Bundled Feedback Transmission in Wireless Networks

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Solution Overview

Problem

In wireless cellular communication networks, especially in TDD systems, the inefficiency in transmitting ACK/NAK bits for hybrid ARQ operations leads to increased data transmission overhead due to the mismatch between the number of downlink and uplink subframes, necessitating a method to reduce the number of bits transmitted while ensuring reliable feedback.

Innovation Solution

Implementing ACK/NAK bundling, where multiple ACK/NAK bits are compressed into one or two bits and transmitted in the corresponding uplink subframe, along with the use of a toggle bit or M-bit field in DL grants to detect missed subframes and facilitate discontinuous transmission (DTX) when necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple ACK/NAK bits are transmitted separately for each downlink subframe, then feedback reliability is improved, but transmission overhead increases

Engineering Contradiction:

Improvefeedback reliabilityVSAvoidtransmission overhead

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent combines multiple ACK/NAK bits into a single bundled feedback transmission. Instead of transmitting separate ACK/NAK bits for each downlink subframe, the UE bundles multiple ACK/NAK responses into one composite feedback message transmitted in the uplink, thereby reducing transmission overhead while maintaining feedback functionality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent segments the feedback transmission by introducing a Downlink Assignment Indicator (DAI) field in each downlink grant that divides the downlink subframes into manageable groups. This segmentation allows the receiver to track and bundle ACK/NAK responses systematically across multiple subframes, enabling efficient compression of feedback bits

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If ACK/NAK bundling is implemented to reduce bits, then transmission overhead is reduced, but detection of missed subframes becomes more difficult

Engineering Contradiction:

Improvenumber of bits transmittedVSAvoiddetection of missed subframes

Core Design Contradiction:

Quantity of substanceVSDifficulty of detecting and measuring

Solution Approach 1:

The patent implements preliminary action by embedding the Downlink Assignment Indicator (DAI) field in each downlink grant before the actual data transmission. This DAI field contains counter information that allows the UE to pre-validate the reception of downlink grants and detect missed subframes before generating the bundled ACK/NAK feedback, thus solving the detection difficulty inherent in bundling

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses feedback mechanisms where the DAI counter value in received downlink grants is compared against expected values. When discrepancies are detected, the UE can identify missed subframes and adjust its bundled feedback accordingly, creating a closed-loop system that maintains detection capability despite bit compression

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8345605B2Transmission of bundled feedback in wireless networks

Publication Date: 2013.01.01 APPLE INC

AI summary

A transmission of information between a secondary to a primary node in a wireless network occurs in a plurality of N logical time durations. Bundled feedback information for multiple DL transmissions is provided in one UL transmission. Each DL transmission is indicated by a DL grant comprising an M-bit downlink assignment indicator (DAI) field. The primary node increments the value of the M-bit DAI field in successively transmitted DL grants. The secondary node examines the value of the M-bit DAI field in received DL grants, to determine the bundled feedback information.