Neighbor-Cell Random Access Feedback for Faster Handover
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Solution Overview
Problem
During cell handover, terminal devices experience service interruptions due to the inability to receive data from the serving cell while initiating random access to a candidate cell, and there is a need to determine the success of the random access without prolonging the interruption time.
Innovation Solution
The terminal device determines the success of random access by receiving feedback from the serving network device instead of waiting for a response from the candidate cell, allowing it to retransmit the access request if necessary, and obtaining necessary parameters like TA, identifier, and uplink resources in advance to minimize service interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal device waits to receive the response message from the candidate cell for the preamble, then the terminal device can determine whether random access succeeds, but the service interruption time of the terminal device in the serving cell increases
Solution Approach 1:
The serving network device acts as an intermediary that receives the random access response from the candidate cell and forwards it to the terminal device. This allows the terminal device to determine random access success without directly waiting for the candidate cell's response, thereby reducing service interruption time while maintaining accurate access determination.
Solution Approach 2:
The random access procedure is segmented into independent stages: the terminal device sends the preamble to the candidate cell independently, while simultaneously maintaining communication with the serving cell. The serving network device separately receives and forwards the response, allowing parallel processing and reduced waiting time.
2Loss of time
If the terminal device does not wait to receive the response message from the candidate cell for the preamble, then the service interruption time is reduced, but the terminal device cannot determine whether random access succeeds
Solution Approach 1:
The serving network device serves as a mediator that bridges the terminal device and the candidate cell. It receives the random access response containing success/failure information and relays it to the terminal device, enabling the terminal to determine access status without directly waiting for the candidate cell.
Solution Approach 2:
A feedback mechanism is established where the serving network device provides the terminal device with the outcome of the random access procedure. This feedback loop allows the terminal device to accurately determine whether random access succeeded without prolonging the interruption time.
3Adaptability or versatility
If the terminal device initiates random access to the candidate cell, then the terminal device can hand over to the target cell, but the terminal device cannot receive data from the serving cell during the random access process
Solution Approach 1:
The handover process is segmented such that the random access procedure to the target cell is separated from the data reception process with the serving cell. The terminal device can maintain or quickly resume data reception with the serving cell while independently completing the random access to the target cell through the intermediary mechanism.
Solution Approach 2:
The terminal device performs preliminary actions by sending the random access preamble to the candidate cell before fully disconnecting from the serving cell. The serving network device is already positioned to receive and forward the response, preparing the path for seamless handover with minimal interruption.
Data Source
AI summary
A communication method and a related apparatus. A terminal device sends a random access request to a neighboring-cell network device, where the random access request is usable to initiate random access to a target neighboring cell, where the target neighboring cell is a neighboring cell of a serving cell of the terminal device. The terminal device retransmits the random access request to the neighboring-cell network device in response to the terminal device receiving a first scheduling signaling from the serving network device, where the first scheduling signaling is usable to schedule the terminal device to retransmit the random access request.