HARQ Feedback Bundling for TDD Fixed and Flexible Subframes

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Solution Overview

Problem

Current ACK/NACK bundling methods in TDD systems face inefficiencies due to differing interference conditions between fixed and flexible subframes, leading to potential throughput loss and challenges in error correction in scenarios like eIMTA, where downlink channel conditions vary significantly.

Innovation Solution

The method involves bundling feedback into at least two sets of information based on differently timed windows defined by subframe types, allowing for separate error determination and improved resource utilization by distinguishing between fixed and flexible subframes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If ACK/NACK bundling is applied to reduce feedback payload, then overhead is reduced, but throughput is lost due to inability to distinguish error sources between fixed and flexible subframes

Engineering Contradiction:

Improvefeedback overheadVSAvoidthroughput

Core Design Contradiction:

Loss of substanceVSProductivity

Solution Approach 1:

The feedback bundling is segmented into separate bundles for fixed subframes and flexible subframes. This allows the system to reduce overall feedback overhead while maintaining the ability to identify error sources by bundle type, thus preventing unnecessary throughput loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different bundling strategies are applied to different subframe types based on their local characteristics. Fixed subframes use one bundling approach while flexible subframes use another, allowing optimization for each local condition rather than a uniform approach.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If separate feedback is sent for each subframe to maintain accuracy, then error correction precision is improved, but feedback overhead increases

Engineering Contradiction:

Improveerror detection accuracyVSAvoidfeedback overhead

Core Design Contradiction:

Measurement precisionVSLoss of substance

Solution Approach 1:

Instead of sending complete separate feedback for every single subframe, the system applies partial bundling where multiple subframes are grouped. This reduces the excessive amount of feedback overhead while maintaining sufficient error detection accuracy through the bundled structure.

Inventive Principle:

Principle #16Partial or excessive action

3Adaptability or versatility

If flexible UL-DL reconfiguration is implemented for traffic adaptation, then system adaptability is improved, but interference conditions become more variable and complex

Engineering Contradiction:

Improvetraffic adaptation capabilityVSAvoidinterference variability

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The system segments feedback handling into different bundles for fixed and flexible subframes. This segmentation allows the system to accommodate variable interference conditions in flexible subframes while maintaining stable feedback mechanisms for fixed subframes, thus supporting traffic adaptation without being overwhelmed by interference variability.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP3050236B1Bundling HARQ feedback in a time division duplexing communication system

Publication Date: 2020.07.29 NOKIA SOLUTIONS & NETWORKS OY

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AI summary

Feedback determined for a plurality of subframes within a time window in a time division duplex system is bundled into at least two sets of feedback information based on differently timed bundling windows defined based on subframe types. When feedback associated with the plurality of subframes is received, possible errors in the subframes is determined based on the at least two sets of feedback information.