LTE-MTC HARQ-ACK Delay Scheduling Across Repetitions and Gaps

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Solution Overview

Problem

The introduction of 14 HARQ processes in DL for HD-FDD Cat M1 UEs in LTE-MTC does not consider further delays caused by coexistence with PUCCH repetitions, invalid BL/CE DL subframes, invalid BL/CE UL subframes, and measurement gaps, which impact HARQ-ACK delays.

Innovation Solution

A selective HARQ-ACK delay counting strategy is implemented, incorporating PUCCH repetitions, invalid BL/CE DL subframes, and measurement gaps, using a method to determine HARQ-ACK scheduling counting strategies and adjust HARQ-ACK delay values accordingly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If 14 HARQ processes are introduced in DL for HD-FDD Cat M1 UEs, then peak data rate is improved, but scheduling delay and HARQ-ACK delay increase due to coexistence with PUCCH repetitions, invalid BL/CE DL subframes, invalid BL/CE UL subframes, and measurement gaps

Engineering Contradiction:

Improvepeak data rateVSAvoidscheduling delay

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent implements dynamic HARQ-ACK delay adjustment by introducing multiple delay values (K1, K2, K3) that are selected based on current system conditions such as PUCCH repetition status, measurement gap configuration, and invalid subframe patterns. This allows the scheduling delay to adapt dynamically rather than being fixed, resolving the contradiction between achieving high peak data rate with 14 HARQ processes and managing the resulting scheduling delays.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of HARQ-ACK delay by introducing multiple configurable delay values (K1=4, K2=5, K3=6, etc.) instead of a single fixed delay. The appropriate delay value is selected based on the specific combination of PUCCH repetitions, measurement gaps, and invalid subframes present, allowing the system to optimize the trade-off between peak data rate achievement and scheduling delay management.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If 14 HARQ processes are introduced in DL, then peak data rate is improved, but device complexity increases due to need to manage additional delay parameters and counting strategies

Engineering Contradiction:

Improvepeak data rateVSAvoidscheduling complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent segments the HARQ-ACK delay management into distinct cases based on the presence or absence of specific conditions (PUCCH repetitions, measurement gaps, invalid subframes). Each segment has predetermined delay values and counting strategies, which simplifies the overall complexity by breaking down the complex scheduling problem into manageable, condition-specific segments rather than requiring a single complex solution for all scenarios.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent establishes preliminary rules and procedures for determining HARQ-ACK delays based on pre-configured parameters and conditions. The delay values and counting strategies are determined in advance based on the specific combination of PUCCH repetitions, measurement gaps, and invalid subframes, rather than being calculated dynamically in real-time, which reduces the computational complexity at the moment of scheduling decisions.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If HARQ-ACK delay values are adjusted to accommodate 14 HARQ processes, then scheduling flexibility is improved, but reliability decreases due to increased delay variability

Engineering Contradiction:

Improvescheduling flexibilityVSAvoidHARQ-ACK timing reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent incorporates feedback mechanisms where the selected HARQ-ACK delay value is determined based on feedback about current system conditions (PUCCH repetition status, measurement gap presence, invalid subframe patterns). This feedback-driven approach ensures that the delay adjustment maintains reliability by selecting appropriate delay values that account for the actual system state, rather than using arbitrary delay variations.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP4169313B1Method, apparatus and computer program product for scheduling delay associated with HARQ processes in LTE-mtc

Publication Date: 2025.09.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

The present application generally relates to wireless communication technology. More particularly, the present application relates to a method and apparatus for scheduling delay associated with HARQ processes in LTE-MTC. The present application also relates to computer program product adapted for the same purpose. According to one embodiment, a method for scheduling delay associated with HARQ processes in LTE-MTC comprises: -a) in response to presence or non-presence of PUCCH repetition, invalid BL/CE DL subframe, invalid BL/CE UL subframe, and measurement gap, determining a HARQ-ACK scheduling counting strategy; and-b) scheduling a HARQ-ACK delay value in accordance with the HARQ-ACK scheduling counting strategy.