HARQ Feedback Control for Time-Alignment Timer Expiry in LTE

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Solution Overview

Problem

In wireless communication systems like E-UMTS and LTE, downlink HARQ operations are hindered when the time alignment timer is not running or has expired, leading to potential synchronization failures and wastage of radio resources due to incorrect ACK/NACK signaling.

Innovation Solution

The method involves the mobile terminal discarding received data and not sending HARQ feedback when not time-aligned with the base station, and proposing to decode data without transmitting feedback, while also managing the HARQ soft buffer by flushing or replacing data based on successful decoding and timer status.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the mobile terminal continues HARQ feedback transmission when the time alignment timer is expired or not running, then the downlink data reception can proceed, but synchronization failures occur and radio resources are wasted due to incorrect ACK/NACK signaling

Engineering Contradiction:

Improvedownlink data reception continuityVSAvoidsynchronization accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The mobile terminal checks the time alignment timer status before transmitting HARQ feedback. This preliminary check prevents synchronization failures by ensuring the terminal only sends feedback when properly time-aligned with the base station, avoiding wasted radio resources from incorrect ACK/NACK signaling while maintaining continuous downlink data reception when aligned.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If the mobile terminal transmits HARQ feedback when not time-aligned, then feedback transmission is maintained, but radio resources are wasted and synchronization failures occur

Engineering Contradiction:

ImproveHARQ feedback transmissionVSAvoidradio resource consumption

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The mobile terminal autonomously monitors its own time alignment timer status and makes decisions about HARQ feedback transmission based on this self-assessed synchronization state. This self-service mechanism prevents waste of radio resources by ensuring feedback is only transmitted when the terminal is properly time-aligned, eliminating incorrect ACK/NACK signaling without external control.

Inventive Principle:

Principle #25Self-service

3Productivity

If the mobile terminal sends ACK/NACK signals when the time alignment timer is expired, then HARQ operation continues, but synchronization failures occur leading to incorrect feedback

Engineering Contradiction:

ImproveHARQ operation continuityVSAvoidfeedback accuracy

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The mobile terminal takes preliminary action to prevent incorrect feedback by checking the time alignment timer status before sending ACK/NACK signals. This preliminary anti-action blocks the transmission of potentially incorrect feedback when the timer is expired or not running, preventing synchronization failures and maintaining HARQ operation continuity only when properly synchronized.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentEP2248293B1Method of downlink HARQ operation at an expiry of time alignment timer

Publication Date: 2019.04.17 LG ELECTRONICS INC

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AI summary

Disclosed is the radio (wireless) communication system providing a radio communication service and the terminal, and more particularly, to a method of a downlink HARQ (Hybrid Automatic Repeat reQuest) operation of terminal that is not time-aligned with the base station in an Evolved Universal Mobile Telecommunications System (E-UMTS) evolved from the Universal Mobile Telecommunications System (UMTS) or a Long Term Evolution (LTE) system.