ACK/NACK Reporting Code Rate Calculation for Cat-M

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Solution Overview

Problem

In Cat-M mechanism, the existing methods for ACK/NACK reporting fail to accurately calculate the number of resource elements (REs) occupied by ACK/NACK on PUSCH, leading to higher PUSCH data code rates and decoding failures, especially in low SINR environments and for CEModeA UE.

Innovation Solution

The method computes the number of REs occupied by ACK/NACK on PUSCH by excluding the OFDM symbols of the guard period, redefining N symb PUSCH – initial to account for unused symbols, thereby reducing the PUSCH data code rate and enhancing decoding performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the number of REs occupied by ACK/NACK is calculated without considering guard period OFDM symbols, then the ACK/NACK transmission uses more REs, but the PUSCH data code rate becomes higher than expected causing decoding failure

Engineering Contradiction:

ImprovePUSCH decoding reliabilityVSAvoidcode rate control precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent extracts and excludes the guard period OFDM symbols from the calculation of available REs for PUSCH data. By identifying and removing these symbols that cannot be used for data transmission, the calculation of PUSCH code rate becomes accurate, preventing code rate exceeding and ensuring reliable decoding.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If the number of ACK/NACK REs is reduced to lower PUSCH code rate, then decoding reliability improves, but ACK/NACK decoding performance deteriorates

Engineering Contradiction:

ImprovePUSCH decoding reliabilityVSAvoidACK/NACK decoding precision

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the calculation parameter by excluding guard period OFDM symbols from the denominator in code rate calculation. This parameter change ensures that the PUSCH code rate is calculated based on actually usable REs, maintaining both PUSCH decoding reliability and ACK/NACK decoding performance without artificial reduction of ACK/NACK REs.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If PUSCH MCS is lowered through BLER control to reduce code rate, then transmission reliability improves, but transmission block size decreases and RBs are wasted

Engineering Contradiction:

ImprovePUSCH transmission reliabilityVSAvoidtransmission efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent performs preliminary action by accurately calculating the available REs for PUSCH data before transmission by excluding guard period symbols. This advance calculation prevents code rate exceeding and ensures reliable decoding without needing to lower MCS through BLER control, thus avoiding reduced transmission block size and RB waste.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentEP3557800B1Method, device and system for ACK/NACK report

Publication Date: 2022.10.19 ALCATEL LUCENT SA

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AI summary

The objective of the present disclosure is to provide a method, apparatus and system of ACK/NACK reporting for Cat-M mechanism. Here, a user equipment feeds back an ACK/NACK message to an eNB on PUSCH based on received downlink data, wherein when computing the number of resource elements occupied by the ACK/NACK message on PUSCH, the number of OFDM symbols in a guard period is ruled out. This may effectively lower the UE's PUSCH data code rate, and meanwhile enhance the eNB's decoding performance on PUSCH.