Pre-synchronization for Wireless Handover Interruption
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Solution Overview
Problem
In asynchronous wireless cellular networks, handover interruptions are significant due to the latency involved in uplink synchronization during the process of transitioning from one base station to another, particularly in LTE networks where initial RACH access is required for timing advance computation.
Innovation Solution
A pre-synchronization method where the source base station chooses a signature for the user equipment to use in the target base station and instructs it to perform RACH access in parallel with the context transfer process, reducing handover interruption time by executing the uplink synchronization process concurrently with the context transfer among base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If initial RACH access is required for timing advance computation during handover, then uplink synchronization can be achieved, but handover interruption time increases
Solution Approach 1:
The source base station performs timing advance computation and provides timing advance information to the user equipment before the handover command is executed. The user equipment applies this timing advance information during the handover to the target base station, eliminating the need for initial RACH access and timing advance computation after handover, thus reducing handover interruption time while maintaining reliable uplink synchronization
2Loss of time
If parallel execution of synchronization and context transfer is implemented, then handover interruption time is reduced, but process complexity increases
Solution Approach 1:
The source base station computes timing advance information in advance during the handover preparation phase and includes it in the handover command. This preliminary action allows the user equipment to perform uplink synchronization immediately upon receiving the handover command, enabling parallel execution of synchronization and context transfer without requiring complex coordination mechanisms during the handover execution phase
Solution Approach 2:
The source base station acts as an intermediary by computing the timing advance information that would normally be computed by the target base station after handover. By providing this timing advance information through the handover command, the source base station enables the user equipment to synchronize with the target base station without requiring initial RACH access, thus reducing handover interruption time while managing process complexity
Data Source
AI summary
A pre-synchronization method in which the source cell chooses a signature for the user equipment (mobile) to use in the target cell for RACH access, and instructs the user equipment to perform RACH access and return to the current cell before a handover command (break command) is issued. This causes parallel execution of the UL synchronization process with the context transfer process among the two base stations.