L1/L2 Mobility Latency Reduction via Scheduling Gap Uplink Sync
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Solution Overview
Problem
Current telecommunications systems face latency issues during L1/L2 triggered inter-cell changes in disaggregated architectures, particularly due to delays in the random access channel (RACH) procedure during handovers, which can exceed 10-20 ms, and lack efficient methods for beam-based inter-cell mobility.
Innovation Solution
The system indicates a scheduling gap duration to user equipment (UE) to perform uplink sync and preamble transmission with the target cell during this gap, allowing for timing advance acquisition without explicit RACH, and enables UE to determine preferable beams for neighboring cells, thereby reducing latency and facilitating beam-based inter-cell mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the random access channel (RACH) procedure is performed during handover, then uplink synchronization can be achieved, but latency increases by 10-20 ms
Solution Approach 1:
The network performs uplink timing advance adjustment and synchronization in advance during the scheduling gap, before the actual handover execution. The UE sends a preamble to the target cell and receives timing advance information during the scheduling gap, so that when handover occurs, synchronization is already established, eliminating the need for post-handover RACH procedures.
2Ease of operation
If explicit RACH procedure is used for handover, then random access can be performed, but latency is increased
Solution Approach 1:
The patent extracts and removes the explicit RACH procedure from the handover process by performing the necessary random access function (preamble transmission and timing advance acquisition) during the scheduling gap before handover execution. This separation allows handover to proceed without the full RACH latency overhead.
3Speed
If L1/L2 triggered mobility is implemented without scheduling gap, then handover speed increases, but uplink sync and timing advance acquisition cannot be performed
Solution Approach 1:
The patent segments the handover process into distinct phases: a scheduling gap phase for uplink synchronization and timing advance acquisition, and an execution phase for actual handover. This segmentation allows both synchronization requirements and fast handover speed to be achieved by separating the preparatory synchronization actions from the critical handover transition.
Data Source
AI summary
Provided are method, system, and device for configuring inter-cell changes. The method may be implemented by receiving, by a user equipment (UE), a downlink signal, wherein the downlink signal originates from a serving distributed unit (DU), and wherein the downlink signal comprises at least one of a scheduling gap duration value, a start time value, and a target cell index; performing, by the UE during the scheduling gap duration, an uplink sync with a target cell, based on the downlink signal; and wherein the uplink sync includes sending, by the UE, a preamble transmission to a target cell to acquire a timing advance of the target cell, based on the downlink signal, wherein the target DU is one of a plurality of neighboring cells to the serving DU.