Timing Advance Handover Using SRS Instead of Random Access
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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 a timing advance (TA) in a new cell, leading to synchronization issues.
Innovation Solution
A method for a terminal device to adjust timing advance without random access by sending a sounding reference signal (SRS) to a new cell based on a pre-determined TA, using a first TA calculated from the existing TA and the time difference of arrival between reference signals of the current and target cells, and adjusting based on a received command from the new cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If random access is performed to obtain TA in the new cell during handover, then TA can be accurately acquired, but uplink signal transmission interruption time increases
Solution Approach 1:
The terminal device performs TA calculation in advance based on downlink reference signal time difference (RSTD) measurement before handover occurs. The calculated TA value is prepared and ready to be applied immediately upon receiving the handover command, eliminating the need for random access procedures in the target cell. This preliminary action resolves the contradiction by achieving both accurate TA acquisition and minimal transmission interruption.
2Reliability
If random access procedure is executed for TA acquisition in target cell, then synchronization can be established, but handover process complexity increases
Solution Approach 1:
The patent extracts the TA acquisition function from the random access procedure by implementing independent TA calculation based on RSTD measurement. The terminal device calculates TA using the formula TA = T0 + ΔTA, where T0 is the uplink transmission timing in the source cell and ΔTA is the timing adjustment based on downlink reference signal time difference. This extraction eliminates the need for random access while maintaining synchronization reliability and reducing handover complexity.
3Speed
If TA is calculated based on RSTD measurement, then TA acquisition speed improves, but measurement precision requirements increase
Solution Approach 1:
The patent implements a feedback mechanism where the calculated TA value is applied and its effectiveness is monitored through uplink signal reception at the network side. The network device can provide feedback on whether the uplink timing is appropriate, allowing the terminal to refine its RSTD measurements and TA calculations. This feedback loop ensures that even with varying measurement conditions, the system achieves both fast TA acquisition and adequate precision through iterative optimization.
Data Source
AI summary
This disclosure relates to the field of communication technologies, and discloses a timing advance adjustment method and an apparatus. 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 (SRS) to the second cell based on a first 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.