Downlink Data Coordination for Zero-Millisecond Handover Interruption
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Solution Overview
Problem
Current wireless communication systems, particularly in 5G NR, face challenges in minimizing mobility interruption time during handovers, which is critical for supporting delay-sensitive applications.
Innovation Solution
The proposed solution involves a downlink data coordination procedure that allows a network to indicate when a UE is synchronized to a target cell, enabling direct communication without performing a RACH procedure at the target base station, thereby reducing mobility interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UE performs a RACH procedure at the target base station during handover, then the UE can establish uplink synchronization with the target cell, but the mobility interruption time increases
Solution Approach 1:
The network pre-configures uplink synchronization parameters (timing advance values, uplink grants) at the target base station before the UE arrives. This preliminary preparation eliminates the need for RACH procedure during handover, reducing mobility interruption time while ensuring reliable uplink synchronization establishment.
Solution Approach 2:
The patent extracts the synchronization establishment function from the RACH procedure by using downlink data coordination information to directly provide uplink synchronization parameters. This separates the synchronization function from the random access procedure, enabling faster handover without compromising synchronization reliability.
2Loss of time
If the network implements downlink data coordination procedure, then the mobility interruption time is reduced to near zero milliseconds, but the network complexity increases
Solution Approach 1:
The patent introduces downlink data coordination information as an intermediary mechanism between the source and target base stations. This coordination information carries necessary synchronization parameters and data routing information, enabling the network to coordinate handover without requiring complex direct interaction between base stations and UE, thus reducing network complexity while achieving near-zero mobility interruption.
3Speed
If the UE directly accesses the target cell without RACH procedure, then the handover speed increases, but the risk of access failure increases
Solution Approach 1:
The network performs preliminary validation and preparation by providing pre-configured uplink synchronization parameters and valid uplink grants through downlink data coordination information before the UE attempts direct access. This ensures that when the UE directly accesses the target cell, the access is highly likely to succeed, maintaining reliability while achieving fast handover speed.
Solution Approach 2:
The patent provides beforehand cushioning by pre-configuring multiple uplink grants and synchronization parameters in the downlink data coordination information. This preparation creates a buffer that accommodates potential access conditions, ensuring reliable direct access without requiring RACH fallback procedures.
Data Source
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AI summary
An apparatus for wireless communication, including a memory and at least one processor coupled to the memory. The at least one processor is configured to receive a pre-allocation resource for a target cell via a handover command and transmit a physical layer acknowledgment based on a target cell downlink packet. The at least one processor is also configured to receive an indication for a communication with the target cell in response to the physical layer acknowledgement and access the target cell using the pre-allocated resource based on the indication for the communication with the target cell.