Timing Advance Adjustment for Random-Access-Free Cell Handover
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Solution Overview
Problem
During cell handover, terminal devices experience long interruptions in uplink signal transmission due to the need for random access to obtain timing advance (TA) in new cells, leading to synchronization issues.
Innovation Solution
A method for terminal devices to adjust timing advance without random access by sending a sounding reference signal (SRS) based on a pre-determined TA, using a TA adjustment command from the new cell, and synchronizing uplink signals with the new cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If random access is used to obtain TA in new cell during handover, then TA can be obtained, but uplink signal transmission interruption time increases
Solution Approach 1:
The terminal device sends SRS to the new cell before handover completion using the current TA value, allowing the new cell to calculate and provide TA adjustment command in advance, thus avoiding the need for random access after handover and reducing uplink transmission interruption time
Solution Approach 2:
SRS is used as an intermediary signal to carry uplink transmission from the terminal device to the new cell during handover, enabling the new cell to measure the uplink timing and provide TA adjustment command without requiring random access procedure
2Reliability
If random access is performed during cell handover, then TA can be obtained, but handover complexity increases
Solution Approach 1:
The TA measurement and calculation function is extracted from the random access procedure and performed separately through SRS transmission, allowing TA to be obtained without executing the complete random access protocol and thus reducing handover complexity
Solution Approach 2:
The terminal device autonomously sends SRS to the new cell using existing TA information, and the new cell autonomously calculates and returns the TA adjustment command, eliminating the need for multi-step random access interaction and simplifying the handover procedure
Data Source
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AI summary
This application relates to the field of communication technologies, and discloses a timing advance adjustment method and an apparatus, to support cell handover of a terminal device without random access, and reduce interruption time of uplink signal transmission of the terminal device during cell handover. The method includes: A terminal device receives a handover command from a first cell, where the handover command instructs to perform handover to a second cell, sends a sounding reference signal (sounding reference signal, SRS) to the second cell based on a first timing advance (timing advance, TA), receives a TA adjustment command from the second cell, where the TA adjustment command includes an adjustment amount for the first TA, and the adjustment amount is determined by the second cell based on the received SRS, and sends an uplink signal to the second cell based on a second TA, where the second TA is determined based on the first TA and the adjustment amount.