Source Access Node Triggers for Early Downlink Forwarding

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Solution Overview

Problem

Existing handover solutions in wireless communication networks, particularly in LTE and NR, fail to reduce downlink data transfer latency and are susceptible to connection loss during make-before-break handovers, especially for UEs with single Tx/Rx chains, leading to delayed DL data forwarding and potential packet loss.

Innovation Solution

Implementing a trigger mechanism for downlink data forwarding at the source access node based on predefined criteria, such as receipt of a response message from the target access node or successful transmission of a message by the UE, allowing earlier initiation of data forwarding before the RRC Connection Reconfiguration Complete message is sent.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If make-before-break handover is implemented, then connection continuity is improved, but downlink data transfer latency increases and packet loss occurs

Engineering Contradiction:

Improveconnection continuityVSAvoiddownlink data transfer latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The source access node forwards downlink data to the target access node before the UE completes handover to the target cell. This preliminary data forwarding action ensures that data is already available at the target node when the UE switches cells, eliminating waiting time and reducing latency while maintaining connection continuity through the make-before-break approach

Inventive Principle:

Principle #10Preliminary action

2Loss of time

If data forwarding is initiated earlier, then downlink data transfer latency is reduced, but connection stability deteriorates due to potential connection loss during handover

Engineering Contradiction:

Improvedownlink data transfer latencyVSAvoidconnection stability

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The target access node acts as an intermediary that receives and buffers downlink data from the source access node before the UE completes handover. This intermediary mechanism allows early data forwarding to reduce latency while the target node holds the data safely until the UE is successfully connected to the target cell, thereby maintaining connection stability

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If trigger mechanism is implemented for early data forwarding, then productivity is improved, but device complexity increases

Engineering Contradiction:

Improvedata forwarding efficiencyVSAvoidhandover control mechanism complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The handover control mechanism uses parameter changes, specifically triggering data forwarding based on the reception of the RRC Connection Reconfiguration Complete message from the UE. This parameter-based trigger (message reception event) automates the data forwarding decision, improving productivity through efficient timing while avoiding excessive complexity by using a clear, well-defined trigger condition

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12438653B2Access node, user equipment and methods in a wireless communications network

Publication Date: 2025.10.07 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method performed by a source access node for performing data forwarding at handover of a UE from a source cell to a target cell in a wireless communications network is provided. When a criterion for data forwarding is fulfilled, the source access node obtains a trigger for downlink data forwarding. When receiving the trigger, the source access node initiates downlink data forwarding to the UE via the target access node.