 measurements and reporting are performed by the UE autonomously, while the final handover decision and execution are controlled by the network through simplified signaling. This segmentation allows faster measurement processing at UE side while maintaining network control, reducing overall handover latency without sacrificing reliability
Solution Approach 2:
The patent implements preliminary measurement and reporting actions at L1/L2 layer before the actual handover decision is made by the network. The UE continuously performs measurements and prepares reports in advance, so when handover is needed, the network already has up-to-date measurement data, enabling faster decision-making and reducing handover latency
2Reliability
If network-controlled mobility with higher layer signaling is used for handover, then handover control is maintained, but signaling overhead increases
Solution Approach 1:
The patent extracts the measurement and reporting functions from the higher layer (L3) signaling process and places them at the L1/L2 layer. This extraction eliminates the need for extensive L3 measurement reports and handover request signaling, significantly reducing signaling overhead while the network retains control through essential L1/L2 feedback mechanisms
Solution Approach 2:
The patent enables the UE to autonomously perform measurements and generate reports at L1/L2 layer without requiring network-initiated measurement configurations and report requests. This self-service approach at the physical and MAC layers reduces the back-and-forth signaling between network and UE, minimizing signaling overhead while maintaining accurate measurement data for network-controlled handover decisions
3Adaptability or versatility
If frequent handovers occur in high-speed vehicular scenarios, then mobility coverage is maintained, but connection interruption and latency accumulate
Solution Approach 1:
The patent ensures continuous measurement and reporting actions at L1/L2 layer during high-speed movement, allowing the network to maintain uninterrupted knowledge of UE location and channel conditions. This continuity enables seamless handover execution without connection interruption, as the network can proactively prepare target cell resources based on ongoing L1/L2 feedback even during frequent handovers in vehicular scenarios
Data Source
AI summary
Methods and apparatuses for L1/L2 mobility control in a wireless communication system. A method of a UE comprises receiving, from a BS, a message including L1/L2 mobility configuration information. The method includes measuring, based on a CSI-RS received from at least one candidate cell of candidate BS, L1-reference signal received power (L1-RSRP), L1-reference signal received quality (L1-RSRQ), and L1-signal to interference and noise ratio (L1-SINR) of the at least one candidate cell. The method includes reporting the L1-RSRP, the L1-RSRQ, and the L1-SINR of the at least one candidate cell. The method further includes receiving an L1/L2 signal to trigger a handover (HO) operation to the target cell, wherein the L1/L2 signal includes a transmission configuration indicator (TCI) state switch to the target cell.