HARQ ACK/NACK Bundling via Duration Prioritization

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Solution Overview

Problem

In Long Term Evolution (LTE) and New Radio (NR) wireless communication systems, HARQ ACK/NACK bundling leads to performance loss due to retransmission of correctly received Transport Blocks, especially when spatial-domain bundling results in a NACK bit, causing unnecessary retransmission of correctly received data.

Innovation Solution

The method involves prioritizing HARQ ACK/NACK bits based on their data transmission duration, bundling those with shorter durations first to minimize performance loss, and allowing time-domain bundling only when spatial-domain bundling is insufficient to meet the capacity requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If HARQ ACK/NACK bits are bundled using AND operation to reduce the number of bits to match UCI format capacity, then the number of bits to be transmitted is reduced, but correctly received Transport Blocks are retransmitted causing performance loss

Engineering Contradiction:

Improvenumber of HARQ ACK/NACK bitsVSAvoidcorrect reception of Transport Blocks

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent segments the bundling process into two distinct phases: spatial-domain bundling (grouping bits within the same time resource but different spatial layers) and time-domain bundling (grouping bits across different time resources). This segmentation allows selective application of bundling operations, preventing unnecessary retransmissions by avoiding time-domain bundling when spatial bundling alone suffices to reduce bit count to UCI capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces dynamic selection between spatial-domain and time-domain bundling based on channel conditions and traffic characteristics. The system adaptively chooses which bundling dimension to apply, transitioning from static mandatory time-domain bundling to flexible dynamic selection, thereby optimizing the balance between bit reduction and maintaining transmission reliability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If spatial-domain bundling is prioritized over time-domain bundling to reduce retransmissions, then performance loss is reduced, but the UCI format capacity may still be insufficient to carry all HARQ ACK/NACK bits

Engineering Contradiction:

Improveretransmission efficiencyVSAvoidnumber of HARQ ACK/NACK bits

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent divides the bundling operation into sequential stages: first spatial-domain bundling is applied to minimize performance loss, then if the bit count still exceeds UCI capacity, time-domain bundling is applied as a secondary reduction mechanism. This segmented approach ensures both reliability optimization and capacity compliance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial bundling selectively - not all bits are bundled in the same manner. Instead, spatial bundling is applied partially to groups of bits where it benefits reliability, while time-domain bundling is applied partially only when necessary to meet capacity constraints, avoiding excessive bundling that would cause unnecessary retransmissions.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of operation

If time-domain bundling is applied to bundle HARQ ACK/NACK bits from multiple downlink subframes into one uplink subframe, then the transmission timing is simplified, but correctly received TBs may be retransmitted due to spatial channel correlation

Engineering Contradiction:

Improvetransmission timing managementVSAvoidcorrect reception of Transport Blocks

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent segments the bundling hierarchy so that spatial-domain bundling (within same time, different layers) takes precedence over time-domain bundling (across different times). By separating these bundling dimensions and applying them in sequence, the patent avoids direct time-domain bundling of spatially correlated bits, thereby preventing unnecessary retransmissions while still achieving timing simplification when needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent performs spatial-domain bundling as a preliminary action before time-domain bundling. This preliminary spatial grouping reduces the bit count and eliminates spatially correlated redundancy first, so that subsequent time-domain bundling operates on already-optimized bit sets, minimizing the risk of retransmitting correctly received TBs.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP3711453B1Methods and devices for hybrid automatic repeat request acknowledgement/non-acknowledgement bundling

Publication Date: 2023.10.04 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

A method (300) at a terminal device capable of Hybrid Automatic Repeat reQuest, HARQ, Acknowledgement/Non-Acknowledgement, ACK/NACK, bundling, the method (300) includes: determining that a number of HARQ ACK/NACK bits to be transmitted is larger than a predetermined capacity(310); and bundling at least two of the number of HARQ ACK/NACK bits based on a data transmission duration associated with each of the number of HARQ ACK/NACK bits(320).