Uplink Timing Synchronization Omission in LTE Handover
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Solution Overview
Problem
In mobile communication systems, particularly in 3GPP LTE, the uplink timing synchronization procedure during handover to a target cell causes unnecessary delays and signaling overhead, as existing methods require synchronization even when the uplink timings of the source and target cells are identical or nearly identical.
Innovation Solution
A method and apparatus that determine, based on a handover command message, whether an uplink timing synchronization procedure is needed with the target cell, allowing for the omission of this procedure if the uplink timings are identical, thereby reducing unnecessary delays and overhead by maintaining the source cell's uplink timing in the target cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uplink timing synchronization procedure is performed during handover to target cell, then uplink timing alignment is ensured, but service delay and signaling overhead increase unnecessarily when source and target cell timings are identical
Solution Approach 1:
The patent applies partial action by performing timing synchronization only when necessary. The UE determines whether synchronization is needed by comparing uplink timing values from source and target cells, and only executes the synchronization procedure when the timing difference exceeds a threshold, avoiding unnecessary full synchronization procedures
Solution Approach 2:
The patent changes the parameter of timing synchronization execution from a fixed mandatory action to a conditional action based on timing parameter comparison. The UE evaluates the uplink timing parameter (N_TA) from handover commands and decides whether to perform synchronization based on whether the parameter indicates a significant timing difference
2Reliability
If uplink timing synchronization procedure is performed during handover, then timing alignment is maintained, but signaling overhead increases due to unnecessary synchronization messages
Solution Approach 1:
The patent reduces signaling overhead by performing partial synchronization actions only when needed. The UE skips unnecessary synchronization message exchanges (such as random access preamble transmission and timing adjustment messages) when the timing comparison indicates the source and target cells have identical or nearly identical uplink timings
3Productivity
If uplink timing synchronization procedure is omitted during handover, then service delay and signaling overhead are reduced, but uplink timing alignment may be compromised
Solution Approach 1:
The patent uses parameter-based decision making where the UE evaluates the uplink timing parameter (N_TA) provided in the handover command. When this parameter indicates that the timing difference is within an acceptable range, the UE changes its behavior to omit synchronization, thereby improving handover speed while maintaining sufficient timing alignment through the parameter guidance
Data Source
AI summary
An efficient uplink timing synchronization procedure performed with a target cell upon handover of a User Equipment (UE) in active mode in a mobile communication system is provided, in which a cell transmitter signals to the UE that the uplink timing synchronization procedure is not required in the target cell, and the UE carries out uplink transmission to the target cell at an uplink timing used in a source cell without the uplink timing synchronization procedure.