HARQ Buffer Flush for Failure Detection in LTE

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Solution Overview

Problem

The existing HARQ failure detection mechanism in wireless telecommunications systems, particularly in LTE, fails to correctly detect transmission failures when transmissions are suspended, leading to improper functioning and increased data latency due to incorrect feedback from base stations.

Innovation Solution

A method and transceiver configuration that detect HARQ transmission failures by flushing the HARQ buffer when the maximum number of transmissions is reached and identifying failures based on the last received HARQ feedback, which differs from a valid ACK, ensuring accurate notification to upper layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the base station sends a positive HARQ ACK to suspend uplink transmissions, then the probability of collision is reduced, but the HARQ failure detection mechanism fails to correctly detect transmission failures

Engineering Contradiction:

Improvecollision probabilityVSAvoidHARQ failure detection accuracy

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The base station performs a preliminary action by sending a positive HARQ ACK to suspend uplink transmissions before actual collisions occur. This proactive suspension prevents potential collisions by stopping transmissions that might interfere with ongoing operations, while the invention ensures failure detection remains accurate by tracking the suspension state separately.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention introduces an intermediary mechanism - a suspension indicator or state tracker - that mediates between the suspended transmission state and the HARQ failure detection logic. This intermediary allows the system to recognize when a positive ACK is sent for suspension purposes rather than indicating actual successful reception, thereby maintaining detection accuracy despite the suspension action.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the HARQ transmitter relies on HARQ feedback for failure detection, then fast error detection is enabled, but transmission failures during suspension are not correctly identified

Engineering Contradiction:

Improveerror detection speedVSAvoidfailure detection accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The system uses HARQ feedback (ACK/NACK) for fast error detection, maintaining the speed advantage. The invention enhances this feedback mechanism by adding contextual information - specifically tracking whether the transmitter is in a suspended state - to the feedback interpretation logic, enabling accurate failure detection despite suspension activities.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention introduces dynamic state tracking for the HARQ transmitter, where the detection mechanism adapts its behavior based on the current transmission state (suspended or active). This dynamic adjustment allows the system to maintain fast detection speed while improving accuracy by recognizing that positive ACKs during suspension do not indicate successful reception.

Inventive Principle:

Principle #15Dynamics

3Object-affected harmful factors

If the eNodeB suspends uplink transmissions by sending positive HARQ ACK, then transmission collisions are avoided, but data latency increases due to improper buffer utilization

Engineering Contradiction:

Improvecollision probabilityVSAvoiddata latency

Core Design Contradiction:

Object-affected harmful factorsVSLoss of time

Solution Approach 1:

The eNodeB performs preliminary suspension by sending positive HARQ ACKs before collisions occur, preventing harmful interference. The invention complements this by implementing proper buffer management that clears or marks suspended data appropriately, preventing the buffer from holding stale data that would cause unnecessary latency when resuming transmissions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention applies the discarding principle to HARQ buffers during suspension - when a positive ACK is sent for suspension purposes, the corresponding buffer content is properly discarded or marked as invalid. This prevents the buffer from retaining outdated data that would cause latency issues upon resumption, while still allowing the suspension mechanism to prevent collisions during active transmission periods.

Inventive Principle:

Principle #34Discarding and recovering

Data Source

PatentUS8897149B2Method and a transceiver for HARQ failure detection

Publication Date: 2014.11.25 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The present invention relates to a method and to a transceiver (400) for detecting HARQ transmission failure in a telecommunications system. The transceiver (400) is arranged to execute a HARQ process which is used to generate a transmission of data units to e.g. a eNodeB. The transceiver is also arranged to determine when a maximum number of transmission attempts is reached and when this occurs to flush a HARQ buffer associated with the HARQ process and to detect that a HARQ transmission failure has occurred when the last HARQ feedback received for the current HARQ process is not a HARQ ACK.