Timing Advance Transfer for Low-Interruption Inter-Cell Mobility
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Solution Overview
Problem
Current 5G NR wireless networks face challenges in maintaining uplink synchronization during inter-cell mobility, leading to increased latency and interruption times due to the need for random access procedures with target cells, which can cause interference and reduce data rates.
Innovation Solution
A method for establishing timing advance (TA) management between user equipment (UE) and target candidate cells using uplink configurations and TA values received from the serving cell, allowing L1/L2 inter-cell mobility without performing random access at the target cell, thereby reducing mobility interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If random access procedure is performed with target cell for inter-cell mobility, then uplink synchronization is established, but mobility interruption time increases and data rate decreases
Solution Approach 1:
The patent applies preliminary action by pre-establishing timing advance (TA) values with target candidate cells before actual mobility occurs. The UE stores TA values received from serving cells for target cells in advance, so when mobility is triggered, the UE can immediately apply the pre-stored TA value without performing random access procedure, thereby reducing mobility interruption time while maintaining uplink synchronization reliability
Solution Approach 2:
The patent uses the serving cell as an intermediary to transfer TA values to the UE for target cells. Instead of the target cell directly providing TA values through random access, the serving cell acts as a mediator that has already obtained and stored TA values from target cells, enabling the UE to acquire these values without direct interaction with the target cell during mobility events
2Reliability
If random access procedure is performed with target cell, then timing advance is obtained, but network performance is reduced due to interference
Solution Approach 1:
The patent applies preliminary action by pre-acquiring TA values from target cells during normal operation before mobility is needed. The UE stores these pre-obtained TA values for target candidate cells, so when mobility occurs, the UE can immediately apply the stored value without triggering random access procedure that would cause interference, thus maintaining timing advance acquisition reliability while eliminating harmful interference
3Reliability
If TA value is updated frequently to maintain synchronization, then uplink time alignment is improved, but signaling overhead increases
Solution Approach 1:
The patent applies preliminary action by having the network pre-configure and store TA values for target candidate cells in advance. When mobility is triggered, the UE can immediately apply the pre-stored TA value without requiring frequent updates or additional signaling, thereby maintaining uplink time alignment reliability while reducing signaling overhead compared to continuous TA value updates
Data Source
AI summary
According to some embodiments, a method is performed by a wireless device for timing advance (TA) management between the wireless device and at least one target candidate cell for layer one (L1)/layer two (L2) inter-cell mobility. The wireless device is operating in a serving cell different from the target candidate cell. The method comprises: receiving an uplink configuration for a target candidate cell; transmitting an uplink message to the target candidate cell based on the uplink configuration; and receiving a TA value associated with the target candidate cell. The TA value is received in a message from the serving cell.