RACH-less Handover Timing Advance Determination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional handover procedures in wireless communications require unnecessary time for Timing Advance (TA) determination after the handover has been initiated, which increases the overall handover time due to the Random-Access Channel (RACH) procedure.
Innovation Solution
Implementing RACH-less handovers by having the source base station inform and configure the UE device with a radio transmission configuration before handover, allowing the target base station to calculate and signal the TA before the handover procedure, thereby skipping the RACH transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the conventional handover procedure is used with RACH for TA determination, then the TA can be accurately determined after handover, but the handover time is increased due to the additional RACH procedure time
Solution Approach 1:
The source base station performs preliminary actions by determining the TA value before the handover is executed. The source eNB calculates the TA based on uplink signals received from the UE device while still connected to the source base station, and then signals this pre-determined TA to the target base station, which includes it in the handover command. This preliminary determination eliminates the need for post-handover RACH procedures for TA measurement, thereby reducing handover time while maintaining accuracy.
2Reliability
If the RACH procedure is performed after handover for TA calculation, then the TA can be determined based on actual uplink signals to the target base station, but the handover completion is delayed
Solution Approach 1:
The source base station acts as an intermediary to transfer the TA value to the target base station. Instead of the target base station directly measuring TA from uplink signals after handover (which would require RACH procedure), the source base station measures the uplink signals, calculates TA, and signals this information to the target base station. This intermediary approach allows the target base station to obtain accurate TA information without performing the time-consuming RACH procedure, thus reducing handover delay while maintaining reliability.
Data Source
AI summary
RACH-less handovers can be used to reduce the additional time required to complete the RACH procedure when the Timing Advance (TA) must be determined as part of the handover procedure. In order to facilitate a RACH-less handover, the source base station informs the target base station of a radio transmission configuration that will be used by the UE device to transmit uplink signals to the source base station, and the source base station configures the UE device in accordance with the radio transmission configuration. The UE device transmits uplink signals to the source base station using the specified radio transmission configuration, and the target base station receives the uplink signals. The UE device transmits these uplink signals to the source base station before the handover procedure is initiated. The target base station calculates the TA, based on the uplink signals, which can be signaled to the UE device in a handover command.