PDCP Reordering at Handoff Using Sequence Indicators
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Solution Overview
Problem
Current wireless communication systems face significant processing delays during handoff operations due to the inability to maintain in-sequence packet delivery, particularly in LTE systems, where the target base station struggles to determine the correct sequence number for packets after a handover, leading to potential data loss and increased latency.
Innovation Solution
The implementation of indicators such as the first sequence number indication, delta indication, and reset command facilitates lossless and efficient packet sequencing and delivery during handovers by providing the target base station with necessary sequence information, ensuring continuous and timely packet transmission to user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If packet forwarding is performed during handoff without sequence number indication, then handoff speed is improved, but packet sequence continuity is lost causing processing delays
Solution Approach 1:
The source base station performs preliminary action by sending sequence number indication information to the target base station before the actual packet forwarding during handoff. This preliminary exchange of sequence number information enables the target base station to correctly sequence packets without causing processing delays, thus resolving the contradiction between handoff speed and processing time.
Solution Approach 2:
Sequence number indication information acts as an intermediary element between the source base station and target base station. This intermediary carries the necessary sequence context during handoff, allowing the target base station to maintain proper packet sequencing without requiring the UE to reprocess packets, thereby eliminating processing delays while preserving handoff speed.
2Reliability
If sequence number continuity is maintained during handoff, then packet delivery reliability is improved, but device complexity increases due to additional sequencing processing
Solution Approach 1:
The patent extracts the sequence number indication information from the full packet data and transmits it separately as a dedicated control element. This extraction allows the target base station to obtain sequence context without processing the entire packet payload, reducing processing complexity while maintaining packet delivery reliability through correct sequence number tracking.
Solution Approach 2:
The sequence number indication mechanism serves multiple functions: it provides sequence context for packet ordering, enables reliability checking, and simplifies the target base station's processing by providing pre-computed sequence information. This multi-functionality achieves reliable packet delivery without proportionally increasing device complexity.
3Measurement precision
If the target base station waits for sequence number information before forwarding packets, then packet sequencing accuracy is improved, but handoff time is increased
Solution Approach 1:
The source base station sends sequence number indication information to the target base station in advance before packet forwarding begins. This preliminary action ensures the target base station has all necessary sequence context ready, allowing immediate accurate packet sequencing without waiting, thus achieving both high sequencing accuracy and minimal handoff time.
Solution Approach 2:
The sequence number indication mechanism enables continuous and accurate packet sequencing throughout the handoff process without interruption. By maintaining the sequence number context continuously from source to target base station, the system achieves accurate packet ordering while eliminating delays that would otherwise extend handoff duration.
Data Source
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AI summary
Systems and methodologies are described that facilitate management of data delivery and processing in a wireless communication system and, more particularly, that support Packet Data Convergence Protocol (PDCP) reordering of packets during a handoff operation. Various aspects described herein can mitigate processing delays associated with PDCP reordering of packets at handoff by determining, communicating, and/or otherwise identifying one or more indicators during handoff that facilitate lossless communication of packets to a terminal with minimal delay. These indicators can include sequence number information for a source Node B, information regarding a step or jump size applied to a sequence number by a target Node B, a reset command, and/or other suitable indicators.