Seamless Handover in Wireless Networks via PDCP Reordering
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Solution Overview
Problem
In wireless communication networks, seamless handover between base stations is challenging due to out-of-sequence data reception, which can lead to data losses and interruptions, especially during the transfer of Packet Data Convergence Protocol (PDCP) service data units between mobile stations and base stations.
Innovation Solution
The method involves forwarding service data units and sequence number information from a source base station to a target base station during handover, allowing the target base station to reorder and resequence the data for proper transfer to the core network, thereby eliminating the need for resequencing capabilities in the core network and ensuring seamless handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is transferred sequentially from source base station to target base station during handover, then data integrity is maintained, but handover time and interruption duration increase
Solution Approach 1:
The source base station performs preliminary actions by buffering out-of-sequence service data units before handover is complete. This allows the target base station to receive and process data in the correct sequence without waiting for all data to be transmitted, thereby maintaining data integrity while reducing handover interruption time.
2Reliability
If out-of-sequence service data units are buffered at the source base station, then data loss is prevented, but device complexity and processing overhead increase
Solution Approach 1:
The source base station acts as an intermediary by temporarily buffering out-of-sequence service data units and forwarding them in the correct sequence to the target base station. This intermediary buffering function prevents data loss while distributing the reordering complexity across the handover process rather than concentrating it at one point.
3Reliability
If resequencing capability is implemented at the core network, then data sequencing is ensured, but network complexity and processing requirements increase
Solution Approach 1:
The resequencing function is extracted from the core network and relocated to the radio access network, specifically implemented at the base stations during handover. This extraction eliminates the need for resequencing capabilities in the core network while maintaining data sequencing integrity through the source base station's buffering and the target base station's reordering operations.
4Loss of time
If handover is executed quickly without data forwarding, then interruption time is reduced, but data losses and sequencing issues occur
Solution Approach 1:
The handover process maintains continuity of useful action by establishing data forwarding paths between source and target base stations before and during the handover execution. This allows the mobile station to quickly switch base stations while data continues to be forwarded in the background, ensuring both quick handover execution and complete data transfer without losses or sequencing issues.
Data Source
AI summary
A mobile station is configured to support handover from a source base station to a target base station. The mobile station receives signaling from the target base station that indicates Packet Data Convergence Protocol (PDCP) protocol data units which have been successfully received at the target base station. In response, the mobile station generates further PDCP protocol data units for missing PDCP service data units from corresponding PDCP service data units buffered at the mobile station. The generating comprises using a different header compression state from that which was used for the missing PDCP service data units and ciphering specific to a connection with the target base station. The mobile station transmits the further PDCP protocol data units to the target base station.