HARQ Retransmission Deferral After CQI-Only Report

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Solution Overview

Problem

In LTE wireless communication systems, suspending a hybrid automatic repeat request (HARQ) process due to a CQI-only grant requires an adaptive uplink grant to resume, which consumes scarce control signaling resources and increases error probabilities, or delaying information element transmission if multiplexing is not prohibited, leading to increased transmission delays.

Innovation Solution

Automatically defer synchronous HARQ retransmissions to a later transmission interval when a CQI-only grant is received, eliminating the need for an adaptive uplink grant to resume the process, and maintaining transparency to the MAC layer by retaining HARQ feedback and scheduling retransmissions based on NACK messages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an adaptive uplink grant is sent to resume the HARQ process after suspension, then the HARQ process can be resumed, but control signaling resources are consumed and error probabilities increase

Engineering Contradiction:

ImproveHARQ process resumption reliabilityVSAvoidcontrol signaling resources

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The HARQ process automatically resumes using the buffered NACK feedback without requiring an explicit adaptive uplink grant from the base station. The UE autonomously retransmits the data block in the next available transmission opportunity, eliminating the need for additional control signaling to resume the process.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system prepares and buffers the NACK feedback and retransmission data in advance when the HARQ process is suspended. This preliminary preparation allows the process to resume immediately without requiring additional signaling, as all necessary information is already ready for automatic resumption.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If information element transmission is delayed to avoid multiplexing conflicts, then transmission errors are reduced, but transmission delays increase

Engineering Contradiction:

Improvetransmission error rateVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system dynamically adjusts the transmission timing based on the HARQ process state. When suspension is detected, the retransmission is automatically scheduled for the next available transmission opportunity rather than being fixed or delayed arbitrarily, optimizing the balance between avoiding conflicts and minimizing delay.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8892978B2HARQ process continuation after CQI-only report

Publication Date: 2014.11.18 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Techniques for controlling synchronous HARQ retransmissions are disclosed, in which non-adaptive retransmissions scheduled for a first transmission time interval are automatically deferred to a later transmission time interval in the event that a control message prohibiting the retransmission during the first transmission interval is received. In an exemplary method, a NACK message is received in response to a previous data transmission corresponding to a stop-and-wait HARQ process, and a synchronous HARQ retransmission is scheduled for a first transmission interval in response. A control message indicating that data for the stop-and-wait HARQ process may not be sent during the first transmission interval is received, and the synchronous HARQ retransmission is automatically deferred to a second transmission interval, responsive to the control message. An explicit grant is not required to trigger the retransmission during the second transmission interval.