HARQ Retransmission Control for Variable Decoding Latency

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Solution Overview

Problem

Existing HARQ retransmission procedures fail to efficiently manage high performance incremental redundancy retransmission procedures, leading to unnecessary retransmissions of data caused by high decoding latency of retransmissions with low code rates, leading to unnecessary retransmissions, consuming radio resources and increasing interference.

Innovation Solution

Implementing multi-bit HARQ feedback per transport block, allowing receivers to adjust HARQ feedback based on decoding time and load, and transmitters to adjust retransmissions accordingly, reducing unnecessary retransmissions and optimizing resource use.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If incremental redundancy retransmission is used to improve decoding reliability, then transmission reliability is improved, but decoding latency increases causing unnecessary retransmissions

Engineering Contradiction:

Improvetransmission reliabilityVSAvoiddecoding latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic HARQ feedback timing where the receiver adjusts the timing of HARQ feedback based on its current decoding load and processing capability. When decoding latency is high, the receiver delays HARQ feedback transmission to allow sufficient time for decoding incremental redundancy retransmissions, preventing unnecessary retransmissions and optimizing the balance between reliability and latency

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent enhances the feedback mechanism by implementing multi-bit HARQ feedback that conveys not only ACK/NACK information but also decoding status and timing requirements. This enriched feedback allows the transmitter to better understand the receiver's decoding state and adjust subsequent transmissions accordingly, reducing unnecessary retransmissions while maintaining high reliability

Inventive Principle:

Principle #23Feedback

2Device complexity

If HARQ feedback timing is fixed to simplify protocol design, then device complexity is reduced, but system performance deteriorates due to inability to adapt to variable decoding loads

Engineering Contradiction:

Improveprotocol complexityVSAvoidsystem performance

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent transforms the static HARQ feedback timing into a dynamic parameter that adapts to the receiver's decoding load. The receiver determines HARQ feedback timing based on its current processing state, allowing the system to optimize performance under varying conditions while maintaining manageable protocol complexity through standardized adaptation rules

Inventive Principle:

Principle #15Dynamics

3Reliability

If retransmissions are sent without adjusting for receiver decoding status, then transmission completeness is improved, but radio resource efficiency deteriorates due to unnecessary retransmissions

Engineering Contradiction:

Improvetransmission completenessVSAvoidradio resource efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements an enhanced feedback mechanism where the receiver provides multi-bit HARQ feedback indicating its decoding status, including whether it has successfully decoded the transport block or needs incremental redundancy retransmission. This feedback enables the transmitter to send only necessary retransmissions, optimizing radio resource efficiency while ensuring transmission completeness

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies partial retransmission strategy where only the necessary incremental redundancy bits are transmitted based on the receiver's actual decoding needs indicated in the HARQ feedback. Instead of always transmitting complete retransmissions, the system sends only the partial information needed to achieve successful decoding, reducing radio resource consumption

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS20250385762A1HARQ handling for nodes with variable processing times

Publication Date: 2025.12.18 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method for use in a transmitter includes sending a transmission comprising a transport block (TB) comprising a plurality of code blocks (CBs) arranged in one or more code block groups (CBGs). Each code block group includes one or more code blocks and each code block includes a plurality of coded bits. The transmission is sent to a receiver configured to use multi-bit hybrid automatic repeat request (HARQ) feedback per transport block. The method further includes receiving HARQ ACK or NACK feedback from the receiver one or more of the one or more code block groups of the transport block. The method further includes determining a number of code blocks or code block groups to send to the receiver in a retransmission based on at least the received HARQ ACK or NACK feedback.