F1 Message Transfer for Uplink Synchronization in Inter-DU Mobility
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Solution Overview
Problem
In existing communication systems, when a user equipment moves between cells with different gNB-DUs, the source cell cannot acquire the necessary random access configuration or timing advance (TA) of the candidate cell, leading to delays and interruptions during L1/L2-based inter-cell mobility.
Innovation Solution
A mechanism is introduced where a network device CU transmits a first F1 message to a candidate cell's DU, providing information for uplink synchronization, including random access configuration and TA, enabling the source cell to trigger PDCCH ordered RA on the candidate cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the source cell performs L1/L2-based inter-cell mobility to a candidate cell with different gNB-DU, then mobility speed is improved, but the source cell cannot acquire random access configuration or TA of the candidate cell, causing delays and interruptions
Solution Approach 1:
The network device CU performs preliminary action by transmitting the first F1 message to the candidate cell's gNB-DU before the actual mobility event, so that the random access configuration and TA information are prepared and transmitted in advance. This allows the source cell to acquire the necessary synchronization information before the mobility execution, reducing interruption time during the actual cell switching process.
Solution Approach 2:
The network device CU acts as an intermediary between the source cell and the candidate cell's gNB-DU. It receives the first F1 message from the candidate cell's gNB-DU containing random access configuration and TA information, then facilitates the transmission of this information to the source cell. This intermediary mechanism enables information exchange between cells with different gNB-DUs that would otherwise be unable to communicate directly.
2Reliability
If the source cell triggers PDCCH ordered RA on the candidate cell, then uplink synchronization is achieved, but the complexity of information transmission between cells increases
Solution Approach 1:
The invention extracts the essential information needed for uplink synchronization (random access configuration and TA) from the complex F1 message and transmits only these critical parameters from the network device CU to the source cell. This extraction approach maintains the reliability of uplink synchronization while reducing the complexity of information transmission by filtering out unnecessary data.
Solution Approach 2:
The invention changes the parameter format of the F1 message by defining a specific structure that includes the random access configuration and TA information in a standardized manner. This parameter change enables efficient information transmission and processing, reducing complexity while ensuring reliable uplink synchronization through structured data exchange.
Data Source
AI summary
An information transfer apparatus includes: processor circuitry; and a first transmitter configured to transmit, by the processor circuitry, a first F1 message comprising information for obtaining uplink synchronization on a candidate cell to a first network device DU (distributed unit) by a network device CU (central unit).