RLC Handover Data Loss Prevention via Out-of-Sequence Transmission

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Solution Overview

Problem

During handover in wireless communication, the RLC and PDCP layers experience data loss due to the inability to transfer SDUs in sequence, leading to wasted radio resources and delayed transmission efficiency.

Innovation Solution

Informing the lower layers about the handover time point allows them to generate and transmit data blocks out of sequence, ensuring data transfer without loss, thereby reducing re-transmission overhead and control signal overhead.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the RLC layer transfers SDUs in sequence during handover, then data integrity is maintained, but transmission efficiency is degraded and radio resources are wasted due to re-transmission requests

Engineering Contradiction:

Improvedata integrityVSAvoidtransmission efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The source base station performs preliminary actions by forwarding downlink data to the target base station before handover completion, and the target base station pre-prepares data for transmission. This allows the target base station to immediately transmit data after handover without waiting for re-transmission requests, thereby maintaining data integrity while improving transmission efficiency and avoiding radio resource waste.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The target base station acts as an intermediary by receiving and buffering downlink data from the source base station before handover completion, and by receiving uplink data from the UE out of sequence and reordering it. This intermediary role enables seamless data flow during handover without requiring sequential transfer, thus maintaining reliability while improving productivity.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the RLC layer waits for handover completion before transferring data, then data loss is prevented, but transmission delay increases

Engineering Contradiction:

Improvedata loss preventionVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The source base station forwards downlink data to the target base station in advance before handover completion, and the target base station prepares data for immediate transmission. This preliminary action ensures data is ready when handover completes, preventing data loss while minimizing transmission delay.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The target base station continuously receives and processes data from the source base station and from the UE during handover, maintaining continuous useful action rather than pausing for handover completion. This ensures no data loss while avoiding transmission delays.

Inventive Principle:

Principle #20Continuity of useful action

3Reliability

If the PDCP layer requests re-transmission of downlink data after handover, then data integrity is restored, but radio resources are wasted

Engineering Contradiction:

Improvedata integrity restorationVSAvoidradio resource waste

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The source base station forwards downlink data to the target base station before handover completion, and the target base station pre-prepares data for transmission. This eliminates the need for PDCP layer re-transmission requests after handover, thereby restoring data integrity without wasting radio resources.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention converts the potential harm of data loss during handover into a benefit by implementing forward data transmission and out-of-sequence data handling. This approach ensures data integrity is maintained proactively rather than through reactive re-transmission, eliminating radio resource waste while restoring data integrity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9681355B2Method for performing handover procedure and creating data

Publication Date: 2017.06.13 VIVO MOBILE COMM CO LTD

AI summary

A method is presented for performing handover by a mobile terminal from a source base station to a target base station. The mobile terminal has a Radio Resource Control (RRC) layer and a Radio Link Control (RLC) layer. A handover command is received at the RRC layer of the mobile terminal. An indication associated with the handover command is received at the RLC layer of the mobile terminal. At least one RLC service data unit (SDU) from at least one protocol data unit (PDU) having a sequence number that is less than a higher edge of a window of the mobile terminal is reassembled at the RLC layer of the mobile terminal. The reassembled at least one RLC SDU to an upper layer of the mobile terminal is delivered at the RLC layer of the mobile terminal.