5G DU-CU Synchronization for Faster Lower-Layer Cell Switching
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Solution Overview
Problem
Current 3GPP 5G technologies lack detailed discussions on uplink (UL) synchronization and downlink (DL) synchronization in lower layer-based mobility scenarios, particularly during cell switching.
Innovation Solution
The proposed solution involves a candidate distributed unit (DU) and centralized unit (CU) of a base station that exchange messages via the F1 interface to provide RRC configuration, RACH configuration, and indications for early TA acquisition and DL synchronization operations before cell switching, using indications and information elements (IEs) to manage UE mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If early TA acquisition and DL synchronization operations are performed before cell switching, then UL and DL synchronization is enhanced, but processing delays and signaling overhead increase
Solution Approach 1:
The patent performs TA acquisition and DL synchronization operations in advance before cell switching is actually needed. The CU receives RACH configuration information from the candidate DU and stores it for later use, allowing the UE to quickly switch cells without performing these time-consuming operations after switching is initiated.
Solution Approach 2:
The patent extracts and separates the TA acquisition and DL synchronization operations from the cell switching procedure itself. These operations are performed independently in advance, and their results are stored and reused during cell switching, reducing the overall processing time of the switching procedure.
2Measurement precision
If detailed RRC configuration information and RACH configuration information are exchanged between CU and candidate DU, then synchronization accuracy is improved, but signaling overhead increases
Solution Approach 1:
The CU receives and stores RACH configuration information from the candidate DU in advance, before it is actually needed for cell switching. This preliminary exchange allows the configuration to be reused multiple times without repeated signaling, reducing overall overhead while maintaining accuracy.
Solution Approach 2:
The patent merges the RACH configuration information exchange into the existing F1 interface signaling between CU and DU. By integrating this configuration exchange into existing message structures rather than creating separate dedicated signaling, the overhead is minimized while still transmitting all necessary configuration details.
Data Source
AI summary
Embodiments of the present application relate to methods and apparatuses for uplink (UL) synchronization and downlink (DL) synchronization in a lower layer-based mobility case under a 3rd Generation Partnership Project (3GPP) 5G system or the like. According to an embodiment of the present application, a candidate distributed unit (DU) of a base station (BS) includes a transceiver 2024/082427 and a processor coupled to the transceiver, and the processor is configured to cause the candidate DU to: receive a request from a centralized unit (CU) of the BS, wherein the request includes identifier (ID) information of one or more candidate cells; and transmit, based on the request, a response message to the CU, wherein the response message is associated with a cell switching procedure.