Seamless Handover via Sequence Reordering in Wireless Networks
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Solution Overview
Problem
Seamless handover in wireless communication networks is compromised by out-of-sequence data reception, which complicates mobile station handover between base stations, leading to potential data losses and interruptions.
Innovation Solution
The method involves forwarding sequence number information from the source base station to the target base station during handover, allowing for reordering of out-of-sequence service data units, thereby ensuring sequential transfer to the core network without requiring re-sequencing capabilities in the core network. This includes identifying missing data units and requesting retransmissions from the mobile station to complete the sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station buffers out-of-sequence data to maintain sequential transfer, then data sequence integrity is improved, but handover complexity and interruption time increase
Solution Approach 1:
The patent extracts the re-sequencing function from the core network and relocates it to the target base station. The target base station receives out-of-sequence service data units from the source base station, re-sequences them locally, and then forwards them to the core network in proper sequence. This extraction eliminates the need for core network re-sequencing capabilities and reduces handover complexity while maintaining data integrity.
Solution Approach 2:
The target base station acts as an intermediary between the source base station and the core network during handover. It receives service data units from the source base station, performs re-sequencing operations, and then forwards the properly ordered data to the core network. This intermediary role enables seamless handover by handling re-sequencing at the radio access boundary rather than requiring core network involvement.
2Reliability
If the core network performs re-sequencing of service data units, then data sequence integrity is improved, but core network complexity and processing overhead increase
Solution Approach 1:
The patent explicitly extracts the re-sequencing function from the core network and places it at the target base station. The target base station is equipped with a re-sequencer that receives out-of-sequence service data units from the source base station, re-sequences them, and forwards them to the core network in the correct sequence. This eliminates the need for re-sequencing capabilities in the core network while maintaining data integrity.
3Reliability
If the mobile station retransmits missing protocol data units after handover, then data completeness is improved, but handover interruption time increases
Solution Approach 1:
The patent implements preliminary action by having the target base station request missing service data units from the mobile station during the handover process, before the handover is fully complete. The target base station identifies which service data units are missing based on sequence numbers and requests their retransmission from the mobile station's buffer. This allows the handover to proceed while simultaneously recovering missing data, reducing overall interruption time.
Solution Approach 2:
The patent maintains continuity of useful action by enabling the target base station to continue receiving and processing service data units from the mobile station even during the handover transition. The mobile station continues to transmit data to the target base station using its existing buffer, and the target base station processes this data while simultaneously requesting any missing units, ensuring continuous data flow throughout the handover process.
Data Source
AI summary
In a wireless communication network where base stations receive protocol data units (PDUs) from mobile stations for decompression and deciphering for ordered, sequential transfer as service data units (SDUs) to an associated core network, the teachings presented herein provide a method of supporting seamless handover of a mobile station from a source base station to a target base station. By way of example, the teachings herein apply to a network based on the E-UTRA specifications, as promulgated by the 3GPP. However, that example is non-limiting, as the teachings herein apply to any network that employs in-sequence data delivery and duplicate data detection at handover. Broadly, the source base station forwards out-of-sequence SDUs and corresponding sequence number information to the target base station in support of seamless handover, and the target base station uses that information to request retransmissions as needed for packet reordering.